From 3a8d937ee670d627679471be4ac7d9bc6366ead9 Mon Sep 17 00:00:00 2001
From: Cyrus Najmabadi <cyrusn@microsoft.com>
Date: Fri, 30 May 2025 22:44:20 +0200
Subject: [PATCH 01/26] Add file

---
 src/Code.txt                                  | 310 ++++++++++++++++++
 .../Parsing/RangeExpressionParsingTests.cs    |   9 +
 2 files changed, 319 insertions(+)
 create mode 100644 src/Code.txt

diff --git a/src/Code.txt b/src/Code.txt
new file mode 100644
index 0000000000000..69836fb76ac7e
--- /dev/null
+++ b/src/Code.txt
@@ -0,0 +1,310 @@
+// ------------------------------
+//	THIS FILE IS AUTO GENERATED
+// PLEASE DO NOT MODIFY 
+// ------------------------------
+// Hash: D5-B1-B5-D5-B6-27-C1-44-E0-20-77-14-52-A7-7A-E3-26-1C-6C-74-82-E1-2D-00-C3-73-22-7D-F5-CF-1B-76-95-45-88-4A-9A-0D-E3-D1-8F-69-F3-C3-76-41-92-67-F1-9D-64-EF-86-77-39-48-8C-0E-20-44-51-CA-5D-65
+
+using Foobar.Combat;
+using Foobar.Commons.Rules;
+using Foobar.Localization;
+using Foobar.Shared.Entities.Units;
+using static System.Collections.Immutable.ImmutableArray;
+using System;
+using System.Collections.Immutable;
+using Foobar.Shared.Utils;
+using System.Collections.Generic;
+using Foobar.GeneratedCode;
+
+namespace Foobar;
+
+
+[GenerateAllValues(typeof(Foobar.Commons.Rules.UnitEquipmentAttributeDefinition))]
+public static partial class EquipmentAttributes
+{
+
+    public static class Minor_Power_Flat
+    {
+        public static readonly UnitEquipmentAttributeDefinition Instance = new(
+        	Id: "Minor_Power_Flat",
+        	Attribute: CombatAttribute.Power,
+        	ModifierType: AttributeModifierType.Flat,
+        	PrimaryStatsByLevel: null,
+        	SecondaryStatByRarityFrom: Create(30.0, 60.0, 110.0, 180.0, 280.0),
+        	SecondaryStatByRarityTo: Create(40.0, 80.0, 140.0, 220.0, 320.0),
+        	CalibrationStatsByLevel: null,
+        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
+    }
+
+    public static class Minor_Power_Perc
+    {
+        public static readonly UnitEquipmentAttributeDefinition Instance = new(
+        	Id: "Minor_Power_Perc",
+        	Attribute: CombatAttribute.Power,
+        	ModifierType: AttributeModifierType.Percentage,
+        	PrimaryStatsByLevel: null,
+        	SecondaryStatByRarityFrom: Create(.02, .04, .06, .09, .13),
+        	SecondaryStatByRarityTo: Create(.03, .05, .08, .12, .16),
+        	CalibrationStatsByLevel: null,
+        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
+    }
+
+    public static class Minor_CritChance_Flat
+    {
+        public static readonly UnitEquipmentAttributeDefinition Instance = new(
+        	Id: "Minor_CritChance_Flat",
+        	Attribute: CombatAttribute.CritChance,
+        	ModifierType: AttributeModifierType.Flat,
+        	PrimaryStatsByLevel: null,
+        	SecondaryStatByRarityFrom: Create(.02, .04, .06, .09, .13),
+        	SecondaryStatByRarityTo: Create(.03, .05, .08, .12, .16),
+        	CalibrationStatsByLevel: null,
+        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
+    }
+
+    public static class Minor_CritBoost_Flat
+    {
+        public static readonly UnitEquipmentAttributeDefinition Instance = new(
+        	Id: "Minor_CritBoost_Flat",
+        	Attribute: CombatAttribute.CritBoost,
+        	ModifierType: AttributeModifierType.Flat,
+        	PrimaryStatsByLevel: null,
+        	SecondaryStatByRarityFrom: Create(.02, .04, .06, .09, .13),
+        	SecondaryStatByRarityTo: Create(.03, .05, .08, .12, .16),
+        	CalibrationStatsByLevel: null,
+        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
+    }
+
+    public static class Minor_Defense_Flat
+    {
+        public static readonly UnitEquipmentAttributeDefinition Instance = new(
+        	Id: "Minor_Defense_Flat",
+        	Attribute: CombatAttribute.Defense,
+        	ModifierType: AttributeModifierType.Flat,
+        	PrimaryStatsByLevel: null,
+        	SecondaryStatByRarityFrom: Create(40.0, 100.0, 170.0, 280.0, 380.0),
+        	SecondaryStatByRarityTo: Create(60.0, 120.0, 210.0, 330.0, 480.0),
+        	CalibrationStatsByLevel: null,
+        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
+    }
+
+    public static class Minor_Defense_Perc
+    {
+        public static readonly UnitEquipmentAttributeDefinition Instance = new(
+        	Id: "Minor_Defense_Perc",
+        	Attribute: CombatAttribute.Defense,
+        	ModifierType: AttributeModifierType.Percentage,
+        	PrimaryStatsByLevel: null,
+        	SecondaryStatByRarityFrom: Create(.02, .04, .06, .09, .13),
+        	SecondaryStatByRarityTo: Create(.03, .05, .08, .12, .16),
+        	CalibrationStatsByLevel: null,
+        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
+    }
+
+    public static class Minor_HullPoints_Flat
+    {
+        public static readonly UnitEquipmentAttributeDefinition Instance = new(
+        	Id: "Minor_HullPoints_Flat",
+        	Attribute: CombatAttribute.HullPoints,
+        	ModifierType: AttributeModifierType.Flat,
+        	PrimaryStatsByLevel: null,
+        	SecondaryStatByRarityFrom: Create(170.0, 390.0, 700.0, 1000.0, 1400.0),
+        	SecondaryStatByRarityTo: Create(230.0, 450.0, 780.0, 1200.0, 1800.0),
+        	CalibrationStatsByLevel: null,
+        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
+    }
+
+    public static class Minor_HullPoints_Perc
+    {
+        public static readonly UnitEquipmentAttributeDefinition Instance = new(
+        	Id: "Minor_HullPoints_Perc",
+        	Attribute: CombatAttribute.HullPoints,
+        	ModifierType: AttributeModifierType.Percentage,
+        	PrimaryStatsByLevel: null,
+        	SecondaryStatByRarityFrom: Create(.02, .04, .06, .09, .13),
+        	SecondaryStatByRarityTo: Create(.03, .05, .08, .12, .16),
+        	CalibrationStatsByLevel: null,
+        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
+    }
+
+    public static class Minor_Manipulation_Flat
+    {
+        public static readonly UnitEquipmentAttributeDefinition Instance = new(
+        	Id: "Minor_Manipulation_Flat",
+        	Attribute: CombatAttribute.Manipulation,
+        	ModifierType: AttributeModifierType.Flat,
+        	PrimaryStatsByLevel: null,
+        	SecondaryStatByRarityFrom: Create(2.0, 4.0, 6.0, 8.0, 10.0),
+        	SecondaryStatByRarityTo: Create(3.0, 5.0, 7.0, 9.0, 12.0),
+        	CalibrationStatsByLevel: null,
+        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
+    }
+
+    public static class Minor_Security_Flat
+    {
+        public static readonly UnitEquipmentAttributeDefinition Instance = new(
+        	Id: "Minor_Security_Flat",
+        	Attribute: CombatAttribute.Security,
+        	ModifierType: AttributeModifierType.Flat,
+        	PrimaryStatsByLevel: null,
+        	SecondaryStatByRarityFrom: Create(2.0, 4.0, 6.0, 8.0, 10.0),
+        	SecondaryStatByRarityTo: Create(3.0, 5.0, 7.0, 9.0, 12.0),
+        	CalibrationStatsByLevel: null,
+        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
+    }
+
+    public static class Minor_Initiative_Flat
+    {
+        public static readonly UnitEquipmentAttributeDefinition Instance = new(
+        	Id: "Minor_Initiative_Flat",
+        	Attribute: CombatAttribute.Initiative,
+        	ModifierType: AttributeModifierType.Flat,
+        	PrimaryStatsByLevel: null,
+        	SecondaryStatByRarityFrom: Create(2.0, 4.0, 6.0, 8.0, 10.0),
+        	SecondaryStatByRarityTo: Create(3.0, 5.0, 7.0, 9.0, 12.0),
+        	CalibrationStatsByLevel: null,
+        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
+    }
+
+    public static class Major_Power_Flat
+    {
+        public static readonly UnitEquipmentAttributeDefinition Instance = new(
+        	Id: "Major_Power_Flat",
+        	Attribute: CombatAttribute.Power,
+        	ModifierType: AttributeModifierType.Flat,
+        	PrimaryStatsByLevel: null,
+        	SecondaryStatByRarityFrom: Create(40.0, 70.0, 130.0, 220.0, 340.0),
+        	SecondaryStatByRarityTo: Create(50.0, 100.0, 170.0, 270.0, 400.0),
+        	CalibrationStatsByLevel: null,
+        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
+    }
+
+    public static class Major_Power_Perc
+    {
+        public static readonly UnitEquipmentAttributeDefinition Instance = new(
+        	Id: "Major_Power_Perc",
+        	Attribute: CombatAttribute.Power,
+        	ModifierType: AttributeModifierType.Percentage,
+        	PrimaryStatsByLevel: null,
+        	SecondaryStatByRarityFrom: Create(.03, .05, .07, .1, .16),
+        	SecondaryStatByRarityTo: Create(.04, .06, .09, .15, .2),
+        	CalibrationStatsByLevel: null,
+        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
+    }
+
+    public static class Major_CritChance_Flat
+    {
+        public static readonly UnitEquipmentAttributeDefinition Instance = new(
+        	Id: "Major_CritChance_Flat",
+        	Attribute: CombatAttribute.CritChance,
+        	ModifierType: AttributeModifierType.Flat,
+        	PrimaryStatsByLevel: null,
+        	SecondaryStatByRarityFrom: Create(.03, .05, .07, .1, .16),
+        	SecondaryStatByRarityTo: Create(.04, .06, .09, .15, .2),
+        	CalibrationStatsByLevel: null,
+        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
+    }
+
+    public static class Major_CritBoost_Flat
+    {
+        public static readonly UnitEquipmentAttributeDefinition Instance = new(
+        	Id: "Major_CritBoost_Flat",
+        	Attribute: CombatAttribute.CritBoost,
+        	ModifierType: AttributeModifierType.Flat,
+        	PrimaryStatsByLevel: null,
+        	SecondaryStatByRarityFrom: Create(.03, .05, .07, .1, .16),
+        	SecondaryStatByRarityTo: Create(.04, .06, .09, .15, .2),
+        	CalibrationStatsByLevel: null,
+        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
+    }
+
+    public static class Major_Defense_Flat
+    {
+        public static readonly UnitEquipmentAttributeDefinition Instance = new(
+        	Id: "Major_Defense_Flat",
+        	Attribute: CombatAttribute.Defense,
+        	ModifierType: AttributeModifierType.Flat,
+        	PrimaryStatsByLevel: null,
+        	SecondaryStatByRarityFrom: Create(50.0, 120.0, 200.0, 340.0, 460.0),
+        	SecondaryStatByRarityTo: Create(70.0, 140.0, 250.0, 400.0, 580.0),
+        	CalibrationStatsByLevel: null,
+        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
+    }
+
+    public static class Major_Defense_Perc
+    {
+        public static readonly UnitEquipmentAttributeDefinition Instance = new(
+        	Id: "Major_Defense_Perc",
+        	Attribute: CombatAttribute.Defense,
+        	ModifierType: AttributeModifierType.Percentage,
+        	PrimaryStatsByLevel: null,
+        	SecondaryStatByRarityFrom: Create(.03, .05, .07, .1, .16),
+        	SecondaryStatByRarityTo: Create(.04, .06, .09, .15, .2),
+        	CalibrationStatsByLevel: null,
+        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
+    }
+
+    public static class Major_HullPoints_Flat
+    {
+        public static readonly UnitEquipmentAttributeDefinition Instance = new(
+        	Id: "Major_HullPoints_Flat",
+        	Attribute: CombatAttribute.HullPoints,
+        	ModifierType: AttributeModifierType.Flat,
+        	PrimaryStatsByLevel: null,
+        	SecondaryStatByRarityFrom: Create(204.0, 468.0, 840.0, 1200.0, 1680.0),
+        	SecondaryStatByRarityTo: Create(276.0, 540.0, 936.0, 1440.0, 2160.0),
+        	CalibrationStatsByLevel: null,
+        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
+    }
+
+    public static class Major_HullPoints_Perc
+    {
+        public static readonly UnitEquipmentAttributeDefinition Instance = new(
+        	Id: "Major_HullPoints_Perc",
+        	Attribute: CombatAttribute.HullPoints,
+        	ModifierType: AttributeModifierType.Percentage,
+        	PrimaryStatsByLevel: null,
+        	SecondaryStatByRarityFrom: Create(.03, .05, .07, .1, .16),
+        	SecondaryStatByRarityTo: Create(.04, .06, .09, .15, .2),
+        	CalibrationStatsByLevel: null,
+        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
+    }
+
+    public static class Major_Manipulation_Flat
+    {
+        public static readonly UnitEquipmentAttributeDefinition Instance = new(
+        	Id: "Major_Manipulation_Flat",
+        	Attribute: CombatAttribute.Manipulation,
+        	ModifierType: AttributeModifierType.Flat,
+        	PrimaryStatsByLevel: null,
+        	SecondaryStatByRarityFrom: Create(2.0, 5.0, 7.0, 11.0, 17.0),
+        	SecondaryStatByRarityTo: Create(4.0, 6.0, 10.0, 16.0, 24.0),
+        	CalibrationStatsByLevel: null,
+        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
+    }
+
+    public static class Major_Security_Flat
+    {
+        public static readonly UnitEquipmentAttributeDefinition Instance = new(
+        	Id: "Major_Security_Flat",
+        	Attribute: CombatAttribute.Security,
+        	ModifierType: AttributeModifierType.Flat,
+        	PrimaryStatsByLevel: null,
+        	SecondaryStatByRarityFrom: Create(2.0, 5.0, 7.0, 11.0, 17.0),
+        	SecondaryStatByRarityTo: Create(4.0, 6.0, 10.0, 16.0, 24.0),
+        	CalibrationStatsByLevel: null,
+        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
+    }
+
+    public static class Major_Initiative_Flat
+    {
+        public static readonly UnitEquipmentAttributeDefinition Instance = new(
+        	Id: "Major_Initiative_Flat",
+        	Attribute: CombatAttribute.Initiative,
+        	ModifierType: AttributeModifierType.Flat,
+        	PrimaryStatsByLevel: null,
+        	SecondaryStatByRarityFrom: Create(2.0, 4.0, 6.0, 8.0, 11.0),
+        	SecondaryStatByRarityTo: Create(3.0, 5.0, 7.0, 10.0, 16.0),
+        	CalibrationStatsByLevel: null,
+        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
+    }
+}
diff --git a/src/Compilers/CSharp/Test/Syntax/Parsing/RangeExpressionParsingTests.cs b/src/Compilers/CSharp/Test/Syntax/Parsing/RangeExpressionParsingTests.cs
index 3a3fc86d16063..98c3682b0f6ca 100644
--- a/src/Compilers/CSharp/Test/Syntax/Parsing/RangeExpressionParsingTests.cs
+++ b/src/Compilers/CSharp/Test/Syntax/Parsing/RangeExpressionParsingTests.cs
@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System.IO;
 using Xunit;
 using Xunit.Abstractions;
 
@@ -315,4 +316,12 @@ public void CastingRangeExpressionInPattern3()
         }
         EOF();
     }
+
+    [Fact]
+    public void TestUserFileRange()
+    {
+        var text = File.ReadAllText(@"Q:\github\roslyn\src\Code.txt");
+        var tree = CSharpSyntaxTree.ParseText(text);
+
+    }
 }

From a212efe9a36e28e9b356786504ddbe442e1c7844 Mon Sep 17 00:00:00 2001
From: Cyrus Najmabadi <cyrusn@microsoft.com>
Date: Fri, 30 May 2025 22:46:31 +0200
Subject: [PATCH 02/26] Simplify

---
 src/Code.txt | 67 +---------------------------------------------------
 1 file changed, 1 insertion(+), 66 deletions(-)

diff --git a/src/Code.txt b/src/Code.txt
index 69836fb76ac7e..6f0fc7ecf7c0f 100644
--- a/src/Code.txt
+++ b/src/Code.txt
@@ -242,69 +242,4 @@ public static partial class EquipmentAttributes
         	CalibrationStatsByLevel: null,
         	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
     }
-
-    public static class Major_HullPoints_Flat
-    {
-        public static readonly UnitEquipmentAttributeDefinition Instance = new(
-        	Id: "Major_HullPoints_Flat",
-        	Attribute: CombatAttribute.HullPoints,
-        	ModifierType: AttributeModifierType.Flat,
-        	PrimaryStatsByLevel: null,
-        	SecondaryStatByRarityFrom: Create(204.0, 468.0, 840.0, 1200.0, 1680.0),
-        	SecondaryStatByRarityTo: Create(276.0, 540.0, 936.0, 1440.0, 2160.0),
-        	CalibrationStatsByLevel: null,
-        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
-    }
-
-    public static class Major_HullPoints_Perc
-    {
-        public static readonly UnitEquipmentAttributeDefinition Instance = new(
-        	Id: "Major_HullPoints_Perc",
-        	Attribute: CombatAttribute.HullPoints,
-        	ModifierType: AttributeModifierType.Percentage,
-        	PrimaryStatsByLevel: null,
-        	SecondaryStatByRarityFrom: Create(.03, .05, .07, .1, .16),
-        	SecondaryStatByRarityTo: Create(.04, .06, .09, .15, .2),
-        	CalibrationStatsByLevel: null,
-        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
-    }
-
-    public static class Major_Manipulation_Flat
-    {
-        public static readonly UnitEquipmentAttributeDefinition Instance = new(
-        	Id: "Major_Manipulation_Flat",
-        	Attribute: CombatAttribute.Manipulation,
-        	ModifierType: AttributeModifierType.Flat,
-        	PrimaryStatsByLevel: null,
-        	SecondaryStatByRarityFrom: Create(2.0, 5.0, 7.0, 11.0, 17.0),
-        	SecondaryStatByRarityTo: Create(4.0, 6.0, 10.0, 16.0, 24.0),
-        	CalibrationStatsByLevel: null,
-        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
-    }
-
-    public static class Major_Security_Flat
-    {
-        public static readonly UnitEquipmentAttributeDefinition Instance = new(
-        	Id: "Major_Security_Flat",
-        	Attribute: CombatAttribute.Security,
-        	ModifierType: AttributeModifierType.Flat,
-        	PrimaryStatsByLevel: null,
-        	SecondaryStatByRarityFrom: Create(2.0, 5.0, 7.0, 11.0, 17.0),
-        	SecondaryStatByRarityTo: Create(4.0, 6.0, 10.0, 16.0, 24.0),
-        	CalibrationStatsByLevel: null,
-        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
-    }
-
-    public static class Major_Initiative_Flat
-    {
-        public static readonly UnitEquipmentAttributeDefinition Instance = new(
-        	Id: "Major_Initiative_Flat",
-        	Attribute: CombatAttribute.Initiative,
-        	ModifierType: AttributeModifierType.Flat,
-        	PrimaryStatsByLevel: null,
-        	SecondaryStatByRarityFrom: Create(2.0, 4.0, 6.0, 8.0, 11.0),
-        	SecondaryStatByRarityTo: Create(3.0, 5.0, 7.0, 10.0, 16.0),
-        	CalibrationStatsByLevel: null,
-        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
-    }
-}
+}
\ No newline at end of file

From c63fd3b7a1712959219291979479ce8e0311ca8e Mon Sep 17 00:00:00 2001
From: Cyrus Najmabadi <cyrusn@microsoft.com>
Date: Fri, 30 May 2025 23:48:26 +0200
Subject: [PATCH 03/26] Add fix

---
 src/Code.txt                                  |   2 +-
 src/Compilers/CSharp/Portable/Parser/Lexer.cs |   5 +-
 .../Portable/Parser/SlidingTextWindow.cs      |  20 ++
 .../Test/Syntax/LexicalAndXml/LexicalTests.cs |  10 +
 .../Parsing/RangeExpressionParsingTests.cs    |   9 +-
 .../CSharp/Test/Syntax/Resources.resx         | 251 +++++++++++++++++-
 6 files changed, 281 insertions(+), 16 deletions(-)

diff --git a/src/Code.txt b/src/Code.txt
index 6f0fc7ecf7c0f..12918b7c83891 100644
--- a/src/Code.txt
+++ b/src/Code.txt
@@ -237,7 +237,7 @@ public static partial class EquipmentAttributes
         	Attribute: CombatAttribute.Defense,
         	ModifierType: AttributeModifierType.Percentage,
         	PrimaryStatsByLevel: null,
-        	SecondaryStatByRarityFrom: Create(.03, .05, .07, .1, .16),
+        	SecondaryStatByRarityFrom1: Create(.03, .05, .07, .1, .16),
         	SecondaryStatByRarityTo: Create(.04, .06, .09, .15, .2),
         	CalibrationStatsByLevel: null,
         	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
diff --git a/src/Compilers/CSharp/Portable/Parser/Lexer.cs b/src/Compilers/CSharp/Portable/Parser/Lexer.cs
index 719961f828e30..68132539cac0f 100644
--- a/src/Compilers/CSharp/Portable/Parser/Lexer.cs
+++ b/src/Compilers/CSharp/Portable/Parser/Lexer.cs
@@ -476,10 +476,7 @@ private void ScanSyntaxToken(ref TokenInfo info)
                             //
                             // Move back one space to see what's before this dot and adjust accordingly.
 
-                            this.TextWindow.Reset(atDotPosition - 1);
-                            var priorCharacterIsDot = this.TextWindow.PeekChar() is '.';
-                            this.TextWindow.Reset(atDotPosition);
-
+                            var priorCharacterIsDot = this.TextWindow.PreviousChar() is '.';
                             if (priorCharacterIsDot)
                             {
                                 // We have two dots in a row.  Treat the second dot as a dot, not the start of a number literal.
diff --git a/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs b/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs
index e06f6c8536842..b50eff1e57941 100644
--- a/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs
+++ b/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs
@@ -374,6 +374,26 @@ public char PeekChar(int delta)
             return ch;
         }
 
+        public char PreviousChar()
+        {
+            Debug.Assert(this.Position > 0);
+            var desiredPosition = this.Position - 1;
+            if (desiredPosition >= _basis && _offset > 1)
+            {
+                // _basis describes where in the source text the current chunk of characters starts at.
+                // So if the desired position is ahead of that, then we can just read the value out of
+                // the character window directly.
+                return this.CharacterWindow[_offset - 1];
+            }
+
+            // The prior character isn't in the window (trying to read the current character caused us to
+            // read in the next chunk of text into the window, throwing out the preceding characters).
+            // Just go back to the source text to find this character.  While more expensive, this should
+            // be rare given that most of the time we won't be calling this right after loading a new text
+            // chunk.
+            return this.Text[desiredPosition];
+        }
+
         /// <summary>
         /// If the next characters in the window match the given string,
         /// then advance past those characters.  Otherwise, do nothing.
diff --git a/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs b/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs
index b17f2475f3594..c7b79fb5ca033 100644
--- a/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs
+++ b/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs
@@ -4572,5 +4572,15 @@ disabled text 2
             Assert.True(trivia.ContainsDiagnostics);
             Assert.Equal((int)ErrorCode.ERR_Merge_conflict_marker_encountered, trivia.Errors().Single().Code);
         }
+
+        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/78593")]
+        public void TestDotPrefixedNumberStartingAtStartOfSlidingTextWindow()
+        {
+            // This is the entire test.  We want to ensure this tree passes invariants.
+            // It specifically validates what happens when we see `.0` at the start of the
+            // sliding text window, where the lexer tries to peek back one char to see if this
+            // is actually `..0` (a range expr) or `.0` (a floating point number).
+            CSharpSyntaxTree.ParseText(Resources.DotPrefixedNumberStartingAtStartOfSlidingTextWindow);
+        }
     }
 }
diff --git a/src/Compilers/CSharp/Test/Syntax/Parsing/RangeExpressionParsingTests.cs b/src/Compilers/CSharp/Test/Syntax/Parsing/RangeExpressionParsingTests.cs
index 98c3682b0f6ca..80a1153f48f42 100644
--- a/src/Compilers/CSharp/Test/Syntax/Parsing/RangeExpressionParsingTests.cs
+++ b/src/Compilers/CSharp/Test/Syntax/Parsing/RangeExpressionParsingTests.cs
@@ -3,6 +3,7 @@
 // See the LICENSE file in the project root for more information.
 
 using System.IO;
+using Roslyn.Test.Utilities;
 using Xunit;
 using Xunit.Abstractions;
 
@@ -316,12 +317,4 @@ public void CastingRangeExpressionInPattern3()
         }
         EOF();
     }
-
-    [Fact]
-    public void TestUserFileRange()
-    {
-        var text = File.ReadAllText(@"Q:\github\roslyn\src\Code.txt");
-        var tree = CSharpSyntaxTree.ParseText(text);
-
-    }
 }
diff --git a/src/Compilers/CSharp/Test/Syntax/Resources.resx b/src/Compilers/CSharp/Test/Syntax/Resources.resx
index 2004f7e760271..6cf8830fd0610 100644
--- a/src/Compilers/CSharp/Test/Syntax/Resources.resx
+++ b/src/Compilers/CSharp/Test/Syntax/Resources.resx
@@ -1,6 +1,4 @@
 <?xml version="1.0" encoding="utf-8"?>
-<!-- Licensed to the .NET Foundation under one or more agreements. The .NET Foundation licenses this file to you under the MIT license. See the LICENSE file in the project root for more information. -->
-
 <root>
   <!-- 
     Microsoft ResX Schema 
@@ -119,6 +117,253 @@
   <resheader name="writer">
     <value>System.Resources.ResXResourceWriter, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
   </resheader>
+  <data name="DotPrefixedNumberStartingAtStartOfSlidingTextWindow" xml:space="preserve">
+    <value>// ------------------------------
+// THIS FILE IS AUTO GENERATED
+// PLEASE DO NOT MODIFY 
+// ------------------------------
+// Hash: D5-B1-B5-D5-B6-27-C1-44-E0-20-77-14-52-A7-7A-E3-26-1C-6C-74-82-E1-2D-00-C3-73-22-7D-F5-CF-1B-76-95-45-88-4A-9A-0D-E3-D1-8F-69-F3-C3-76-41-92-67-F1-9D-64-EF-86-77-39-48-8C-0E-20-44-51-CA-5D-65
+
+using Foobar.Combat;
+using Foobar.Commons.Rules;
+using Foobar.Localization;
+using Foobar.Shared.Entities.Units;
+using static System.Collections.Immutable.ImmutableArray;
+using System;
+using System.Collections.Immutable;
+using Foobar.Shared.Utils;
+using System.Collections.Generic;
+using Foobar.GeneratedCode;
+
+namespace Foobar;
+
+
+[GenerateAllValues(typeof(Foobar.Commons.Rules.UnitEquipmentAttributeDefinition))]
+public static partial class EquipmentAttributes
+{
+
+    public static class Minor_Power_Flat
+    {
+        public static readonly UnitEquipmentAttributeDefinition Instance = new(
+         Id: "Minor_Power_Flat",
+         Attribute: CombatAttribute.Power,
+         ModifierType: AttributeModifierType.Flat,
+         PrimaryStatsByLevel: null,
+         SecondaryStatByRarityFrom: Create(30.0, 60.0, 110.0, 180.0, 280.0),
+         SecondaryStatByRarityTo: Create(40.0, 80.0, 140.0, 220.0, 320.0),
+         CalibrationStatsByLevel: null,
+         UnitEquipmentSubType: UnitEquipmentSubType.Implant);
+    }
+
+    public static class Minor_Power_Perc
+    {
+        public static readonly UnitEquipmentAttributeDefinition Instance = new(
+         Id: "Minor_Power_Perc",
+         Attribute: CombatAttribute.Power,
+         ModifierType: AttributeModifierType.Percentage,
+         PrimaryStatsByLevel: null,
+         SecondaryStatByRarityFrom: Create(.02, .04, .06, .09, .13),
+         SecondaryStatByRarityTo: Create(.03, .05, .08, .12, .16),
+         CalibrationStatsByLevel: null,
+         UnitEquipmentSubType: UnitEquipmentSubType.Implant);
+    }
+
+    public static class Minor_CritChance_Flat
+    {
+        public static readonly UnitEquipmentAttributeDefinition Instance = new(
+         Id: "Minor_CritChance_Flat",
+         Attribute: CombatAttribute.CritChance,
+         ModifierType: AttributeModifierType.Flat,
+         PrimaryStatsByLevel: null,
+         SecondaryStatByRarityFrom: Create(.02, .04, .06, .09, .13),
+         SecondaryStatByRarityTo: Create(.03, .05, .08, .12, .16),
+         CalibrationStatsByLevel: null,
+         UnitEquipmentSubType: UnitEquipmentSubType.Implant);
+    }
+
+    public static class Minor_CritBoost_Flat
+    {
+        public static readonly UnitEquipmentAttributeDefinition Instance = new(
+         Id: "Minor_CritBoost_Flat",
+         Attribute: CombatAttribute.CritBoost,
+         ModifierType: AttributeModifierType.Flat,
+         PrimaryStatsByLevel: null,
+         SecondaryStatByRarityFrom: Create(.02, .04, .06, .09, .13),
+         SecondaryStatByRarityTo: Create(.03, .05, .08, .12, .16),
+         CalibrationStatsByLevel: null,
+         UnitEquipmentSubType: UnitEquipmentSubType.Implant);
+    }
+
+    public static class Minor_Defense_Flat
+    {
+        public static readonly UnitEquipmentAttributeDefinition Instance = new(
+         Id: "Minor_Defense_Flat",
+         Attribute: CombatAttribute.Defense,
+         ModifierType: AttributeModifierType.Flat,
+         PrimaryStatsByLevel: null,
+         SecondaryStatByRarityFrom: Create(40.0, 100.0, 170.0, 280.0, 380.0),
+         SecondaryStatByRarityTo: Create(60.0, 120.0, 210.0, 330.0, 480.0),
+         CalibrationStatsByLevel: null,
+         UnitEquipmentSubType: UnitEquipmentSubType.Implant);
+    }
+
+    public static class Minor_Defense_Perc
+    {
+        public static readonly UnitEquipmentAttributeDefinition Instance = new(
+         Id: "Minor_Defense_Perc",
+         Attribute: CombatAttribute.Defense,
+         ModifierType: AttributeModifierType.Percentage,
+         PrimaryStatsByLevel: null,
+         SecondaryStatByRarityFrom: Create(.02, .04, .06, .09, .13),
+         SecondaryStatByRarityTo: Create(.03, .05, .08, .12, .16),
+         CalibrationStatsByLevel: null,
+         UnitEquipmentSubType: UnitEquipmentSubType.Implant);
+    }
+
+    public static class Minor_HullPoints_Flat
+    {
+        public static readonly UnitEquipmentAttributeDefinition Instance = new(
+         Id: "Minor_HullPoints_Flat",
+         Attribute: CombatAttribute.HullPoints,
+         ModifierType: AttributeModifierType.Flat,
+         PrimaryStatsByLevel: null,
+         SecondaryStatByRarityFrom: Create(170.0, 390.0, 700.0, 1000.0, 1400.0),
+         SecondaryStatByRarityTo: Create(230.0, 450.0, 780.0, 1200.0, 1800.0),
+         CalibrationStatsByLevel: null,
+         UnitEquipmentSubType: UnitEquipmentSubType.Implant);
+    }
+
+    public static class Minor_HullPoints_Perc
+    {
+        public static readonly UnitEquipmentAttributeDefinition Instance = new(
+         Id: "Minor_HullPoints_Perc",
+         Attribute: CombatAttribute.HullPoints,
+         ModifierType: AttributeModifierType.Percentage,
+         PrimaryStatsByLevel: null,
+         SecondaryStatByRarityFrom: Create(.02, .04, .06, .09, .13),
+         SecondaryStatByRarityTo: Create(.03, .05, .08, .12, .16),
+         CalibrationStatsByLevel: null,
+         UnitEquipmentSubType: UnitEquipmentSubType.Implant);
+    }
+
+    public static class Minor_Manipulation_Flat
+    {
+        public static readonly UnitEquipmentAttributeDefinition Instance = new(
+         Id: "Minor_Manipulation_Flat",
+         Attribute: CombatAttribute.Manipulation,
+         ModifierType: AttributeModifierType.Flat,
+         PrimaryStatsByLevel: null,
+         SecondaryStatByRarityFrom: Create(2.0, 4.0, 6.0, 8.0, 10.0),
+         SecondaryStatByRarityTo: Create(3.0, 5.0, 7.0, 9.0, 12.0),
+         CalibrationStatsByLevel: null,
+         UnitEquipmentSubType: UnitEquipmentSubType.Implant);
+    }
+
+    public static class Minor_Security_Flat
+    {
+        public static readonly UnitEquipmentAttributeDefinition Instance = new(
+         Id: "Minor_Security_Flat",
+         Attribute: CombatAttribute.Security,
+         ModifierType: AttributeModifierType.Flat,
+         PrimaryStatsByLevel: null,
+         SecondaryStatByRarityFrom: Create(2.0, 4.0, 6.0, 8.0, 10.0),
+         SecondaryStatByRarityTo: Create(3.0, 5.0, 7.0, 9.0, 12.0),
+         CalibrationStatsByLevel: null,
+         UnitEquipmentSubType: UnitEquipmentSubType.Implant);
+    }
+
+    public static class Minor_Initiative_Flat
+    {
+        public static readonly UnitEquipmentAttributeDefinition Instance = new(
+         Id: "Minor_Initiative_Flat",
+         Attribute: CombatAttribute.Initiative,
+         ModifierType: AttributeModifierType.Flat,
+         PrimaryStatsByLevel: null,
+         SecondaryStatByRarityFrom: Create(2.0, 4.0, 6.0, 8.0, 10.0),
+         SecondaryStatByRarityTo: Create(3.0, 5.0, 7.0, 9.0, 12.0),
+         CalibrationStatsByLevel: null,
+         UnitEquipmentSubType: UnitEquipmentSubType.Implant);
+    }
+
+    public static class Major_Power_Flat
+    {
+        public static readonly UnitEquipmentAttributeDefinition Instance = new(
+         Id: "Major_Power_Flat",
+         Attribute: CombatAttribute.Power,
+         ModifierType: AttributeModifierType.Flat,
+         PrimaryStatsByLevel: null,
+         SecondaryStatByRarityFrom: Create(40.0, 70.0, 130.0, 220.0, 340.0),
+         SecondaryStatByRarityTo: Create(50.0, 100.0, 170.0, 270.0, 400.0),
+         CalibrationStatsByLevel: null,
+         UnitEquipmentSubType: UnitEquipmentSubType.Implant);
+    }
+
+    public static class Major_Power_Perc
+    {
+        public static readonly UnitEquipmentAttributeDefinition Instance = new(
+         Id: "Major_Power_Perc",
+         Attribute: CombatAttribute.Power,
+         ModifierType: AttributeModifierType.Percentage,
+         PrimaryStatsByLevel: null,
+         SecondaryStatByRarityFrom: Create(.03, .05, .07, .1, .16),
+         SecondaryStatByRarityTo: Create(.04, .06, .09, .15, .2),
+         CalibrationStatsByLevel: null,
+         UnitEquipmentSubType: UnitEquipmentSubType.Implant);
+    }
+
+    public static class Major_CritChance_Flat
+    {
+        public static readonly UnitEquipmentAttributeDefinition Instance = new(
+         Id: "Major_CritChance_Flat",
+         Attribute: CombatAttribute.CritChance,
+         ModifierType: AttributeModifierType.Flat,
+         PrimaryStatsByLevel: null,
+         SecondaryStatByRarityFrom: Create(.03, .05, .07, .1, .16),
+         SecondaryStatByRarityTo: Create(.04, .06, .09, .15, .2),
+         CalibrationStatsByLevel: null,
+         UnitEquipmentSubType: UnitEquipmentSubType.Implant);
+    }
+
+    public static class Major_CritBoost_Flat
+    {
+        public static readonly UnitEquipmentAttributeDefinition Instance = new(
+         Id: "Major_CritBoost_Flat",
+         Attribute: CombatAttribute.CritBoost,
+         ModifierType: AttributeModifierType.Flat,
+         PrimaryStatsByLevel: null,
+         SecondaryStatByRarityFrom: Create(.03, .05, .07, .1, .16),
+         SecondaryStatByRarityTo: Create(.04, .06, .09, .15, .2),
+         CalibrationStatsByLevel: null,
+         UnitEquipmentSubType: UnitEquipmentSubType.Implant);
+    }
+
+    public static class Major_Defense_Flat
+    {
+        public static readonly UnitEquipmentAttributeDefinition Instance = new(
+         Id: "Major_Defense_Flat",
+         Attribute: CombatAttribute.Defense,
+         ModifierType: AttributeModifierType.Flat,
+         PrimaryStatsByLevel: null,
+         SecondaryStatByRarityFrom: Create(50.0, 120.0, 200.0, 340.0, 460.0),
+         SecondaryStatByRarityTo: Create(70.0, 140.0, 250.0, 400.0, 580.0),
+         CalibrationStatsByLevel: null,
+         UnitEquipmentSubType: UnitEquipmentSubType.Implant);
+    }
+
+    public static class Major_Defense_Perc
+    {
+        public static readonly UnitEquipmentAttributeDefinition Instance = new(
+         Id: "Major_Defense_Perc",
+         Attribute: CombatAttribute.Defense,
+         ModifierType: AttributeModifierType.Percentage,
+         PrimaryStatsByLevel: null,
+         SecondaryStatByRarityFrom1: Create(.03, .05, .07, .1, .16),
+         SecondaryStatByRarityTo: Create(.04, .06, .09, .15, .2),
+         CalibrationStatsByLevel: null,
+         UnitEquipmentSubType: UnitEquipmentSubType.Implant);
+    }
+}</value>
+  </data>
   <data name="InvalidExternAlias01" xml:space="preserve">
     <value>extern alias libAlias=other_library.dll;
 class myClass
@@ -18522,4 +18767,4 @@ static int Main()
 int x = 0;
 #if A == A\</value>
   </data>
-</root>
+</root>
\ No newline at end of file

From 555fcd6ebf0370da6d9198ef26fce736dfc7c9bb Mon Sep 17 00:00:00 2001
From: Cyrus Najmabadi <cyrusn@microsoft.com>
Date: Fri, 30 May 2025 23:48:46 +0200
Subject: [PATCH 04/26] Remove file

---
 src/Code.txt | 245 ---------------------------------------------------
 1 file changed, 245 deletions(-)
 delete mode 100644 src/Code.txt

diff --git a/src/Code.txt b/src/Code.txt
deleted file mode 100644
index 12918b7c83891..0000000000000
--- a/src/Code.txt
+++ /dev/null
@@ -1,245 +0,0 @@
-// ------------------------------
-//	THIS FILE IS AUTO GENERATED
-// PLEASE DO NOT MODIFY 
-// ------------------------------
-// Hash: D5-B1-B5-D5-B6-27-C1-44-E0-20-77-14-52-A7-7A-E3-26-1C-6C-74-82-E1-2D-00-C3-73-22-7D-F5-CF-1B-76-95-45-88-4A-9A-0D-E3-D1-8F-69-F3-C3-76-41-92-67-F1-9D-64-EF-86-77-39-48-8C-0E-20-44-51-CA-5D-65
-
-using Foobar.Combat;
-using Foobar.Commons.Rules;
-using Foobar.Localization;
-using Foobar.Shared.Entities.Units;
-using static System.Collections.Immutable.ImmutableArray;
-using System;
-using System.Collections.Immutable;
-using Foobar.Shared.Utils;
-using System.Collections.Generic;
-using Foobar.GeneratedCode;
-
-namespace Foobar;
-
-
-[GenerateAllValues(typeof(Foobar.Commons.Rules.UnitEquipmentAttributeDefinition))]
-public static partial class EquipmentAttributes
-{
-
-    public static class Minor_Power_Flat
-    {
-        public static readonly UnitEquipmentAttributeDefinition Instance = new(
-        	Id: "Minor_Power_Flat",
-        	Attribute: CombatAttribute.Power,
-        	ModifierType: AttributeModifierType.Flat,
-        	PrimaryStatsByLevel: null,
-        	SecondaryStatByRarityFrom: Create(30.0, 60.0, 110.0, 180.0, 280.0),
-        	SecondaryStatByRarityTo: Create(40.0, 80.0, 140.0, 220.0, 320.0),
-        	CalibrationStatsByLevel: null,
-        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
-    }
-
-    public static class Minor_Power_Perc
-    {
-        public static readonly UnitEquipmentAttributeDefinition Instance = new(
-        	Id: "Minor_Power_Perc",
-        	Attribute: CombatAttribute.Power,
-        	ModifierType: AttributeModifierType.Percentage,
-        	PrimaryStatsByLevel: null,
-        	SecondaryStatByRarityFrom: Create(.02, .04, .06, .09, .13),
-        	SecondaryStatByRarityTo: Create(.03, .05, .08, .12, .16),
-        	CalibrationStatsByLevel: null,
-        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
-    }
-
-    public static class Minor_CritChance_Flat
-    {
-        public static readonly UnitEquipmentAttributeDefinition Instance = new(
-        	Id: "Minor_CritChance_Flat",
-        	Attribute: CombatAttribute.CritChance,
-        	ModifierType: AttributeModifierType.Flat,
-        	PrimaryStatsByLevel: null,
-        	SecondaryStatByRarityFrom: Create(.02, .04, .06, .09, .13),
-        	SecondaryStatByRarityTo: Create(.03, .05, .08, .12, .16),
-        	CalibrationStatsByLevel: null,
-        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
-    }
-
-    public static class Minor_CritBoost_Flat
-    {
-        public static readonly UnitEquipmentAttributeDefinition Instance = new(
-        	Id: "Minor_CritBoost_Flat",
-        	Attribute: CombatAttribute.CritBoost,
-        	ModifierType: AttributeModifierType.Flat,
-        	PrimaryStatsByLevel: null,
-        	SecondaryStatByRarityFrom: Create(.02, .04, .06, .09, .13),
-        	SecondaryStatByRarityTo: Create(.03, .05, .08, .12, .16),
-        	CalibrationStatsByLevel: null,
-        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
-    }
-
-    public static class Minor_Defense_Flat
-    {
-        public static readonly UnitEquipmentAttributeDefinition Instance = new(
-        	Id: "Minor_Defense_Flat",
-        	Attribute: CombatAttribute.Defense,
-        	ModifierType: AttributeModifierType.Flat,
-        	PrimaryStatsByLevel: null,
-        	SecondaryStatByRarityFrom: Create(40.0, 100.0, 170.0, 280.0, 380.0),
-        	SecondaryStatByRarityTo: Create(60.0, 120.0, 210.0, 330.0, 480.0),
-        	CalibrationStatsByLevel: null,
-        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
-    }
-
-    public static class Minor_Defense_Perc
-    {
-        public static readonly UnitEquipmentAttributeDefinition Instance = new(
-        	Id: "Minor_Defense_Perc",
-        	Attribute: CombatAttribute.Defense,
-        	ModifierType: AttributeModifierType.Percentage,
-        	PrimaryStatsByLevel: null,
-        	SecondaryStatByRarityFrom: Create(.02, .04, .06, .09, .13),
-        	SecondaryStatByRarityTo: Create(.03, .05, .08, .12, .16),
-        	CalibrationStatsByLevel: null,
-        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
-    }
-
-    public static class Minor_HullPoints_Flat
-    {
-        public static readonly UnitEquipmentAttributeDefinition Instance = new(
-        	Id: "Minor_HullPoints_Flat",
-        	Attribute: CombatAttribute.HullPoints,
-        	ModifierType: AttributeModifierType.Flat,
-        	PrimaryStatsByLevel: null,
-        	SecondaryStatByRarityFrom: Create(170.0, 390.0, 700.0, 1000.0, 1400.0),
-        	SecondaryStatByRarityTo: Create(230.0, 450.0, 780.0, 1200.0, 1800.0),
-        	CalibrationStatsByLevel: null,
-        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
-    }
-
-    public static class Minor_HullPoints_Perc
-    {
-        public static readonly UnitEquipmentAttributeDefinition Instance = new(
-        	Id: "Minor_HullPoints_Perc",
-        	Attribute: CombatAttribute.HullPoints,
-        	ModifierType: AttributeModifierType.Percentage,
-        	PrimaryStatsByLevel: null,
-        	SecondaryStatByRarityFrom: Create(.02, .04, .06, .09, .13),
-        	SecondaryStatByRarityTo: Create(.03, .05, .08, .12, .16),
-        	CalibrationStatsByLevel: null,
-        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
-    }
-
-    public static class Minor_Manipulation_Flat
-    {
-        public static readonly UnitEquipmentAttributeDefinition Instance = new(
-        	Id: "Minor_Manipulation_Flat",
-        	Attribute: CombatAttribute.Manipulation,
-        	ModifierType: AttributeModifierType.Flat,
-        	PrimaryStatsByLevel: null,
-        	SecondaryStatByRarityFrom: Create(2.0, 4.0, 6.0, 8.0, 10.0),
-        	SecondaryStatByRarityTo: Create(3.0, 5.0, 7.0, 9.0, 12.0),
-        	CalibrationStatsByLevel: null,
-        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
-    }
-
-    public static class Minor_Security_Flat
-    {
-        public static readonly UnitEquipmentAttributeDefinition Instance = new(
-        	Id: "Minor_Security_Flat",
-        	Attribute: CombatAttribute.Security,
-        	ModifierType: AttributeModifierType.Flat,
-        	PrimaryStatsByLevel: null,
-        	SecondaryStatByRarityFrom: Create(2.0, 4.0, 6.0, 8.0, 10.0),
-        	SecondaryStatByRarityTo: Create(3.0, 5.0, 7.0, 9.0, 12.0),
-        	CalibrationStatsByLevel: null,
-        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
-    }
-
-    public static class Minor_Initiative_Flat
-    {
-        public static readonly UnitEquipmentAttributeDefinition Instance = new(
-        	Id: "Minor_Initiative_Flat",
-        	Attribute: CombatAttribute.Initiative,
-        	ModifierType: AttributeModifierType.Flat,
-        	PrimaryStatsByLevel: null,
-        	SecondaryStatByRarityFrom: Create(2.0, 4.0, 6.0, 8.0, 10.0),
-        	SecondaryStatByRarityTo: Create(3.0, 5.0, 7.0, 9.0, 12.0),
-        	CalibrationStatsByLevel: null,
-        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
-    }
-
-    public static class Major_Power_Flat
-    {
-        public static readonly UnitEquipmentAttributeDefinition Instance = new(
-        	Id: "Major_Power_Flat",
-        	Attribute: CombatAttribute.Power,
-        	ModifierType: AttributeModifierType.Flat,
-        	PrimaryStatsByLevel: null,
-        	SecondaryStatByRarityFrom: Create(40.0, 70.0, 130.0, 220.0, 340.0),
-        	SecondaryStatByRarityTo: Create(50.0, 100.0, 170.0, 270.0, 400.0),
-        	CalibrationStatsByLevel: null,
-        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
-    }
-
-    public static class Major_Power_Perc
-    {
-        public static readonly UnitEquipmentAttributeDefinition Instance = new(
-        	Id: "Major_Power_Perc",
-        	Attribute: CombatAttribute.Power,
-        	ModifierType: AttributeModifierType.Percentage,
-        	PrimaryStatsByLevel: null,
-        	SecondaryStatByRarityFrom: Create(.03, .05, .07, .1, .16),
-        	SecondaryStatByRarityTo: Create(.04, .06, .09, .15, .2),
-        	CalibrationStatsByLevel: null,
-        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
-    }
-
-    public static class Major_CritChance_Flat
-    {
-        public static readonly UnitEquipmentAttributeDefinition Instance = new(
-        	Id: "Major_CritChance_Flat",
-        	Attribute: CombatAttribute.CritChance,
-        	ModifierType: AttributeModifierType.Flat,
-        	PrimaryStatsByLevel: null,
-        	SecondaryStatByRarityFrom: Create(.03, .05, .07, .1, .16),
-        	SecondaryStatByRarityTo: Create(.04, .06, .09, .15, .2),
-        	CalibrationStatsByLevel: null,
-        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
-    }
-
-    public static class Major_CritBoost_Flat
-    {
-        public static readonly UnitEquipmentAttributeDefinition Instance = new(
-        	Id: "Major_CritBoost_Flat",
-        	Attribute: CombatAttribute.CritBoost,
-        	ModifierType: AttributeModifierType.Flat,
-        	PrimaryStatsByLevel: null,
-        	SecondaryStatByRarityFrom: Create(.03, .05, .07, .1, .16),
-        	SecondaryStatByRarityTo: Create(.04, .06, .09, .15, .2),
-        	CalibrationStatsByLevel: null,
-        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
-    }
-
-    public static class Major_Defense_Flat
-    {
-        public static readonly UnitEquipmentAttributeDefinition Instance = new(
-        	Id: "Major_Defense_Flat",
-        	Attribute: CombatAttribute.Defense,
-        	ModifierType: AttributeModifierType.Flat,
-        	PrimaryStatsByLevel: null,
-        	SecondaryStatByRarityFrom: Create(50.0, 120.0, 200.0, 340.0, 460.0),
-        	SecondaryStatByRarityTo: Create(70.0, 140.0, 250.0, 400.0, 580.0),
-        	CalibrationStatsByLevel: null,
-        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
-    }
-
-    public static class Major_Defense_Perc
-    {
-        public static readonly UnitEquipmentAttributeDefinition Instance = new(
-        	Id: "Major_Defense_Perc",
-        	Attribute: CombatAttribute.Defense,
-        	ModifierType: AttributeModifierType.Percentage,
-        	PrimaryStatsByLevel: null,
-        	SecondaryStatByRarityFrom1: Create(.03, .05, .07, .1, .16),
-        	SecondaryStatByRarityTo: Create(.04, .06, .09, .15, .2),
-        	CalibrationStatsByLevel: null,
-        	UnitEquipmentSubType: UnitEquipmentSubType.Implant);
-    }
-}
\ No newline at end of file

From 39ba1bc3bb1f816eede68aea6b5640b85d890b41 Mon Sep 17 00:00:00 2001
From: Cyrus Najmabadi <cyrus.najmabadi@gmail.com>
Date: Fri, 30 May 2025 23:55:05 +0200
Subject: [PATCH 05/26] Update
 src/Compilers/CSharp/Test/Syntax/Parsing/RangeExpressionParsingTests.cs

---
 .../CSharp/Test/Syntax/Parsing/RangeExpressionParsingTests.cs   | 2 --
 1 file changed, 2 deletions(-)

diff --git a/src/Compilers/CSharp/Test/Syntax/Parsing/RangeExpressionParsingTests.cs b/src/Compilers/CSharp/Test/Syntax/Parsing/RangeExpressionParsingTests.cs
index 80a1153f48f42..3a3fc86d16063 100644
--- a/src/Compilers/CSharp/Test/Syntax/Parsing/RangeExpressionParsingTests.cs
+++ b/src/Compilers/CSharp/Test/Syntax/Parsing/RangeExpressionParsingTests.cs
@@ -2,8 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System.IO;
-using Roslyn.Test.Utilities;
 using Xunit;
 using Xunit.Abstractions;
 

From cab4c6b08fec91f6832cdbeea376d537ea1248ce Mon Sep 17 00:00:00 2001
From: Cyrus Najmabadi <cyrus.najmabadi@gmail.com>
Date: Fri, 30 May 2025 23:55:55 +0200
Subject: [PATCH 06/26] Update src/Compilers/CSharp/Test/Syntax/Resources.resx

---
 src/Compilers/CSharp/Test/Syntax/Resources.resx | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/Compilers/CSharp/Test/Syntax/Resources.resx b/src/Compilers/CSharp/Test/Syntax/Resources.resx
index 6cf8830fd0610..7306e0c5da8b4 100644
--- a/src/Compilers/CSharp/Test/Syntax/Resources.resx
+++ b/src/Compilers/CSharp/Test/Syntax/Resources.resx
@@ -1,4 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
+<!-- Licensed to the .NET Foundation under one or more agreements. The .NET Foundation licenses this file to you under the MIT license. See the LICENSE file in the project root for more information. -->
+
 <root>
   <!-- 
     Microsoft ResX Schema 

From 677dccce6e53b8ac1d9d96f30666dea1a5aceb9d Mon Sep 17 00:00:00 2001
From: Cyrus Najmabadi <cyrusn@microsoft.com>
Date: Mon, 2 Jun 2025 08:58:13 -0700
Subject: [PATCH 07/26] more explicit test

---
 .../Test/Syntax/LexicalAndXml/LexicalTests.cs | 56 +++++++++++++++++++
 1 file changed, 56 insertions(+)

diff --git a/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs b/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs
index c7b79fb5ca033..ead2ab6ffe18f 100644
--- a/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs
+++ b/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs
@@ -4581,6 +4581,62 @@ public void TestDotPrefixedNumberStartingAtStartOfSlidingTextWindow()
             // sliding text window, where the lexer tries to peek back one char to see if this
             // is actually `..0` (a range expr) or `.0` (a floating point number).
             CSharpSyntaxTree.ParseText(Resources.DotPrefixedNumberStartingAtStartOfSlidingTextWindow);
+
+            var lexer = new Lexer(
+                SourceText.From(Resources.DotPrefixedNumberStartingAtStartOfSlidingTextWindow),
+                CSharpParseOptions.Default);
+
+            // Now, replicate the same conditions that hte parser runs through by driving the a new lexer here
+            // directly.  That ensures that we are actually validating exactly the conditions that led to the bug
+            // (a dot token starting a number, right at the start of the character window).
+            var mode = LexerMode.Syntax;
+            for (var i = 0; i < 1327; i++)
+            {
+                if (i == 1326)
+                {
+                    // Ensure that the lexer's window is starting with the next FP number ("0.03") right at
+                    // the start of the window.
+                    Assert.True(lexer.TextWindow.CharacterWindow is ['.', '0', '3', ',', ..]);
+
+                    // Lexer will read from index 0 in the arrray.
+                    Assert.Equal(0, lexer.TextWindow.Offset);
+
+                    // We have 205 real chars in the window
+                    Assert.Equal(205, lexer.TextWindow.CharacterWindowCount);
+
+                    // The lexer is at position 10199 in the file.
+                    Assert.Equal(10199, lexer.TextWindow.Position);
+
+                    /// The 205 characters represent the final part of the doc
+                    Assert.Equal(lexer.TextWindow.Text.Length, lexer.TextWindow.Position + lexer.TextWindow.CharacterWindowCount);
+
+                    // We're at the start of a token.
+                    Assert.Equal(lexer.TextWindow.LexemeStartPosition, lexer.TextWindow.Position);
+
+                    var token = lexer.Lex(ref mode);
+                    Assert.Equal(SyntaxKind.NumericLiteralToken, token.Kind);
+                    Assert.Equal(3, token.FullWidth);
+                    Assert.Equal(".03", token.ToString());
+
+                    // Character window didn't changee.
+                    Assert.True(lexer.TextWindow.CharacterWindow is ['.', '0', '3', ',', ..]);
+
+                    // But we moved 3 characters forward.
+                    Assert.Equal(3, lexer.TextWindow.Offset);
+
+                    // We still have 205 real chars in the window
+                    Assert.Equal(205, lexer.TextWindow.CharacterWindowCount);
+
+                    // The lexer position has moved 3 characters forward as well.
+                    Assert.Equal(10202, lexer.TextWindow.Position);
+
+                    // We're at the start of a token.
+                    Assert.Equal(lexer.TextWindow.LexemeStartPosition, lexer.TextWindow.Position);
+                    break;
+                }
+
+                lexer.Lex(ref mode);
+            }
         }
     }
 }

From 0f251c4099e2641ba9e8b219fa4345ae9b8534e6 Mon Sep 17 00:00:00 2001
From: Cyrus Najmabadi <cyrusn@microsoft.com>
Date: Mon, 2 Jun 2025 09:04:58 -0700
Subject: [PATCH 08/26] poli

---
 src/Compilers/CSharp/Test/Syntax/Resources.resx | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/src/Compilers/CSharp/Test/Syntax/Resources.resx b/src/Compilers/CSharp/Test/Syntax/Resources.resx
index 7306e0c5da8b4..37ec16cc49bde 100644
--- a/src/Compilers/CSharp/Test/Syntax/Resources.resx
+++ b/src/Compilers/CSharp/Test/Syntax/Resources.resx
@@ -126,21 +126,21 @@
 // ------------------------------
 // Hash: D5-B1-B5-D5-B6-27-C1-44-E0-20-77-14-52-A7-7A-E3-26-1C-6C-74-82-E1-2D-00-C3-73-22-7D-F5-CF-1B-76-95-45-88-4A-9A-0D-E3-D1-8F-69-F3-C3-76-41-92-67-F1-9D-64-EF-86-77-39-48-8C-0E-20-44-51-CA-5D-65
 
-using Foobar.Combat;
-using Foobar.Commons.Rules;
-using Foobar.Localization;
-using Foobar.Shared.Entities.Units;
+using Goobar.Combat;
+using Goobar.Commons.Rules;
+using Goobar.Localization;
+using Goobar.Shared.Entities.Units;
 using static System.Collections.Immutable.ImmutableArray;
 using System;
 using System.Collections.Immutable;
-using Foobar.Shared.Utils;
+using Goobar.Shared.Utils;
 using System.Collections.Generic;
-using Foobar.GeneratedCode;
+using Goobar.GeneratedCode;
 
-namespace Foobar;
+namespace Goobar;
 
 
-[GenerateAllValues(typeof(Foobar.Commons.Rules.UnitEquipmentAttributeDefinition))]
+[GenerateAllValues(typeof(Goobar.Commons.Rules.UnitEquipmentAttributeDefinition))]
 public static partial class EquipmentAttributes
 {
 

From 719db9f6b624f101b1e956147ed481f76f738dba Mon Sep 17 00:00:00 2001
From: Cyrus Najmabadi <cyrusn@microsoft.com>
Date: Mon, 2 Jun 2025 09:06:26 -0700
Subject: [PATCH 09/26] test docs

---
 .../CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs   | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs b/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs
index ead2ab6ffe18f..ca0dd800ca05b 100644
--- a/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs
+++ b/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs
@@ -4576,19 +4576,21 @@ disabled text 2
         [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/78593")]
         public void TestDotPrefixedNumberStartingAtStartOfSlidingTextWindow()
         {
-            // This is the entire test.  We want to ensure this tree passes invariants.
             // It specifically validates what happens when we see `.0` at the start of the
             // sliding text window, where the lexer tries to peek back one char to see if this
             // is actually `..0` (a range expr) or `.0` (a floating point number).
+
+            // Do a full parse of the file that previous had broken parsing.  Running ParseText
+            // will ensure this tree passes invariants.  
             CSharpSyntaxTree.ParseText(Resources.DotPrefixedNumberStartingAtStartOfSlidingTextWindow);
 
+            // Now, replicate the same conditions that hte parser runs through by driving the a new lexer here
+            // directly.  That ensures that we are actually validating exactly the conditions that led to the bug
+            // (a dot token starting a number, right at the start of the character window).
             var lexer = new Lexer(
                 SourceText.From(Resources.DotPrefixedNumberStartingAtStartOfSlidingTextWindow),
                 CSharpParseOptions.Default);
 
-            // Now, replicate the same conditions that hte parser runs through by driving the a new lexer here
-            // directly.  That ensures that we are actually validating exactly the conditions that led to the bug
-            // (a dot token starting a number, right at the start of the character window).
             var mode = LexerMode.Syntax;
             for (var i = 0; i < 1327; i++)
             {

From 5fe9688d664c053db2cbbd37d296d9de6f0de74c Mon Sep 17 00:00:00 2001
From: Cyrus Najmabadi <cyrus.najmabadi@gmail.com>
Date: Mon, 2 Jun 2025 13:53:20 -0700
Subject: [PATCH 10/26] End of lines

---
 .../CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs        | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs b/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs
index ca0dd800ca05b..ad4485b265def 100644
--- a/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs
+++ b/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs
@@ -4576,6 +4576,12 @@ disabled text 2
         [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/78593")]
         public void TestDotPrefixedNumberStartingAtStartOfSlidingTextWindow()
         {
+            // This test depends on the line endings for the file being \r\n to ensure the right contents lines up at
+            // the right locations.
+            var code = Resources.DotPrefixedNumberStartingAtStartOfSlidingTextWindow;
+            if (!code.Contains("\r\n"))
+                code = code.Replace("\n", "\r\n");
+
             // It specifically validates what happens when we see `.0` at the start of the
             // sliding text window, where the lexer tries to peek back one char to see if this
             // is actually `..0` (a range expr) or `.0` (a floating point number).

From c16812e0fed5952f0dfb06f8248c93594e00ec7e Mon Sep 17 00:00:00 2001
From: Cyrus Najmabadi <cyrus.najmabadi@gmail.com>
Date: Mon, 2 Jun 2025 13:54:08 -0700
Subject: [PATCH 11/26] Fix comment

---
 src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs b/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs
index ad4485b265def..dca8bb9b499c7 100644
--- a/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs
+++ b/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs
@@ -4602,7 +4602,7 @@ public void TestDotPrefixedNumberStartingAtStartOfSlidingTextWindow()
             {
                 if (i == 1326)
                 {
-                    // Ensure that the lexer's window is starting with the next FP number ("0.03") right at
+                    // Ensure that the lexer's window is starting with the next FP number (".03") right at
                     // the start of the window.
                     Assert.True(lexer.TextWindow.CharacterWindow is ['.', '0', '3', ',', ..]);
 

From 810e9d446a4fb59ff8f13428cd3684eac99c4d0f Mon Sep 17 00:00:00 2001
From: Cyrus Najmabadi <cyrus.najmabadi@gmail.com>
Date: Mon, 2 Jun 2025 15:01:00 -0700
Subject: [PATCH 12/26] Update test

---
 .../CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs      | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs b/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs
index dca8bb9b499c7..f17e1343ac689 100644
--- a/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs
+++ b/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs
@@ -4582,20 +4582,20 @@ public void TestDotPrefixedNumberStartingAtStartOfSlidingTextWindow()
             if (!code.Contains("\r\n"))
                 code = code.Replace("\n", "\r\n");
 
+            var sourceText = SourceText.From(code);
+
             // It specifically validates what happens when we see `.0` at the start of the
             // sliding text window, where the lexer tries to peek back one char to see if this
             // is actually `..0` (a range expr) or `.0` (a floating point number).
 
             // Do a full parse of the file that previous had broken parsing.  Running ParseText
             // will ensure this tree passes invariants.  
-            CSharpSyntaxTree.ParseText(Resources.DotPrefixedNumberStartingAtStartOfSlidingTextWindow);
+            CSharpSyntaxTree.ParseText(sourceText);
 
             // Now, replicate the same conditions that hte parser runs through by driving the a new lexer here
             // directly.  That ensures that we are actually validating exactly the conditions that led to the bug
             // (a dot token starting a number, right at the start of the character window).
-            var lexer = new Lexer(
-                SourceText.From(Resources.DotPrefixedNumberStartingAtStartOfSlidingTextWindow),
-                CSharpParseOptions.Default);
+            var lexer = new Lexer(sourceText, CSharpParseOptions.Default);
 
             var mode = LexerMode.Syntax;
             for (var i = 0; i < 1327; i++)

From 919cc33c3fbcc5df39b43279da913abcff46937d Mon Sep 17 00:00:00 2001
From: Cyrus Najmabadi <cyrus.najmabadi@gmail.com>
Date: Mon, 2 Jun 2025 18:00:50 -0700
Subject: [PATCH 13/26] Update
 src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs

---
 src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs b/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs
index b50eff1e57941..10e171491452e 100644
--- a/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs
+++ b/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs
@@ -378,7 +378,7 @@ public char PreviousChar()
         {
             Debug.Assert(this.Position > 0);
             var desiredPosition = this.Position - 1;
-            if (desiredPosition >= _basis && _offset > 1)
+            if (desiredPosition >= _basis && _offset >= 1)
             {
                 // _basis describes where in the source text the current chunk of characters starts at.
                 // So if the desired position is ahead of that, then we can just read the value out of

From f22e03d2a97a65d719a1e5d0b286c802c0522ff2 Mon Sep 17 00:00:00 2001
From: Cyrus Najmabadi <cyrus.najmabadi@gmail.com>
Date: Tue, 3 Jun 2025 14:22:19 -0700
Subject: [PATCH 14/26] Apply suggestion from @CyrusNajmabadi

---
 src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs b/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs
index 10e171491452e..499a12c306ee6 100644
--- a/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs
+++ b/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs
@@ -378,7 +378,7 @@ public char PreviousChar()
         {
             Debug.Assert(this.Position > 0);
             var desiredPosition = this.Position - 1;
-            if (desiredPosition >= _basis && _offset >= 1)
+            if (desiredPosition >= _basis)
             {
                 // _basis describes where in the source text the current chunk of characters starts at.
                 // So if the desired position is ahead of that, then we can just read the value out of

From 6f57418909917fde5a94ff61924c3b8d5ee832f3 Mon Sep 17 00:00:00 2001
From: Cyrus Najmabadi <cyrus.najmabadi@gmail.com>
Date: Tue, 3 Jun 2025 16:53:54 -0700
Subject: [PATCH 15/26] Apply suggestion from @CyrusNajmabadi

---
 src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs b/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs
index 499a12c306ee6..de1a2663a1b07 100644
--- a/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs
+++ b/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs
@@ -378,7 +378,7 @@ public char PreviousChar()
         {
             Debug.Assert(this.Position > 0);
             var desiredPosition = this.Position - 1;
-            if (desiredPosition >= _basis)
+            if (desiredPosition > _basis)
             {
                 // _basis describes where in the source text the current chunk of characters starts at.
                 // So if the desired position is ahead of that, then we can just read the value out of

From b060dad00eb6a5f9d7f3bb42728350a28038d450 Mon Sep 17 00:00:00 2001
From: Cyrus Najmabadi <cyrus.najmabadi@gmail.com>
Date: Tue, 3 Jun 2025 16:54:20 -0700
Subject: [PATCH 16/26] Apply suggestion from @CyrusNajmabadi

---
 src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs b/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs
index de1a2663a1b07..499a12c306ee6 100644
--- a/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs
+++ b/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs
@@ -378,7 +378,7 @@ public char PreviousChar()
         {
             Debug.Assert(this.Position > 0);
             var desiredPosition = this.Position - 1;
-            if (desiredPosition > _basis)
+            if (desiredPosition >= _basis)
             {
                 // _basis describes where in the source text the current chunk of characters starts at.
                 // So if the desired position is ahead of that, then we can just read the value out of

From da18c86a35b59ad883d9cf14811e6e707ae0968a Mon Sep 17 00:00:00 2001
From: Cyrus Najmabadi <cyrus.najmabadi@gmail.com>
Date: Tue, 3 Jun 2025 17:07:42 -0700
Subject: [PATCH 17/26] Break out of loop

---
 .../Test/Syntax/LexicalAndXml/LexicalTests.cs | 64 +++++++++----------
 1 file changed, 29 insertions(+), 35 deletions(-)

diff --git a/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs b/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs
index f17e1343ac689..8848518ee89fb 100644
--- a/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs
+++ b/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs
@@ -4598,53 +4598,47 @@ public void TestDotPrefixedNumberStartingAtStartOfSlidingTextWindow()
             var lexer = new Lexer(sourceText, CSharpParseOptions.Default);
 
             var mode = LexerMode.Syntax;
-            for (var i = 0; i < 1327; i++)
-            {
-                if (i == 1326)
-                {
-                    // Ensure that the lexer's window is starting with the next FP number (".03") right at
-                    // the start of the window.
-                    Assert.True(lexer.TextWindow.CharacterWindow is ['.', '0', '3', ',', ..]);
+            for (var i = 0; i < 1326; i++)
+                lexer.Lex(ref mode);
 
-                    // Lexer will read from index 0 in the arrray.
-                    Assert.Equal(0, lexer.TextWindow.Offset);
+            // Ensure that the lexer's window is starting with the next FP number (".03") right at
+            // the start of the window.
+            Assert.True(lexer.TextWindow.CharacterWindow is ['.', '0', '3', ',', ..]);
 
-                    // We have 205 real chars in the window
-                    Assert.Equal(205, lexer.TextWindow.CharacterWindowCount);
+            // Lexer will read from index 0 in the arrray.
+            Assert.Equal(0, lexer.TextWindow.Offset);
 
-                    // The lexer is at position 10199 in the file.
-                    Assert.Equal(10199, lexer.TextWindow.Position);
+            // We have 205 real chars in the window
+            Assert.Equal(205, lexer.TextWindow.CharacterWindowCount);
 
-                    /// The 205 characters represent the final part of the doc
-                    Assert.Equal(lexer.TextWindow.Text.Length, lexer.TextWindow.Position + lexer.TextWindow.CharacterWindowCount);
+            // The lexer is at position 10199 in the file.
+            Assert.Equal(10199, lexer.TextWindow.Position);
 
-                    // We're at the start of a token.
-                    Assert.Equal(lexer.TextWindow.LexemeStartPosition, lexer.TextWindow.Position);
+            /// The 205 characters represent the final part of the doc
+            Assert.Equal(lexer.TextWindow.Text.Length, lexer.TextWindow.Position + lexer.TextWindow.CharacterWindowCount);
 
-                    var token = lexer.Lex(ref mode);
-                    Assert.Equal(SyntaxKind.NumericLiteralToken, token.Kind);
-                    Assert.Equal(3, token.FullWidth);
-                    Assert.Equal(".03", token.ToString());
+            // We're at the start of a token.
+            Assert.Equal(lexer.TextWindow.LexemeStartPosition, lexer.TextWindow.Position);
 
-                    // Character window didn't changee.
-                    Assert.True(lexer.TextWindow.CharacterWindow is ['.', '0', '3', ',', ..]);
+            var token = lexer.Lex(ref mode);
+            Assert.Equal(SyntaxKind.NumericLiteralToken, token.Kind);
+            Assert.Equal(3, token.FullWidth);
+            Assert.Equal(".03", token.ToString());
 
-                    // But we moved 3 characters forward.
-                    Assert.Equal(3, lexer.TextWindow.Offset);
+            // Character window didn't changee.
+            Assert.True(lexer.TextWindow.CharacterWindow is ['.', '0', '3', ',', ..]);
 
-                    // We still have 205 real chars in the window
-                    Assert.Equal(205, lexer.TextWindow.CharacterWindowCount);
+            // But we moved 3 characters forward.
+            Assert.Equal(3, lexer.TextWindow.Offset);
 
-                    // The lexer position has moved 3 characters forward as well.
-                    Assert.Equal(10202, lexer.TextWindow.Position);
+            // We still have 205 real chars in the window
+            Assert.Equal(205, lexer.TextWindow.CharacterWindowCount);
 
-                    // We're at the start of a token.
-                    Assert.Equal(lexer.TextWindow.LexemeStartPosition, lexer.TextWindow.Position);
-                    break;
-                }
+            // The lexer position has moved 3 characters forward as well.
+            Assert.Equal(10202, lexer.TextWindow.Position);
 
-                lexer.Lex(ref mode);
-            }
+            // We're at the start of a token.
+            Assert.Equal(lexer.TextWindow.LexemeStartPosition, lexer.TextWindow.Position);
         }
     }
 }

From c9c507a70c045a7e18f3c01a586301ae505d108b Mon Sep 17 00:00:00 2001
From: Cyrus Najmabadi <cyrusn@microsoft.com>
Date: Tue, 3 Jun 2025 19:28:15 -0700
Subject: [PATCH 18/26] Restore

---
 src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs b/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs
index 499a12c306ee6..10e171491452e 100644
--- a/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs
+++ b/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs
@@ -378,7 +378,7 @@ public char PreviousChar()
         {
             Debug.Assert(this.Position > 0);
             var desiredPosition = this.Position - 1;
-            if (desiredPosition >= _basis)
+            if (desiredPosition >= _basis && _offset >= 1)
             {
                 // _basis describes where in the source text the current chunk of characters starts at.
                 // So if the desired position is ahead of that, then we can just read the value out of

From 12caf417ed394bdcf5dadd123786d662945e3a0a Mon Sep 17 00:00:00 2001
From: Cyrus Najmabadi <cyrusn@microsoft.com>
Date: Tue, 3 Jun 2025 20:46:04 -0700
Subject: [PATCH 19/26] Reorder

---
 .../Test/Syntax/LexicalAndXml/LexicalTests.cs      | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs b/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs
index 8848518ee89fb..fbf0680fe7567 100644
--- a/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs
+++ b/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs
@@ -4601,10 +4601,6 @@ public void TestDotPrefixedNumberStartingAtStartOfSlidingTextWindow()
             for (var i = 0; i < 1326; i++)
                 lexer.Lex(ref mode);
 
-            // Ensure that the lexer's window is starting with the next FP number (".03") right at
-            // the start of the window.
-            Assert.True(lexer.TextWindow.CharacterWindow is ['.', '0', '3', ',', ..]);
-
             // Lexer will read from index 0 in the arrray.
             Assert.Equal(0, lexer.TextWindow.Offset);
 
@@ -4620,14 +4616,15 @@ public void TestDotPrefixedNumberStartingAtStartOfSlidingTextWindow()
             // We're at the start of a token.
             Assert.Equal(lexer.TextWindow.LexemeStartPosition, lexer.TextWindow.Position);
 
+            // Ensure that the lexer's window is starting with the next FP number (".03") right at
+            // the start of the window.
+            Assert.True(lexer.TextWindow.CharacterWindow is ['.', '0', '3', ',', ..]);
+
             var token = lexer.Lex(ref mode);
             Assert.Equal(SyntaxKind.NumericLiteralToken, token.Kind);
             Assert.Equal(3, token.FullWidth);
             Assert.Equal(".03", token.ToString());
 
-            // Character window didn't changee.
-            Assert.True(lexer.TextWindow.CharacterWindow is ['.', '0', '3', ',', ..]);
-
             // But we moved 3 characters forward.
             Assert.Equal(3, lexer.TextWindow.Offset);
 
@@ -4639,6 +4636,9 @@ public void TestDotPrefixedNumberStartingAtStartOfSlidingTextWindow()
 
             // We're at the start of a token.
             Assert.Equal(lexer.TextWindow.LexemeStartPosition, lexer.TextWindow.Position);
+
+            // Character window didn't changee.
+            Assert.True(lexer.TextWindow.CharacterWindow is ['.', '0', '3', ',', ..]);
         }
     }
 }

From 95287c486ded733d5f811e93bd94bc5c5a340ab6 Mon Sep 17 00:00:00 2001
From: Cyrus Najmabadi <cyrusn@microsoft.com>
Date: Tue, 3 Jun 2025 20:48:10 -0700
Subject: [PATCH 20/26] More assert info

---
 src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs     | 2 +-
 .../CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs          | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs b/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs
index 10e171491452e..c41cb895a70d4 100644
--- a/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs
+++ b/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs
@@ -378,7 +378,7 @@ public char PreviousChar()
         {
             Debug.Assert(this.Position > 0);
             var desiredPosition = this.Position - 1;
-            if (desiredPosition >= _basis && _offset >= 1)
+            if (desiredPosition >= _basis/* && _offset >= 1*/)
             {
                 // _basis describes where in the source text the current chunk of characters starts at.
                 // So if the desired position is ahead of that, then we can just read the value out of
diff --git a/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs b/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs
index fbf0680fe7567..315b590f4f6d5 100644
--- a/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs
+++ b/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs
@@ -4618,7 +4618,7 @@ public void TestDotPrefixedNumberStartingAtStartOfSlidingTextWindow()
 
             // Ensure that the lexer's window is starting with the next FP number (".03") right at
             // the start of the window.
-            Assert.True(lexer.TextWindow.CharacterWindow is ['.', '0', '3', ',', ..]);
+            Assert.True(lexer.TextWindow.CharacterWindow is ['.', '0', '3', ',', ..], $"Start of window was '{new string(lexer.TextWindow.CharacterWindow, 0, 4)}'");
 
             var token = lexer.Lex(ref mode);
             Assert.Equal(SyntaxKind.NumericLiteralToken, token.Kind);
@@ -4638,7 +4638,7 @@ public void TestDotPrefixedNumberStartingAtStartOfSlidingTextWindow()
             Assert.Equal(lexer.TextWindow.LexemeStartPosition, lexer.TextWindow.Position);
 
             // Character window didn't changee.
-            Assert.True(lexer.TextWindow.CharacterWindow is ['.', '0', '3', ',', ..]);
+            Assert.True(lexer.TextWindow.CharacterWindow is ['.', '0', '3', ',', ..], $"Start of window was '{new string(lexer.TextWindow.CharacterWindow, 0, 4)}'");
         }
     }
 }

From 1babb66f112ecb21288bf33e67f756089706dbe5 Mon Sep 17 00:00:00 2001
From: Cyrus Najmabadi <cyrusn@microsoft.com>
Date: Tue, 3 Jun 2025 22:00:53 -0700
Subject: [PATCH 21/26] restore

---
 src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs b/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs
index c41cb895a70d4..10e171491452e 100644
--- a/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs
+++ b/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs
@@ -378,7 +378,7 @@ public char PreviousChar()
         {
             Debug.Assert(this.Position > 0);
             var desiredPosition = this.Position - 1;
-            if (desiredPosition >= _basis/* && _offset >= 1*/)
+            if (desiredPosition >= _basis && _offset >= 1)
             {
                 // _basis describes where in the source text the current chunk of characters starts at.
                 // So if the desired position is ahead of that, then we can just read the value out of

From 241b28b00925c196d340ad34b8a510c3cb043a66 Mon Sep 17 00:00:00 2001
From: Cyrus Najmabadi <cyrus.najmabadi@gmail.com>
Date: Wed, 4 Jun 2025 07:56:35 -0700
Subject: [PATCH 22/26] Change logic and tweak test

---
 .../Portable/Parser/SlidingTextWindow.cs      | 26 +++--
 .../Test/Syntax/LexicalAndXml/LexicalTests.cs | 98 +++++++++++--------
 .../Portable/Syntax/SyntaxTreeExtensions.cs   |  9 +-
 3 files changed, 81 insertions(+), 52 deletions(-)

diff --git a/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs b/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs
index 10e171491452e..7ce4ce8af1d76 100644
--- a/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs
+++ b/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs
@@ -3,12 +3,8 @@
 // See the LICENSE file in the project root for more information.
 
 using System;
-using System.Collections.Concurrent;
 using System.Diagnostics;
 using System.Text;
-using Microsoft.CodeAnalysis.Collections;
-using Microsoft.CodeAnalysis.CSharp.Symbols;
-using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.PooledObjects;
 using Microsoft.CodeAnalysis.Text;
 using Roslyn.Utilities;
@@ -377,12 +373,11 @@ public char PeekChar(int delta)
         public char PreviousChar()
         {
             Debug.Assert(this.Position > 0);
-            var desiredPosition = this.Position - 1;
-            if (desiredPosition >= _basis && _offset >= 1)
+            if (_offset > 0)
             {
-                // _basis describes where in the source text the current chunk of characters starts at.
-                // So if the desired position is ahead of that, then we can just read the value out of
-                // the character window directly.
+                // The allowed region of the window that can be read is from 0 to _characterWindowCount (which _offset)
+                // is in between.  So as long as _offset is greater than 0, we can read the previous character directly
+                // from the current chunk of characters in the window.
                 return this.CharacterWindow[_offset - 1];
             }
 
@@ -391,7 +386,7 @@ public char PreviousChar()
             // Just go back to the source text to find this character.  While more expensive, this should
             // be rare given that most of the time we won't be calling this right after loading a new text
             // chunk.
-            return this.Text[desiredPosition];
+            return this.Text[this.Position - 1];
         }
 
         /// <summary>
@@ -500,5 +495,16 @@ internal static char GetCharsFromUtf32(uint codepoint, out char lowSurrogate)
                 return (char)((codepoint - 0x00010000) / 0x0400 + 0xD800);
             }
         }
+
+        public TestAccessor GetTestAccessor()
+            => new(this);
+
+        public readonly struct TestAccessor(SlidingTextWindow window)
+        {
+            private readonly SlidingTextWindow _window = window;
+
+            public void SetDefaultCharacterWindow()
+                => _window._characterWindow = new char[DefaultWindowLength];
+        }
     }
 }
diff --git a/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs b/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs
index 315b590f4f6d5..a2360d1bf4c0d 100644
--- a/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs
+++ b/src/Compilers/CSharp/Test/Syntax/LexicalAndXml/LexicalTests.cs
@@ -8,6 +8,7 @@
 using System.Collections.Generic;
 using System.Globalization;
 using System.Linq;
+using System.Threading;
 using Microsoft.CodeAnalysis.CSharp.Syntax.InternalSyntax;
 using Microsoft.CodeAnalysis.CSharp.Test.Utilities;
 using Microsoft.CodeAnalysis.Text;
@@ -4578,67 +4579,84 @@ public void TestDotPrefixedNumberStartingAtStartOfSlidingTextWindow()
         {
             // This test depends on the line endings for the file being \r\n to ensure the right contents lines up at
             // the right locations.
+            //
+            // It specifically validates what happens when we see `.0` at the start of the
+            // sliding text window, where the lexer tries to peek back one char to see if this
+            // is actually `..0` (a range expr) or `.0` (a floating point number).
             var code = Resources.DotPrefixedNumberStartingAtStartOfSlidingTextWindow;
             if (!code.Contains("\r\n"))
                 code = code.Replace("\n", "\r\n");
 
             var sourceText = SourceText.From(code);
 
-            // It specifically validates what happens when we see `.0` at the start of the
-            // sliding text window, where the lexer tries to peek back one char to see if this
-            // is actually `..0` (a range expr) or `.0` (a floating point number).
+            {
+                // Run a full parse, and validate the tree returned).
 
-            // Do a full parse of the file that previous had broken parsing.  Running ParseText
-            // will ensure this tree passes invariants.  
-            CSharpSyntaxTree.ParseText(sourceText);
+                using var lexer = new Lexer(sourceText, CSharpParseOptions.Default);
 
-            // Now, replicate the same conditions that hte parser runs through by driving the a new lexer here
-            // directly.  That ensures that we are actually validating exactly the conditions that led to the bug
-            // (a dot token starting a number, right at the start of the character window).
-            var lexer = new Lexer(sourceText, CSharpParseOptions.Default);
+                // Ensure we have a normal window size, not some larger array that another test created and cached in
+                // the window pool
+                lexer.TextWindow.GetTestAccessor().SetDefaultCharacterWindow();
 
-            var mode = LexerMode.Syntax;
-            for (var i = 0; i < 1326; i++)
-                lexer.Lex(ref mode);
+                using var parser = new LanguageParser(lexer, oldTree: null, changes: null);
 
-            // Lexer will read from index 0 in the arrray.
-            Assert.Equal(0, lexer.TextWindow.Offset);
+                Microsoft.CodeAnalysis.SyntaxTreeExtensions.VerifySource(
+                    sourceText, parser.ParseCompilationUnit().CreateRed());
+            }
+
+            {
+                // Now, replicate the same conditions that hte parser runs through by driving the a new lexer here
+                // directly.  That ensures that we are actually validating exactly the conditions that led to the bug
+                // (a dot token starting a number, right at the start of the character window).
+                var lexer = new Lexer(sourceText, CSharpParseOptions.Default);
+
+                // Ensure we have a normal window size, not some larger array that another test created and cached in
+                // the window pool
+                lexer.TextWindow.GetTestAccessor().SetDefaultCharacterWindow();
 
-            // We have 205 real chars in the window
-            Assert.Equal(205, lexer.TextWindow.CharacterWindowCount);
+                var mode = LexerMode.Syntax;
+                for (var i = 0; i < 1326; i++)
+                    lexer.Lex(ref mode);
 
-            // The lexer is at position 10199 in the file.
-            Assert.Equal(10199, lexer.TextWindow.Position);
+                // Lexer will read from index 0 in the arrray.
+                Assert.Equal(0, lexer.TextWindow.Offset);
 
-            /// The 205 characters represent the final part of the doc
-            Assert.Equal(lexer.TextWindow.Text.Length, lexer.TextWindow.Position + lexer.TextWindow.CharacterWindowCount);
+                // We have 205 real chars in the window
+                Assert.Equal(205, lexer.TextWindow.CharacterWindowCount);
 
-            // We're at the start of a token.
-            Assert.Equal(lexer.TextWindow.LexemeStartPosition, lexer.TextWindow.Position);
+                // The lexer is at position 10199 in the file.
+                Assert.Equal(10199, lexer.TextWindow.Position);
 
-            // Ensure that the lexer's window is starting with the next FP number (".03") right at
-            // the start of the window.
-            Assert.True(lexer.TextWindow.CharacterWindow is ['.', '0', '3', ',', ..], $"Start of window was '{new string(lexer.TextWindow.CharacterWindow, 0, 4)}'");
+                /// The 205 characters represent the final part of the doc
+                Assert.Equal(lexer.TextWindow.Text.Length, lexer.TextWindow.Position + lexer.TextWindow.CharacterWindowCount);
 
-            var token = lexer.Lex(ref mode);
-            Assert.Equal(SyntaxKind.NumericLiteralToken, token.Kind);
-            Assert.Equal(3, token.FullWidth);
-            Assert.Equal(".03", token.ToString());
+                // We're at the start of a token.
+                Assert.Equal(lexer.TextWindow.LexemeStartPosition, lexer.TextWindow.Position);
 
-            // But we moved 3 characters forward.
-            Assert.Equal(3, lexer.TextWindow.Offset);
+                // Ensure that the lexer's window is starting with the next FP number (".03") right at
+                // the start of the window.
+                Assert.True(lexer.TextWindow.CharacterWindow is ['.', '0', '3', ',', ..], $"Start of window was '{new string(lexer.TextWindow.CharacterWindow, 0, 4)}'");
 
-            // We still have 205 real chars in the window
-            Assert.Equal(205, lexer.TextWindow.CharacterWindowCount);
+                var token = lexer.Lex(ref mode);
+                Assert.Equal(SyntaxKind.NumericLiteralToken, token.Kind);
+                Assert.Equal(3, token.FullWidth);
+                Assert.Equal(".03", token.ToString());
 
-            // The lexer position has moved 3 characters forward as well.
-            Assert.Equal(10202, lexer.TextWindow.Position);
+                // But we moved 3 characters forward.
+                Assert.Equal(3, lexer.TextWindow.Offset);
 
-            // We're at the start of a token.
-            Assert.Equal(lexer.TextWindow.LexemeStartPosition, lexer.TextWindow.Position);
+                // We still have 205 real chars in the window
+                Assert.Equal(205, lexer.TextWindow.CharacterWindowCount);
 
-            // Character window didn't changee.
-            Assert.True(lexer.TextWindow.CharacterWindow is ['.', '0', '3', ',', ..], $"Start of window was '{new string(lexer.TextWindow.CharacterWindow, 0, 4)}'");
+                // The lexer position has moved 3 characters forward as well.
+                Assert.Equal(10202, lexer.TextWindow.Position);
+
+                // We're at the start of a token.
+                Assert.Equal(lexer.TextWindow.LexemeStartPosition, lexer.TextWindow.Position);
+
+                // Character window didn't changee.
+                Assert.True(lexer.TextWindow.CharacterWindow is ['.', '0', '3', ',', ..], $"Start of window was '{new string(lexer.TextWindow.CharacterWindow, 0, 4)}'");
+            }
         }
     }
 }
diff --git a/src/Compilers/Core/Portable/Syntax/SyntaxTreeExtensions.cs b/src/Compilers/Core/Portable/Syntax/SyntaxTreeExtensions.cs
index 39dc59103b1ab..7422b9c1882ca 100644
--- a/src/Compilers/Core/Portable/Syntax/SyntaxTreeExtensions.cs
+++ b/src/Compilers/Core/Portable/Syntax/SyntaxTreeExtensions.cs
@@ -19,8 +19,13 @@ internal static class SyntaxTreeExtensions
         [Conditional("DEBUG")]
         internal static void VerifySource(this SyntaxTree tree, IEnumerable<TextChangeRange>? changes = null)
         {
-            var root = tree.GetRoot();
-            var text = tree.GetText();
+            VerifySource(tree.GetText(), tree.GetRoot(), changes);
+        }
+
+        /// <inheritdoc cref="VerifySource(SyntaxTree, IEnumerable{TextChangeRange}?)"/>
+        [Conditional("DEBUG")]
+        internal static void VerifySource(SourceText text, SyntaxNode root, IEnumerable<TextChangeRange>? changes = null)
+        {
             var fullSpan = new TextSpan(0, text.Length);
             SyntaxNode? node = null;
 

From bec86130ce5ed5093b35d4e74f593a2ac3895d25 Mon Sep 17 00:00:00 2001
From: Cyrus Najmabadi <cyrus.najmabadi@gmail.com>
Date: Thu, 5 Jun 2025 06:39:01 -0700
Subject: [PATCH 23/26] Update
 src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs

Co-authored-by: Fred Silberberg <fred@silberberg.xyz>
---
 src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs b/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs
index 7ce4ce8af1d76..8cecb41c718f0 100644
--- a/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs
+++ b/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs
@@ -375,8 +375,8 @@ public char PreviousChar()
             Debug.Assert(this.Position > 0);
             if (_offset > 0)
             {
-                // The allowed region of the window that can be read is from 0 to _characterWindowCount (which _offset)
-                // is in between.  So as long as _offset is greater than 0, we can read the previous character directly
+                // The allowed region of the window that can be read is from 0 to _characterWindowCount (which _offset
+                // is in between).  So as long as _offset is greater than 0, we can read the previous character directly
                 // from the current chunk of characters in the window.
                 return this.CharacterWindow[_offset - 1];
             }

From 065f3b29c3f0ceafbeed946ef7913c310676dfce Mon Sep 17 00:00:00 2001
From: Cyrus Najmabadi <cyrusn@microsoft.com>
Date: Thu, 5 Jun 2025 06:41:07 -0700
Subject: [PATCH 24/26] Remove target typed new

---
 src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs b/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs
index 8cecb41c718f0..b784d70b9ab21 100644
--- a/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs
+++ b/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs
@@ -497,7 +497,7 @@ internal static char GetCharsFromUtf32(uint codepoint, out char lowSurrogate)
         }
 
         public TestAccessor GetTestAccessor()
-            => new(this);
+            => new TestAccessor(this);
 
         public readonly struct TestAccessor(SlidingTextWindow window)
         {

From 04c5811dcf0808f4585fe322b96ff1893b849dca Mon Sep 17 00:00:00 2001
From: Cyrus Najmabadi <cyrusn@microsoft.com>
Date: Thu, 5 Jun 2025 06:41:45 -0700
Subject: [PATCH 25/26] Switch to internal

---
 src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs b/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs
index b784d70b9ab21..6e39642976469 100644
--- a/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs
+++ b/src/Compilers/CSharp/Portable/Parser/SlidingTextWindow.cs
@@ -496,14 +496,14 @@ internal static char GetCharsFromUtf32(uint codepoint, out char lowSurrogate)
             }
         }
 
-        public TestAccessor GetTestAccessor()
+        internal TestAccessor GetTestAccessor()
             => new TestAccessor(this);
 
-        public readonly struct TestAccessor(SlidingTextWindow window)
+        internal readonly struct TestAccessor(SlidingTextWindow window)
         {
             private readonly SlidingTextWindow _window = window;
 
-            public void SetDefaultCharacterWindow()
+            internal void SetDefaultCharacterWindow()
                 => _window._characterWindow = new char[DefaultWindowLength];
         }
     }

From b9097ed9780ad33e80afc69eabc183a578bde792 Mon Sep 17 00:00:00 2001
From: Cyrus Najmabadi <cyrusn@microsoft.com>
Date: Thu, 5 Jun 2025 06:52:25 -0700
Subject: [PATCH 26/26] Inline

---
 src/Compilers/CSharp/Portable/Parser/Lexer.cs | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/src/Compilers/CSharp/Portable/Parser/Lexer.cs b/src/Compilers/CSharp/Portable/Parser/Lexer.cs
index 68132539cac0f..df472c8733279 100644
--- a/src/Compilers/CSharp/Portable/Parser/Lexer.cs
+++ b/src/Compilers/CSharp/Portable/Parser/Lexer.cs
@@ -475,9 +475,7 @@ private void ScanSyntaxToken(ref TokenInfo info)
                             // dots followed by an integer (which will be treated as a range expression).
                             //
                             // Move back one space to see what's before this dot and adjust accordingly.
-
-                            var priorCharacterIsDot = this.TextWindow.PreviousChar() is '.';
-                            if (priorCharacterIsDot)
+                            if (this.TextWindow.PreviousChar() is '.')
                             {
                                 // We have two dots in a row.  Treat the second dot as a dot, not the start of a number literal.
                                 TextWindow.AdvanceChar();