Require spaces within line span directives and relax LangVer check

docs/compilers/CSharp/Compiler Breaking Changes - DotNet 7.md

@@ -1,5 +1,16 @@
 # This document lists known breaking changes in Roslyn after .NET 6 all the way to .NET 7.
 
+## Required spaces in #line span directives
+
+***Introduced in .NET SDK 6.0.400, Visual Studio 2022 version 17.3.***
+
+When the `#line` span directive was introduced in C# 10, it required no particular spacing.  
+For example, this would be valid: `#line(1,2)-(3,4)5"file.cs"`.
+
+In Visual Studio 17.3, the compiler requires spaces before the first parenthesis, the character
+offset, and the file name.  
+So the above example fails to parse unless spaces are added: `#line (1,2)-(3,4) 5 "file.cs"`.
+
 ## Checked operators on System.IntPtr and System.UIntPtr
 
 ***Introduced in .NET SDK 7.0.100, Visual Studio 2022 version 17.3.***

src/Compilers/CSharp/Portable/CSharpResources.resx

@@ -6670,9 +6670,6 @@ To remove the warning, you can use /reference instead (set the Embed Interop Typ
   <data name="IDS_FeatureInferredDelegateType" xml:space="preserve">
     <value>inferred delegate type</value>
   </data>
-  <data name="IDS_FeatureLineSpanDirective" xml:space="preserve">
-    <value>line span directive</value>
-  </data>
   <data name="IDS_FeatureAutoDefaultStructs" xml:space="preserve">
     <value>auto default struct fields</value>
   </data>
@@ -6682,6 +6679,9 @@ To remove the warning, you can use /reference instead (set the Embed Interop Typ
   <data name="ERR_LineSpanDirectiveEndLessThanStart" xml:space="preserve">
     <value>The #line directive end position must be greater than or equal to the start position</value>
   </data>
+  <data name="ERR_LineSpanDirectiveRequiresSpace" xml:space="preserve">
+    <value>The #line span directive requires space before the first parenthesis, before the character offset, and before the file name</value>
+  </data>
   <data name="WRN_DoNotCompareFunctionPointers" xml:space="preserve">
     <value>Comparison of function pointers might yield an unexpected result, since pointers to the same function may be distinct.</value>
   </data>

src/Compilers/CSharp/Portable/Errors/ErrorCode.cs

@@ -2071,6 +2071,7 @@ internal enum ErrorCode
 
         ERR_CannotBeConvertedToUTF8 = 9026,
         ERR_MisplacedUnchecked = 9027,
+        ERR_LineSpanDirectiveRequiresSpace = 9028,
 
         ERR_RequiredNameDisallowed = 9029,
         ERR_OverrideMustHaveRequired = 9030,

src/Compilers/CSharp/Portable/Errors/MessageID.cs

@@ -230,7 +230,7 @@ internal enum MessageID
         IDS_FeatureLambdaReturnType = MessageBase + 12804,
         IDS_AsyncMethodBuilderOverride = MessageBase + 12805,
         IDS_FeatureImplicitImplementationOfNonPublicMembers = MessageBase + 12806,
-        IDS_FeatureLineSpanDirective = MessageBase + 12807,
+        // IDS_FeatureLineSpanDirective = MessageBase + 12807, // feature no longer gated on LangVer
         IDS_FeatureImprovedInterpolatedStrings = MessageBase + 12808,
         IDS_FeatureFileScopedNamespace = MessageBase + 12809,
         IDS_FeatureParameterlessStructConstructors = MessageBase + 12810,
@@ -396,7 +396,6 @@ internal static LanguageVersion RequiredVersion(this MessageID feature)
                 case MessageID.IDS_AsyncMethodBuilderOverride: // semantic check
                 case MessageID.IDS_FeatureConstantInterpolatedStrings: // semantic check
                 case MessageID.IDS_FeatureImplicitImplementationOfNonPublicMembers: // semantic check
-                case MessageID.IDS_FeatureLineSpanDirective:
                 case MessageID.IDS_FeatureFileScopedNamespace: // syntax check
                 case MessageID.IDS_FeatureParameterlessStructConstructors: // semantic check
                 case MessageID.IDS_FeatureStructFieldInitializers: // semantic check

src/Compilers/CSharp/Portable/Parser/DirectiveParser.cs

@@ -406,13 +406,12 @@ private LineSpanDirectiveTriviaSyntax ParseLineSpanDirective(SyntaxToken hash, S
         {
             Debug.Assert(CurrentToken.Kind == SyntaxKind.OpenParenToken);
 
-            if (isActive)
-            {
-                lineKeyword = CheckFeatureAvailability(lineKeyword, MessageID.IDS_FeatureLineSpanDirective);
-            }
-
             bool reportError = isActive;
             var start = ParseLineDirectivePosition(ref reportError, out int startLine, out int startCharacter);
+            if (noTriviaBetween(lineKeyword, start.GetFirstToken()))
+            {
+                start = this.AddError(start, ErrorCode.ERR_LineSpanDirectiveRequiresSpace);
+            }
 
             var minus = EatToken(SyntaxKind.MinusToken, reportError: reportError);
             if (minus.IsMissing) reportError = false;
@@ -428,11 +427,28 @@ private LineSpanDirectiveTriviaSyntax ParseLineSpanDirective(SyntaxToken hash, S
                 ParseLineDirectiveNumericLiteral(ref reportError, minValue: 1, maxValue: MaxCharacterValue, out _) :
                 null;
 
+            if (noTriviaBetween(end.GetLastToken(), characterOffset))
+            {
+                characterOffset = this.AddError(characterOffset, ErrorCode.ERR_LineSpanDirectiveRequiresSpace);
+            }
+
             var file = EatToken(SyntaxKind.StringLiteralToken, ErrorCode.ERR_MissingPPFile, reportError: reportError);
             if (file.IsMissing) reportError = false;
 
+            if (noTriviaBetween(characterOffset ?? end.GetLastToken(), file))
+            {
+                file = this.AddError(file, ErrorCode.ERR_LineSpanDirectiveRequiresSpace);
+            }
+
             var endOfDirective = this.ParseEndOfDirective(ignoreErrors: !reportError);
             return SyntaxFactory.LineSpanDirectiveTrivia(hash, lineKeyword, start, minus, end, characterOffset, file, endOfDirective, isActive);
+
+            static bool noTriviaBetween(SyntaxToken token1, SyntaxToken token2)
+            {
+                return token1 is { IsMissing: false }
+                    && token2 is { IsMissing: false }
+                    && LanguageParser.NoTriviaBetween(token1, token2);
+            }
         }
 
         private LineDirectivePositionSyntax ParseLineDirectivePosition(ref bool reportError, out int line, out int character)

src/Compilers/CSharp/Portable/Parser/LanguageParser.cs

@@ -4596,7 +4596,7 @@ private void ParseParameterNullCheck(
                 GetExpectedTokenError(kind, t1.Kind));
         }
 
-        private static bool NoTriviaBetween(SyntaxToken token1, SyntaxToken token2)
+        internal static bool NoTriviaBetween(SyntaxToken token1, SyntaxToken token2)
             => token1.GetTrailingTriviaWidth() == 0 && token2.GetLeadingTriviaWidth() == 0;
 
 #nullable disable