Use struct tuple instead of reference tuple for pair ordering (#18513)

Author: brianrourkeboll

src/Compiler/Optimize/InnerLambdasToTopLevelFuncs.fs

@@ -330,8 +330,8 @@ type ReqdItem =
 
 let reqdItemOrder =
     let rep = function
-      | ReqdSubEnv v -> true, v
-      | ReqdVal    v -> false, v
+      | ReqdSubEnv v -> struct (true, v)
+      | ReqdVal    v -> struct (false, v)
 
     Order.orderOn rep (Pair.order (Bool.order, valOrder))
 

src/Compiler/Utilities/lib.fs

@@ -59,12 +59,11 @@ module Int64 =
 
 module Pair =
     let order (compare1: IComparer<'T1>, compare2: IComparer<'T2>) =
-        { new IComparer<'T1 * 'T2> with
+        { new IComparer<struct ('T1 * 'T2)> with
              member _.Compare((a1, a2), (aa1, aa2)) =
                   let res1 = compare1.Compare (a1, aa1)
                   if res1 <> 0 then res1 else compare2.Compare (a2, aa2) }
 
-
 type NameSet =  Zset<string>
 
 module NameSet =

src/Compiler/Utilities/lib.fsi

@@ -52,7 +52,7 @@ module Int64 =
     val order: IComparer<int64>
 
 module Pair =
-    val order: compare1: IComparer<'T1> * compare2: IComparer<'T2> -> IComparer<'T1 * 'T2>
+    val order: compare1: IComparer<'T1> * compare2: IComparer<'T2> -> IComparer<struct ('T1 * 'T2)>
 
 type NameSet = Zset<string>
 

src/Compiler/Utilities/range.fs

@@ -449,7 +449,7 @@ module Range =
 
     let posOrder =
         let pairOrder = Pair.order (Int32.order, Int32.order)
-        let lineAndColumn = fun (p: pos) -> p.Line, p.Column
+        let lineAndColumn = fun (p: pos) -> struct (p.Line, p.Column)
 
         { new IComparer<pos> with
             member _.Compare(x, xx) =
@@ -458,7 +458,7 @@ module Range =
 
     let rangeOrder =
         let tripleOrder = Pair.order (String.order, Pair.order (posOrder, posOrder))
-        let fileLineColumn = fun (r: range) -> r.FileName, (r.Start, r.End)
+        let fileLineColumn = fun (r: range) -> struct (r.FileName, struct (r.Start, r.End))
 
         { new IComparer<range> with
             member _.Compare(x, xx) =