Fix SignatureHash to include constant values in hash computation

.gitignore

@@ -139,6 +139,9 @@ positive.exe
 /src/FSharp.DependencyManager.Nuget/StandardError.txt
 /src/FSharp.DependencyManager.Nuget/StandardOutput.txt
 
+# Test result files
+tests/**/TestResults/*.trx
+
 # Standard output/error files in root directory
 StandardOutput.txt
 StandardError.txt

docs/release-notes/.FSharp.Compiler.Service/10.0.100.md

@@ -4,6 +4,7 @@
 
 ### Fixed
 
+* Fix SignatureHash to include constant values in hash computation ([Issue #18758](https://github.com/dotnet/fsharp/issues/18758))
 * Fix parsing errors using anonymous records and units of measures ([PR #18543](https://github.com/dotnet/fsharp/pull/18543))
 * Fix parsing errors using anonymous records and code quotations ([PR #18603](https://github.com/dotnet/fsharp/pull/18603))
 * Better error message for attribute targets. ([PR #18641](https://github.com/dotnet/fsharp/pull/18641))

src/Compiler/Utilities/TypeHashing.fs

@@ -302,6 +302,28 @@ module HashTastMemberOrVals =
 
             combinedHash
 
+    /// Hash a constant value with exhaustive pattern matching over all Const cases
+    let private hashConst (constVal: Const) : Hash =
+        match constVal with
+        | Const.Bool b -> hash b
+        | Const.SByte x -> hash x
+        | Const.Byte x -> hash x
+        | Const.Int16 x -> hash x
+        | Const.UInt16 x -> hash x
+        | Const.Int32 x -> hash x
+        | Const.UInt32 x -> hash x
+        | Const.Int64 x -> hash x
+        | Const.UInt64 x -> hash x
+        | Const.IntPtr x -> hash x
+        | Const.UIntPtr x -> hash x
+        | Const.Single x -> hash x
+        | Const.Double x -> hash x
+        | Const.Char x -> hash x
+        | Const.String x -> hashText x
+        | Const.Decimal x -> hash x
+        | Const.Unit -> 0
+        | Const.Zero -> 0
+
     let private hashNonMemberVal (g: TcGlobals, observer) (tps, v: Val, tau, cxs) =
         if HashAccessibility.isHiddenToObserver v.Accessibility observer then
             0
@@ -315,7 +337,13 @@ module HashTastMemberOrVals =
             let attribsHash = hashAttributeList v.Attribs
 
             let combinedHash = nameHash @@ typarHash @@ typeHash @@ flagsHash @@ attribsHash
-            combinedHash
+
+            // Include literal constant value in hash for deterministic builds
+            match v.LiteralValue with
+            | Some constVal ->
+                let constHash = hashConst constVal
+                combinedHash @@ constHash
+            | None -> combinedHash
 
     let hashValOrMemberNoInst (g, obs) (vref: ValRef) =
         match vref.MemberInfo with

tests/fsharp/Compiler/CodeGen/EmittedIL/DeterministicTests.fs

@@ -333,3 +333,21 @@ let inline myFunc x y = x - y"""
             Assert.Equal(mvid1,mvid2)
         else
             Assert.NotEqual(mvid1,mvid2)
+
+    [<Fact>]
+    let ``Reference assemblies MVID must change when literal constant value changes`` () =
+        let codeWithLiteral42 = """
+module TestModule
+[<Literal>]
+let X = 42
+"""
+
+        let codeWithLiteral43 = """
+module TestModule
+[<Literal>]
+let X = 43
+"""
+
+        let mvid1, mvid2 = calculateRefAssMvids codeWithLiteral42 codeWithLiteral43
+        // Different literal values should produce different MVIDs
+        Assert.NotEqual(mvid1, mvid2)