Add MethodOverloadsCache language feature (preview only)

Copilot · T-Gro · Copilot · commit 6333f4971f06 · 2026-02-11T21:39:20.000Z
Co-authored-by: T-Gro &lt;46543583+T-Gro@users.noreply.github.com&gt;
diff --git a/src/Compiler/Checking/ConstraintSolver.fs b/src/Compiler/Checking/ConstraintSolver.fs
@@ -3644,11 +3644,13 @@ and ResolveOverloading
 
           // Try to use cached overload resolution result for repetitive patterns
           // Only cache when:
+          // - Language feature is enabled
           // - NOT doing op_Explicit/op_Implicit conversions
           // - NOT doing trait constraint (SRTP) resolution (cx is None)
           // - Have multiple candidates
           let cacheKeyOpt = 
-              if not isOpConversion && cx.IsNone && candidates.Length > 1 then
+              if g.langVersion.SupportsFeature LanguageFeature.MethodOverloadsCache && 
+                 not isOpConversion && cx.IsNone && candidates.Length > 1 then
                   tryComputeOverloadCacheKey g calledMethGroup callerArgs reqdRetTyOpt
               else
                   ValueNone
diff --git a/src/Compiler/Checking/OverloadResolutionCache.fs b/src/Compiler/Checking/OverloadResolutionCache.fs
@@ -237,25 +237,29 @@ let storeCacheResult
     (anyHasOutArgs: bool)
     (calledMethOpt: CalledMeth<'T> voption)
     =
-    match cacheKeyOpt with
-    | ValueSome cacheKey ->
-        match computeCacheResult calledMethGroup calledMethOpt with
-        | Some res ->
-            // Store under the "before" key
-            cache.TryAdd(cacheKey, res) |> ignore
-
-            // Compute "after" key - types may have been solved during resolution
-            // If different from "before" key, store under that too for future hits
-            match tryComputeOverloadCacheKey g calledMethGroup callerArgs reqdRetTyOpt anyHasOutArgs with
-            | ValueSome afterKey when afterKey <> cacheKey -> cache.TryAdd(afterKey, res) |> ignore
-            | _ -> ()
-        | None -> ()
-    | ValueNone ->
-        // Even if we couldn't compute a "before" key (unstable types),
-        // try to compute an "after" key now that types may be solved
-        match tryComputeOverloadCacheKey g calledMethGroup callerArgs reqdRetTyOpt anyHasOutArgs with
-        | ValueSome afterKey ->
+    // Only store in cache if the language feature is enabled
+    if not (g.langVersion.SupportsFeature LanguageFeature.MethodOverloadsCache) then
+        ()
+    else
+        match cacheKeyOpt with
+        | ValueSome cacheKey ->
             match computeCacheResult calledMethGroup calledMethOpt with
-            | Some res -> cache.TryAdd(afterKey, res) |> ignore
+            | Some res ->
+                // Store under the "before" key
+                cache.TryAdd(cacheKey, res) |> ignore
+
+                // Compute "after" key - types may have been solved during resolution
+                // If different from "before" key, store under that too for future hits
+                match tryComputeOverloadCacheKey g calledMethGroup callerArgs reqdRetTyOpt anyHasOutArgs with
+                | ValueSome afterKey when afterKey <> cacheKey -> cache.TryAdd(afterKey, res) |> ignore
+                | _ -> ()
             | None -> ()
-        | ValueNone -> ()
+        | ValueNone ->
+            // Even if we couldn't compute a "before" key (unstable types),
+            // try to compute an "after" key now that types may be solved
+            match tryComputeOverloadCacheKey g calledMethGroup callerArgs reqdRetTyOpt anyHasOutArgs with
+            | ValueSome afterKey ->
+                match computeCacheResult calledMethGroup calledMethOpt with
+                | Some res -> cache.TryAdd(afterKey, res) |> ignore
+                | None -> ()
+            | ValueNone -> ()
diff --git a/src/Compiler/FSComp.txt b/src/Compiler/FSComp.txt
@@ -1803,5 +1803,6 @@ featureAllowLetOrUseBangTypeAnnotationWithoutParens,"Allow let! and use! type an
 3878,tcAttributeIsNotValidForUnionCaseWithFields,"This attribute is not valid for use on union cases with fields."
 3879,xmlDocNotFirstOnLine,"XML documentation comments should be the first non-whitespace text on a line."
 featureReturnFromFinal,"Support for ReturnFromFinal/YieldFromFinal in computation expressions to enable tailcall optimization when available on the builder."
+featureMethodOverloadsCache,"Support for caching method overload resolution results for improved compilation performance."
 3880,optsLangVersionOutOfSupport,"Language version '%s' is out of support. The last .NET SDK supporting it is available at https://dotnet.microsoft.com/en-us/download/dotnet/%s"
 3881,optsUnrecognizedLanguageFeature,"Unrecognized language feature name: '%s'. Use a valid feature name such as 'NameOf' or 'StringInterpolation'."
diff --git a/src/Compiler/Facilities/LanguageFeatures.fs b/src/Compiler/Facilities/LanguageFeatures.fs
@@ -104,6 +104,7 @@ type LanguageFeature =
     | ErrorOnInvalidDeclsInTypeDefinitions
     | AllowTypedLetUseAndBang
     | ReturnFromFinal
+    | MethodOverloadsCache
 
 /// LanguageVersion management
 type LanguageVersion(versionText, ?disabledFeaturesArray: LanguageFeature array) =
@@ -251,6 +252,7 @@ type LanguageVersion(versionText, ?disabledFeaturesArray: LanguageFeature array)
 
                 // F# preview (still preview in 10.0)
                 LanguageFeature.FromEndSlicing, previewVersion // Unfinished features --- needs work
+                LanguageFeature.MethodOverloadsCache, previewVersion // Performance optimization for overload resolution
             ]
 
     static let defaultLanguageVersion = LanguageVersion("default")
@@ -440,6 +442,7 @@ type LanguageVersion(versionText, ?disabledFeaturesArray: LanguageFeature array)
         | LanguageFeature.ErrorOnInvalidDeclsInTypeDefinitions -> FSComp.SR.featureErrorOnInvalidDeclsInTypeDefinitions ()
         | LanguageFeature.AllowTypedLetUseAndBang -> FSComp.SR.featureAllowLetOrUseBangTypeAnnotationWithoutParens ()
         | LanguageFeature.ReturnFromFinal -> FSComp.SR.featureReturnFromFinal ()
+        | LanguageFeature.MethodOverloadsCache -> FSComp.SR.featureMethodOverloadsCache ()
 
     /// Get a version string associated with the given feature.
     static member GetFeatureVersionString feature =
diff --git a/src/Compiler/Facilities/LanguageFeatures.fsi b/src/Compiler/Facilities/LanguageFeatures.fsi
@@ -95,6 +95,7 @@ type LanguageFeature =
     | ErrorOnInvalidDeclsInTypeDefinitions
     | AllowTypedLetUseAndBang
     | ReturnFromFinal
+    | MethodOverloadsCache
 
 /// LanguageVersion management
 type LanguageVersion =
