Type checker: recover on checking binding parameter contraints

Author: auduchinok

src/Compiler/Checking/Expressions/CheckExpressions.fs

@@ -11561,12 +11561,14 @@ and TcLetBinding (cenv: cenv) isUse env containerInfo declKind tpenv (synBinds,
 
     // Canonicalize constraints prior to generalization
     let denv = env.DisplayEnv
-    CanonicalizePartialInferenceProblem cenv.css denv synBindsRange
-        (checkedBinds |> List.collect (fun tbinfo ->
-            let (CheckedBindingInfo(_, _, _, _, explicitTyparInfo, _, _, _, tauTy, _, _, _, _, _)) = tbinfo
-            let (ExplicitTyparInfo(_, declaredTypars, _)) = explicitTyparInfo
-            let maxInferredTypars = (freeInTypeLeftToRight g false tauTy)
-            declaredTypars @ maxInferredTypars))
+    try
+        CanonicalizePartialInferenceProblem cenv.css denv synBindsRange
+            (checkedBinds |> List.collect (fun tbinfo ->
+                let (CheckedBindingInfo(_, _, _, _, explicitTyparInfo, _, _, _, tauTy, _, _, _, _, _)) = tbinfo
+                let (ExplicitTyparInfo(_, declaredTypars, _)) = explicitTyparInfo
+                let maxInferredTypars = (freeInTypeLeftToRight g false tauTy)
+                declaredTypars @ maxInferredTypars))
+    with RecoverableException _ -> ()
 
     let lazyFreeInEnv = lazy (GeneralizationHelpers.ComputeUngeneralizableTypars env)
 

tests/FSharp.Compiler.Service.Tests/TypeChecker/TypeCheckerRecoveryTests.fs

@@ -1,9 +1,20 @@
 module FSharp.Compiler.Service.Tests.TypeChecker.TypeCheckerRecoveryTests
 
 open FSharp.Compiler.Service.Tests
+open FSharp.Compiler.Text
 open FSharp.Test.Assert
 open Xunit
 
+let assertHasSymbolUsageAtCaret name source =
+    let context, checkResults = Checker.getCheckedResolveContext source
+
+    getSymbolUses checkResults
+    |> Seq.exists (fun symbolUse ->
+        Range.rangeContainsPos symbolUse.Range context.Pos &&
+        symbolUse.Symbol.DisplayNameCore = name
+    )
+    |> shouldEqual true
+
 [<Fact>]
 let ``Let 01`` () =
     let _, checkResults = getParseAndCheckResults """
@@ -49,4 +60,24 @@ Math.Max(a,b,)
         "(4,0--4,14)", 503
     ]
 
-    assertHasSymbolUsages ["Max"] checkResults
+    assertHasSymbolUsages ["Max"] checkResults
+
+module Constraints =
+    [<Fact>]
+    let ``Type 01`` () =
+        assertHasSymbolUsageAtCaret "f" """
+let f (x: string) =
+    x + 1
+
+{caret}f ""
+"""
+
+    [<Fact>]
+    let ``Type 02`` () =
+        assertHasSymbolUsageAtCaret "M" """
+type T =
+    static member M(x: string) =
+        x + 1
+
+T.M{caret} ""
+"""