Checker: recover on checking language version

docs/release-notes/.FSharp.Compiler.Service/11.0.100.md

@@ -95,6 +95,7 @@
 * Debug: rework for expressions stepping ([PR #19894](https://github.com/dotnet/fsharp/pull/19894))
 * Debug: rework conditional erasure, fix stepping over literals ([PR #19897](https://github.com/dotnet/fsharp/pull/19897))
 * Debug: fix if and match condition sequence points ([PR #19932](https://github.com/dotnet/fsharp/pull/19932))
+* Checker: recover on checking language version ([PR ##19970](https://github.com/dotnet/fsharp/pull/19970))
 
 ### Changed
 

src/Compiler/Checking/CheckDeclarations.fs

@@ -751,7 +751,7 @@ let TcOpenModuleOrNamespaceDecl tcSink g amap scopem env (longId, m) =
 let TcOpenTypeDecl (cenv: cenv) mOpenDecl scopem env (synType: SynType, m) =
     let g = cenv.g
 
-    checkLanguageFeatureError g.langVersion LanguageFeature.OpenTypeDeclaration mOpenDecl
+    checkLanguageFeatureAndRecover g.langVersion LanguageFeature.OpenTypeDeclaration mOpenDecl
 
     let ty, _tpenv = TcType cenv NoNewTypars CheckCxs ItemOccurrence.Open WarnOnIWSAM.Yes env emptyUnscopedTyparEnv synType
 

src/Compiler/Checking/CheckFormatStrings.fs

@@ -396,7 +396,7 @@ let parseFormatStringInternal
             let ch = fmt[i]
             match ch with
             | 'd' | 'i' | 'u' | 'B' | 'o' | 'x' | 'X' ->
-                if ch = 'B' then checkLanguageFeatureError g.langVersion Features.LanguageFeature.PrintfBinaryFormat m
+                if ch = 'B' then checkLanguageFeatureAndRecover g.langVersion Features.LanguageFeature.PrintfBinaryFormat m
                 if info.precision then failwith (FSComp.SR.forFormatDoesntSupportPrecision(ch.ToString()))
                 collectSpecifierLocation fragLine fragCol 1
                 let i = skipPossibleInterpolationHole (i+1)

src/Compiler/Checking/CheckPatterns.fs

@@ -286,7 +286,7 @@ and TcPat warnOnUpper (cenv: cenv) env valReprInfo vFlags (patEnv: TcPatLinearEn
 
     match synPat with
     | SynPat.As (_, SynPat.Named _, _) -> ()
-    | SynPat.As (_, _, m) -> checkLanguageFeatureError g.langVersion LanguageFeature.NonVariablePatternsToRightOfAsPatterns m
+    | SynPat.As (_, _, m) -> checkLanguageFeatureAndRecover g.langVersion LanguageFeature.NonVariablePatternsToRightOfAsPatterns m
     | _ -> ()
 
     match synPat with

src/Compiler/Checking/Expressions/CheckExpressions.fs

@@ -5391,7 +5391,7 @@ and TcPatLongIdentActivePatternCase warnOnUpper (cenv: cenv) (env: TcEnv) vFlags
 
         // partial active pattern (returning bool) doesn't have output arg
         if (not apinfo.IsTotal && isBoolTy g retTy) then
-            checkLanguageFeatureError g.langVersion LanguageFeature.BooleanReturningAndReturnTypeDirectedPartialActivePattern m
+            checkLanguageFeatureAndRecover g.langVersion LanguageFeature.BooleanReturningAndReturnTypeDirectedPartialActivePattern m
             if paramCount = List.length args then
                 args, SynPat.Const(SynConst.Unit, m)
             else
@@ -5946,7 +5946,7 @@ and TcExprUndelayed (cenv: cenv) (overallTy: OverallTy) env tpenv (synExpr: SynE
 
     | SynExpr.InterpolatedString (parts, _, m) ->
         TcNonControlFlowExpr env <| fun env ->
-        checkLanguageFeatureError g.langVersion LanguageFeature.StringInterpolation m
+        checkLanguageFeatureAndRecover g.langVersion LanguageFeature.StringInterpolation m
         CallExprHasTypeSink cenv.tcSink (m, env.NameEnv, overallTy.Commit, env.AccessRights)
         TcInterpolatedStringExpr cenv overallTy env m tpenv parts
 
@@ -11438,11 +11438,11 @@ and TcNormalizedBinding declKind (cenv: cenv) env tpenv overallTy safeThisValOpt
 
             match apRetTy with
             | ActivePatternReturnKind.Boolean ->
-                checkLanguageFeatureError g.langVersion LanguageFeature.BooleanReturningAndReturnTypeDirectedPartialActivePattern mBinding
+                checkLanguageFeatureAndRecover g.langVersion LanguageFeature.BooleanReturningAndReturnTypeDirectedPartialActivePattern mBinding
             | ActivePatternReturnKind.StructTypeWrapper when not isStructRetTy ->
-                checkLanguageFeatureError g.langVersion LanguageFeature.BooleanReturningAndReturnTypeDirectedPartialActivePattern mBinding
+                checkLanguageFeatureAndRecover g.langVersion LanguageFeature.BooleanReturningAndReturnTypeDirectedPartialActivePattern mBinding
             | ActivePatternReturnKind.StructTypeWrapper ->
-                checkLanguageFeatureError g.langVersion LanguageFeature.StructActivePattern mBinding
+                checkLanguageFeatureAndRecover g.langVersion LanguageFeature.StructActivePattern mBinding
             | ActivePatternReturnKind.RefTypeWrapper -> ()
 
             UnifyTypes cenv env mBinding (apinfo.ResultType g m activePatResTys apRetTy) apReturnTy
@@ -11933,7 +11933,7 @@ and TcLetBinding (cenv: cenv) isUse env containerInfo declKind tpenv (synBinds,
                     if not isDiscarded then
                         errorR(Error(FSComp.SR.tcInvalidUseBinding(), m))
                     else
-                        checkLanguageFeatureError g.langVersion LanguageFeature.UseBindingValueDiscard checkedPat.Range
+                        checkLanguageFeatureAndRecover g.langVersion LanguageFeature.UseBindingValueDiscard checkedPat.Range
 
                 elif isFixed then
                     errorR(Error(FSComp.SR.tcInvalidUseBinding(), m))
@@ -12287,7 +12287,7 @@ and CheckForNonAbstractInterface (g: TcGlobals) declKind tcref (memberFlags: Syn
             if not isMemberStatic then
                 error(Error(FSComp.SR.tcConcreteMembersIllegalInInterface(), m))
             else
-                checkLanguageFeatureError g.langVersion LanguageFeature.StaticMembersInInterfaces m
+                checkLanguageFeatureAndRecover g.langVersion LanguageFeature.StaticMembersInInterfaces m
 
 //-------------------------------------------------------------------------
 // TcLetrecBindings - AnalyzeAndMakeAndPublishRecursiveValue s

tests/FSharp.Compiler.ComponentTests/Language/BooleanReturningAndReturnTypeDirectedPartialActivePatternTests.fs

@@ -100,3 +100,22 @@ match "A" with
    Result")
         (Error 3868, Line 13, Col 3, Line 13, Col 30, "This active pattern does not expect any arguments, i.e., it should be used like 'IsA' instead of 'IsA x'.")
     ]
+
+[<Fact>]
+let ``Language version check`` () =
+    FSharp """
+let (|LessThan|_|) (other: int) x = x <= other
+
+match 1 with
+| LessThan "" -> UnresolvedName
+| _ -> ()
+"""
+    |> withLangVersion80
+    |> typecheck
+    |> shouldFail
+    |> withDiagnostics [
+        Error 3350, Line 2, Col 6, Line 2, Col 18, "Feature 'Boolean-returning and return-type-directed partial active patterns' is not available in F# 8.0. Please use language version 9.0 or greater."
+        Error 3350, Line 5, Col 3, Line 5, Col 14, "Feature 'Boolean-returning and return-type-directed partial active patterns' is not available in F# 8.0. Please use language version 9.0 or greater."
+        Error 1, Line 5, Col 12, Line 5, Col 14, "This expression was expected to have type\n        'int' \n        but here has type\n        'string' "
+        Error 39, Line 5, Col 18, Line 5, Col 32, "The value or constructor 'UnresolvedName' is not defined."
+    ]