Fix for missing IntelliSense after type constraint error

src/fsharp/TypeChecker.fs

@@ -3906,7 +3906,7 @@ type DelayedItem =
 
   /// DelayedApp (isAtomic, argExpr, mFuncAndArg) 
   ///
-  /// Represents the args in "item args", or "item.[args]". 
+  /// Represents the args in "item args", or "item.[args]".
   | DelayedApp of ExprAtomicFlag * Ast.SynExpr * range
 
   /// Represents the long identifiers in "item.Ident1", or "item.Ident1.Ident2" etc.
@@ -5323,7 +5323,15 @@ and RecordNameAndTypeResolutions_IdeallyWithoutHavingOtherEffects_Delayed cenv e
             RecordNameAndTypeResolutions_IdeallyWithoutHavingOtherEffects cenv env tpenv arg
             dummyCheckedDelayed otherDelayed
         | _ -> ()
-    dummyCheckedDelayed delayed 
+    dummyCheckedDelayed delayed
+
+// Calls UnifyTypes, but upon error only does the minimal error recovery
+// so that IntelliSense information can continue to be collected.
+and UnifyTypesAndRecover cenv env m expectedTy actualTy =
+    try
+        UnifyTypes cenv env m expectedTy actualTy
+    with e ->
+        errorRecovery e m
 
 and TcExprOfUnknownType cenv env tpenv expr =
     let exprty = NewInferenceType ()
@@ -8089,7 +8097,7 @@ and PropagateThenTcDelayed cenv overallTy env tpenv mExpr expr exprty (atomicFla
         | [] -> 
             // Avoid unifying twice: we're about to unify in TcDelayed 
             if not (isNil delayed) then 
-                UnifyTypes cenv env mExpr overallTy exprty
+                UnifyTypesAndRecover cenv env mExpr overallTy exprty
         | DelayedDot :: _
         | DelayedSet _ :: _
         | DelayedDotLookup _ :: _ -> ()
@@ -8108,7 +8116,7 @@ and PropagateThenTcDelayed cenv overallTy env tpenv mExpr expr exprty (atomicFla
                 | SynExpr.CompExpr _ -> ()
                 | _ -> 
                     // 'delayed' is about to be dropped on the floor, first do rudimentary checking to get name resolutions in its body
-                    RecordNameAndTypeResolutions_IdeallyWithoutHavingOtherEffects_Delayed cenv env tpenv delayed 
+                    RecordNameAndTypeResolutions_IdeallyWithoutHavingOtherEffects_Delayed cenv env tpenv delayed
                     error (NotAFunction(denv,overallTy,mExpr,mArg)) 
 
     propagate delayed expr.Range exprty
@@ -8127,7 +8135,8 @@ and TcDelayed cenv overallTy env tpenv mExpr expr exprty (atomicFlag:ExprAtomicF
     match delayed with 
     | []  
     | DelayedDot :: _ -> 
-        UnifyTypes cenv env mExpr overallTy exprty; expr.Expr,tpenv
+        UnifyTypesAndRecover cenv env mExpr overallTy exprty
+        expr.Expr,tpenv
     // expr.M(args) where x.M is a .NET method or index property 
     // expr.M<tyargs>(args) where x.M is a .NET method or index property 
     // expr.M where x.M is a .NET method or index property 
@@ -8689,7 +8698,7 @@ and TcItemThen cenv overallTy env tpenv (item,mItem,rest,afterOverloadResolution
 
     | Item.CustomOperation (nm,usageTextOpt,_) -> 
         // 'delayed' is about to be dropped on the floor, first do rudimentary checking to get name resolutions in its body 
-        RecordNameAndTypeResolutions_IdeallyWithoutHavingOtherEffects_Delayed cenv env tpenv delayed 
+        RecordNameAndTypeResolutions_IdeallyWithoutHavingOtherEffects_Delayed cenv env tpenv delayed
         match usageTextOpt() with
         | None -> error(Error(FSComp.SR.tcCustomOperationNotUsedCorrectly(nm), mItem))
         | Some usageText -> error(Error(FSComp.SR.tcCustomOperationNotUsedCorrectly2(nm,usageText), mItem))

tests/fsharp/typeProviders/negTests/neg1.bsl

@@ -1966,16 +1966,22 @@ neg1.fsx(438,109,438,110): typecheck error FS0001: This expression was expected
 but here has type
     'string'    
 
+neg1.fsx(438,9,438,111): typecheck error FS3033: The type provider 'Provider.GoodProviderForNegativeStaticParameterTypeTests' reported an error: Specified cast is not valid.
+
 neg1.fsx(440,119,440,120): typecheck error FS0001: This expression was expected to have type
     'int'    
 but here has type
     'string'    
 
+neg1.fsx(440,19,440,121): typecheck error FS3033: The type provider 'Provider.GoodProviderForNegativeStaticParameterTypeTests' reported an error: Specified cast is not valid.
+
 neg1.fsx(440,119,440,120): typecheck error FS0001: This expression was expected to have type
     'int'    
 but here has type
     'string'    
 
+neg1.fsx(440,19,440,121): typecheck error FS3033: The type provider 'Provider.GoodProviderForNegativeStaticParameterTypeTests' reported an error: Specified cast is not valid.
+
 neg1.fsx(448,9,448,107): typecheck error FS3148: Too many static parameters. Expected at most 1 parameters, but got 2 unnamed and 0 named parameters.
 
 neg1.fsx(449,105,449,110): typecheck error FS3083: The static parameter 'Count' has already been given a value

tests/fsharp/typecheck/sigs/neg04.bsl

@@ -31,6 +31,14 @@ but given a
     ''g list -> 'h'    
 The type 'seq<'a>' does not match the type ''f list'
 
+neg04.fs(47,49,47,51): typecheck error FS0784: This numeric literal requires that a module 'NumericLiteralN' defining functions FromZero, FromOne, FromInt32, FromInt64 and FromString be in scope
+
+neg04.fs(47,30,47,51): typecheck error FS0001: Type mismatch. Expecting a
+    'seq<'a> -> 'f'    
+but given a
+    ''g list -> 'h'    
+The type 'seq<'a>' does not match the type ''f list'
+
 neg04.fs(61,25,61,40): typecheck error FS0001: This expression was expected to have type
     'ClassType1'    
 but here has type

tests/fsharp/typecheck/sigs/neg20.bsl

@@ -245,6 +245,16 @@ neg20.fs(184,28,184,33): typecheck error FS0001: This expression was expected to
 but here has type
     'obj'    
 
+neg20.fs(184,28,184,33): typecheck error FS0001: This expression was expected to have type
+    'int'    
+but here has type
+    'obj'    
+
+neg20.fs(184,34,184,39): typecheck error FS0001: This expression was expected to have type
+    'int'    
+but here has type
+    'obj'    
+
 neg20.fs(184,34,184,39): typecheck error FS0001: This expression was expected to have type
     'int'    
 but here has type
@@ -272,6 +282,16 @@ neg20.fs(190,28,190,33): typecheck error FS0001: This expression was expected to
 but here has type
     'obj'    
 
+neg20.fs(190,28,190,33): typecheck error FS0001: This expression was expected to have type
+    'string'    
+but here has type
+    'obj'    
+
+neg20.fs(190,34,190,39): typecheck error FS0001: This expression was expected to have type
+    'string'    
+but here has type
+    'obj'    
+
 neg20.fs(190,34,190,39): typecheck error FS0001: This expression was expected to have type
     'string'    
 but here has type

tests/fsharp/typecheck/sigs/neg22.bsl

@@ -21,6 +21,18 @@ but given a
     'float<kg>'    
 The unit of measure 'm' does not match the unit of measure 'kg'
 
+neg22.fs(17,22,17,29): typecheck error FS0001: Type mismatch. Expecting a
+    'float<m>'    
+but given a
+    'float<kg>'    
+The unit of measure 'm' does not match the unit of measure 'kg'
+
+neg22.fs(17,20,17,29): typecheck error FS0001: Type mismatch. Expecting a
+    'float<m>'    
+but given a
+    'float<kg>'    
+The unit of measure 'm' does not match the unit of measure 'kg'
+
 neg22.fs(28,12,28,18): typecheck error FS0957: The declared type parameters for this type extension do not match the declared type parameters on the original type 'LibGen<_>'
 
 neg22.fs(40,12,40,18): typecheck error FS0957: The declared type parameters for this type extension do not match the declared type parameters on the original type 'LibGen<_>'