[4.2] [Diagnostics] Hint contextual type diagnostics with expression type if known

lib/Sema/CSDiag.cpp

@@ -886,7 +886,8 @@ class FailureDiagnosis :public ASTVisitor<FailureDiagnosis, /*exprresult*/bool>{
   /// Attempt to produce a diagnostic for a mismatch between an expression's
   /// type and its assumed contextual type.
   bool diagnoseContextualConversionError(Expr *expr, Type contextualType,
-                                         ContextualTypePurpose CTP);
+                                         ContextualTypePurpose CTP,
+                                         Type suggestedType = Type());
 
   /// For an expression being type checked with a CTP_CalleeResult contextual
   /// type, try to diagnose a problem.
@@ -2780,7 +2781,8 @@ static bool tryDiagnoseNonEscapingParameterToEscaping(
 }
 
 bool FailureDiagnosis::diagnoseContextualConversionError(
-    Expr *expr, Type contextualType, ContextualTypePurpose CTP) {
+    Expr *expr, Type contextualType, ContextualTypePurpose CTP,
+    Type suggestedType) {
   // If the constraint system has a contextual type, then we can test to see if
   // this is the problem that prevents us from solving the system.
   if (!contextualType) {
@@ -2799,11 +2801,16 @@ bool FailureDiagnosis::diagnoseContextualConversionError(
   if (contextualType->is<InOutType>())
     options |= TCC_AllowLValue;
 
-  auto recheckedExpr = typeCheckChildIndependently(expr, options);
+  auto *recheckedExpr = typeCheckChildIndependently(expr, options);
   auto exprType = recheckedExpr ? CS.getType(recheckedExpr) : Type();
 
+  // If there is a suggested type and re-typecheck failed, let's use it.
+  if (!exprType)
+    exprType = suggestedType;
+
   // If it failed and diagnosed something, then we're done.
-  if (!exprType) return true;
+  if (!exprType)
+    return CS.TC.Diags.hadAnyError();
 
   // If we contextually had an inout type, and got a non-lvalue result, then
   // we fail with a mutability error.
@@ -5263,7 +5270,7 @@ bool FailureDiagnosis::diagnoseTrailingClosureErrors(ApplyExpr *callExpr) {
     }
   };
 
-  SmallVector<Type, 4> possibleTypes;
+  SmallPtrSet<TypeBase *, 4> possibleTypes;
   auto currentType = CS.getType(fnExpr);
 
   // If current type has type variables or unresolved types
@@ -5283,10 +5290,10 @@ bool FailureDiagnosis::diagnoseTrailingClosureErrors(ApplyExpr *callExpr) {
       return diagnoseContextualConversionError(callExpr, contextualType,
                                                CS.getContextualTypePurpose());
   } else {
-    possibleTypes.push_back(currentType);
+    possibleTypes.insert(currentType.getPointer());
   }
 
-  for (auto type : possibleTypes) {
+  for (Type type : possibleTypes) {
     auto *fnType = type->getAs<AnyFunctionType>();
     if (!fnType)
       continue;
@@ -5377,7 +5384,7 @@ bool FailureDiagnosis::diagnoseCallContextualConversionErrors(
   auto *DC = CS.DC;
 
   auto typeCheckExpr = [](TypeChecker &TC, Expr *expr, DeclContext *DC,
-                          SmallVectorImpl<Type> &types,
+                          SmallPtrSetImpl<TypeBase *> &types,
                           Type contextualType = Type()) {
     CalleeListener listener(contextualType);
     TC.getPossibleTypesOfExpressionWithoutApplying(
@@ -5387,7 +5394,7 @@ bool FailureDiagnosis::diagnoseCallContextualConversionErrors(
   // First let's type-check expression without contextual type, and
   // see if that's going to produce a type, if so, let's type-check
   // again, this time using given contextual type.
-  SmallVector<Type, 4> withoutContextual;
+  SmallPtrSet<TypeBase *, 4> withoutContextual;
   typeCheckExpr(TC, callExpr, DC, withoutContextual);
 
   // If there are no types returned, it means that problem was
@@ -5396,12 +5403,17 @@ bool FailureDiagnosis::diagnoseCallContextualConversionErrors(
   if (withoutContextual.empty())
     return false;
 
-  SmallVector<Type, 4> withContextual;
+  SmallPtrSet<TypeBase *, 4> withContextual;
   typeCheckExpr(TC, callExpr, DC, withContextual, contextualType);
   // If type-checking with contextual type didn't produce any results
   // it means that we have a contextual mismatch.
-  if (withContextual.empty())
-    return diagnoseContextualConversionError(callExpr, contextualType, CTP);
+  if (withContextual.empty()) {
+    // If there is just a single choice, we can hit contextual diagnostics
+    // about it in case re-typecheck fails.
+    Type exprType = withoutContextual.size() == 1 ? *withoutContextual.begin() : Type();
+    return diagnoseContextualConversionError(callExpr, contextualType, CTP,
+                                             exprType);
+  }
 
   // If call produces a single type when type-checked with contextual
   // expression, it means that the problem is elsewhere, any other
@@ -5420,15 +5432,15 @@ static bool shouldTypeCheckFunctionExpr(TypeChecker &TC, DeclContext *DC,
   if (!isa<UnresolvedDotExpr>(fnExpr))
     return true;
 
-  SmallVector<Type, 4> fnTypes;
+  SmallPtrSet<TypeBase *, 4> fnTypes;
   TC.getPossibleTypesOfExpressionWithoutApplying(fnExpr, DC, fnTypes,
                                        FreeTypeVariableBinding::UnresolvedType);
 
   if (fnTypes.size() == 1) {
     // Some member types depend on the arguments to produce a result type,
     // type-checking such expressions without associated arguments is
     // going to produce unrelated diagnostics.
-    if (auto fn = fnTypes[0]->getAs<AnyFunctionType>()) {
+    if (auto fn = (*fnTypes.begin())->getAs<AnyFunctionType>()) {
       auto resultType = fn->getResult();
       if (resultType->hasUnresolvedType() || resultType->hasTypeVariable())
         return false;
@@ -5483,7 +5495,7 @@ bool FailureDiagnosis::visitApplyExpr(ApplyExpr *callExpr) {
     isa<UnresolvedDotExpr>(callExpr->getFn())) {
     fnExpr = callExpr->getFn();
 
-    SmallVector<Type, 4> types;
+    SmallPtrSet<TypeBase *, 4> types;
     CS.TC.getPossibleTypesOfExpressionWithoutApplying(fnExpr, CS.DC, types);
 
     auto isFunctionType = [getFuncType](Type type) -> bool {

lib/Sema/TypeCheckConstraints.cpp

@@ -2010,7 +2010,7 @@ getTypeOfExpressionWithoutApplying(Expr *&expr, DeclContext *dc,
 }
 
 void TypeChecker::getPossibleTypesOfExpressionWithoutApplying(
-    Expr *&expr, DeclContext *dc, SmallVectorImpl<Type> &types,
+    Expr *&expr, DeclContext *dc, SmallPtrSetImpl<TypeBase *> &types,
     FreeTypeVariableBinding allowFreeTypeVariables,
     ExprTypeCheckListener *listener) {
   PrettyStackTraceExpr stackTrace(Context, "type-checking", expr);
@@ -2044,7 +2044,7 @@ void TypeChecker::getPossibleTypesOfExpressionWithoutApplying(
   for (auto &solution : viable) {
     auto exprType = solution.simplifyType(cs.getType(expr));
     assert(exprType && !exprType->hasTypeVariable());
-    types.push_back(exprType);
+    types.insert(exprType.getPointer());
   }
 }
 

lib/Sema/TypeChecker.h

@@ -1745,7 +1745,7 @@ class TypeChecker final : public LazyResolver {
       ExprTypeCheckListener *listener = nullptr);
 
   void getPossibleTypesOfExpressionWithoutApplying(
-      Expr *&expr, DeclContext *dc, SmallVectorImpl<Type> &types,
+      Expr *&expr, DeclContext *dc, SmallPtrSetImpl<TypeBase *> &types,
       FreeTypeVariableBinding allowFreeTypeVariables =
           FreeTypeVariableBinding::Disallow,
       ExprTypeCheckListener *listener = nullptr);

test/Constraints/diagnostics.swift

@@ -501,7 +501,7 @@ func r21684487() {
   var closures = Array<MyClosure>()
   let testClosure = {(list: [Int]) -> Bool in return true}
 
-  let closureIndex = closures.index{$0 === testClosure} // expected-error {{cannot check reference equality of functions; operands here have types '_' and '([Int]) -> Bool'}}
+  let closureIndex = closures.index{$0 === testClosure} // expected-error {{cannot check reference equality of functions;}}
 }
 
 // <rdar://problem/18397777> QoI: special case comparisons with nil

test/Constraints/rdar40002266.swift

@@ -0,0 +1,11 @@
+// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -typecheck -verify %s
+// REQUIRES: objc_interop
+
+import Foundation
+
+struct S {
+  init<T: NSNumber>(_ num: T) {
+    self.init(num != 0) // expected-error {{binary operator '!=' cannot be applied to operands of type 'T' and 'Int'}}
+    // expected-note@-1 {{expected an argument list of type '(Int, Int)'}}
+  }
+}