[6.2][Diagnostics] A collection of diagnostic fixes/improvements

include/swift/Sema/CSFix.h

@@ -560,6 +560,11 @@ class ConstraintFix {
     return false;
   }
 
+  template <typename E>
+  bool directlyAt() const {
+    return getLocator()->directlyAt<E>();
+  }
+
   void print(llvm::raw_ostream &Out) const;
 
   SWIFT_DEBUG_DUMP;

include/swift/Sema/ConstraintSystem.h

@@ -3484,6 +3484,15 @@ class ConstraintSystem {
     return nullptr;
   }
 
+  Expr *getSemanticsProvidingParentExpr(Expr *expr) {
+    while (auto *parent = getParentExpr(expr)) {
+      if (parent->getSemanticsProvidingExpr() == parent)
+        return parent;
+      expr = parent;
+    }
+    return nullptr;
+  }
+
   /// Retrieve the depth of the given expression.
   std::optional<unsigned> getExprDepth(Expr *expr) {
     if (auto result = getExprDepthAndParent(expr))

lib/Sema/CSDiagnostics.cpp

@@ -1114,7 +1114,12 @@ bool GenericArgumentsMismatchFailure::diagnoseAsError() {
   if (!diagnostic)
     return false;
 
-  emitDiagnosticAt(::getLoc(anchor), *diagnostic, fromType, toType);
+  {
+    auto diag =
+        emitDiagnosticAt(::getLoc(anchor), *diagnostic, fromType, toType);
+    (void)tryFixIts(diag);
+  }
+
   emitNotesForMismatches();
   return true;
 }

lib/Sema/CSSimplify.cpp

@@ -4039,6 +4039,12 @@ ConstraintSystem::matchDeepEqualityTypes(Type type1, Type type2,
       getConstraintLocator(locator, {LocatorPathElt::GenericType(type1),
           LocatorPathElt::GenericType(type2)});
 
+    // Optionals have a lot of special diagnostics and only one
+    // generic argument so if we're dealing with one, let's allow
+    // `repairFailures` to take care of it.
+    if (bound1->getDecl()->isOptionalDecl())
+      return matchDeepTypeArguments(*this, subflags, args1, args2, baseLoc);
+
     auto argMatchingFlags = subflags;
     // Allow the solver to produce separate fixes while matching
     // key path's root/value to a contextual type instead of the
@@ -4049,13 +4055,6 @@ ConstraintSystem::matchDeepEqualityTypes(Type type1, Type type2,
       argMatchingFlags |= TMF_MatchingGenericArguments;
     }
 
-    // Optionals have a lot of special diagnostics and only one
-    // generic argument so if we' re dealing with one, don't produce generic
-    // arguments mismatch fixes.
-    if (bound1->getDecl()->isOptionalDecl())
-      return matchDeepTypeArguments(*this, argMatchingFlags, args1, args2,
-                                    baseLoc);
-
     SmallVector<unsigned, 4> mismatches;
     auto result = matchDeepTypeArguments(
         *this, argMatchingFlags, args1, args2, baseLoc,
@@ -4282,7 +4281,8 @@ ConstraintSystem::matchExistentialTypes(Type type1, Type type2,
         if (!path.empty()) {
           auto last = path.back();
 
-          if (last.is<LocatorPathElt::ApplyArgToParam>()) {
+          if (last.is<LocatorPathElt::ApplyArgToParam>() ||
+              last.is<LocatorPathElt::AutoclosureResult>()) {
             auto proto = protoDecl->getDeclaredInterfaceType();
             // Impact is 2 here because there are two failures
             // 1 - missing conformance and 2 - incorrect argument type.
@@ -4310,6 +4310,15 @@ ConstraintSystem::matchExistentialTypes(Type type1, Type type2,
             break;
           }
 
+          if ((isExpr<ArrayExpr>(anchor) || isExpr<DictionaryExpr>(anchor)) &&
+              last.is<LocatorPathElt::TupleElement>()) {
+            auto *fix = CollectionElementContextualMismatch::create(
+                *this, type1, type2, getConstraintLocator(anchor, path));
+            if (recordFix(fix, /*impact=*/2))
+              return getTypeMatchFailure(locator);
+            break;
+          }
+
           // TODO(diagnostics): If there are any requirement failures associated
           // with result types which are part of a function type conversion,
           // let's record general conversion mismatch in order for it to capture
@@ -4979,8 +4988,18 @@ repairViaOptionalUnwrap(ConstraintSystem &cs, Type fromType, Type toType,
 
     // First, let's check whether it has been determined that
     // it was incorrect to use `?` in this position.
-    if (cs.hasFixFor(cs.getConstraintLocator(subExpr), FixKind::RemoveUnwrap))
+    if (cs.hasFixFor(cs.getConstraintLocator(subExpr), FixKind::RemoveUnwrap)) {
+      if (auto *typeVar =
+              fromType->getOptionalObjectType()->getAs<TypeVariableType>()) {
+        // If the optional chain is invalid let's unwrap optional and
+        // re-introduce the constraint to be solved later once both sides
+        // are sufficiently resolved, this would allow to diagnose not only
+        // the invalid unwrap but an invalid conversion (if any) as well.
+        cs.addConstraint(matchKind, typeVar, toType,
+                         cs.getConstraintLocator(locator));
+      }
       return true;
+    }
 
     auto type = cs.getType(subExpr);
     // If the type of sub-expression is optional, type of the
@@ -5775,6 +5794,41 @@ bool ConstraintSystem::repairFailures(
         break;
       }
 
+      // There is no subtyping between object types of inout argument/parameter.
+      if (auto argConv = path.back().getAs<LocatorPathElt::ApplyArgToParam>()) {
+        // Attempt conversions first.
+        if (hasAnyRestriction())
+          break;
+
+        // Unwraps are allowed to preserve l-valueness so we can suggest
+        // them here.
+        if (repairViaOptionalUnwrap(*this, lhs, rhs, matchKind,
+                                    conversionsOrFixes, locator))
+          return true;
+
+        auto *loc = getConstraintLocator(locator);
+
+        auto result = matchTypes(lhs, rhs, ConstraintKind::Conversion,
+                                 TMF_ApplyingFix, locator);
+
+        ConstraintFix *fix = nullptr;
+        if (result.isFailure()) {
+          // If this is a "destination" argument to a mutating operator
+          // like `+=`, let's consider it contextual and only attempt
+          // to fix type mismatch on the "source" right-hand side of
+          // such operators.
+          if (isOperatorArgument(loc) && argConv->getArgIdx() == 0)
+            break;
+
+          fix = AllowArgumentMismatch::create(*this, lhs, rhs, loc);
+        } else {
+          fix = AllowInOutConversion::create(*this, lhs, rhs, loc);
+        }
+
+        conversionsOrFixes.push_back(fix);
+        break;
+      }
+
       // If this is a problem with result type of a subscript setter,
       // let's re-attempt to repair without l-value conversion in the
       // locator to fix underlying type mismatch.
@@ -5794,7 +5848,7 @@ bool ConstraintSystem::repairFailures(
         break;
     }
 
-    LLVM_FALLTHROUGH;
+    break;
   }
 
   case ConstraintLocator::ApplyArgToParam: {
@@ -5874,52 +5928,6 @@ bool ConstraintSystem::repairFailures(
     if (repairByTreatingRValueAsLValue(lhs, rhs))
       break;
 
-    // If the problem is related to missing unwrap, there is a special
-    // fix for that.
-    if (lhs->getOptionalObjectType() && !rhs->getOptionalObjectType()) {
-      // If this is an attempt to check whether optional conforms to a
-      // particular protocol, let's do that before attempting to force
-      // unwrap the optional.
-      if (hasConversionOrRestriction(ConversionRestrictionKind::Existential))
-        break;
-
-      auto result = matchTypes(lhs->getOptionalObjectType(), rhs, matchKind,
-                               TMF_ApplyingFix, locator);
-
-      if (result.isSuccess()) {
-        conversionsOrFixes.push_back(
-            ForceOptional::create(*this, lhs, rhs, loc));
-        break;
-      }
-    }
-
-    // There is no subtyping between object types of inout argument/parameter.
-    if (elt.getKind() == ConstraintLocator::LValueConversion) {
-      auto result = matchTypes(lhs, rhs, ConstraintKind::Conversion,
-                               TMF_ApplyingFix, locator);
-
-      ConstraintFix *fix = nullptr;
-      if (result.isFailure()) {
-        // If this is a "destination" argument to a mutating operator
-        // like `+=`, let's consider it contextual and only attempt
-        // to fix type mismatch on the "source" right-hand side of
-        // such operators.
-        if (isOperatorArgument(loc) &&
-            loc->findLast<LocatorPathElt::ApplyArgToParam>()->getArgIdx() == 0)
-          break;
-
-        fix = AllowArgumentMismatch::create(*this, lhs, rhs, loc);
-      } else {
-        fix = AllowInOutConversion::create(*this, lhs, rhs, loc);
-      }
-
-      conversionsOrFixes.push_back(fix);
-      break;
-    }
-
-    if (elt.getKind() != ConstraintLocator::ApplyArgToParam)
-      break;
-
     // If argument in l-value type and parameter is `inout` or a pointer,
     // let's see if it's generic parameter matches and suggest adding explicit
     // `&`.
@@ -6046,7 +6054,7 @@ bool ConstraintSystem::repairFailures(
 
     if (repairViaOptionalUnwrap(*this, lhs, rhs, matchKind, conversionsOrFixes,
                                 locator))
-      break;
+      return true;
 
     {
       auto *calleeLocator = getCalleeLocator(loc);
@@ -6856,9 +6864,28 @@ bool ConstraintSystem::repairFailures(
     if (!path.empty() && path.back().is<LocatorPathElt::PackElement>())
       path.pop_back();
 
-    if (!path.empty() && path.back().is<LocatorPathElt::AnyRequirement>()) {
-      return repairFailures(lhs, rhs, matchKind, flags, conversionsOrFixes,
-                            getConstraintLocator(anchor, path));
+    if (!path.empty()) {
+      if (path.back().is<LocatorPathElt::AnyRequirement>()) {
+        return repairFailures(lhs, rhs, matchKind, flags, conversionsOrFixes,
+                              getConstraintLocator(anchor, path));
+      }
+
+      if (auto argConv = path.back().getAs<LocatorPathElt::ApplyArgToParam>()) {
+        auto argIdx = argConv->getArgIdx();
+        auto paramIdx = argConv->getParamIdx();
+
+        auto *argLoc = getConstraintLocator(anchor, path);
+        if (auto overload = findSelectedOverloadFor(getCalleeLocator(argLoc))) {
+          auto *overloadTy =
+              simplifyType(overload->boundType)->castTo<FunctionType>();
+          auto *argList = getArgumentList(argLoc);
+          ASSERT(argList);
+          conversionsOrFixes.push_back(AllowArgumentMismatch::create(
+              *this, getType(argList->getExpr(argIdx)),
+              overloadTy->getParams()[paramIdx].getPlainType(), argLoc));
+          return true;
+        }
+      }
     }
 
     // When the solver sets `TMF_MatchingGenericArguments` it means
@@ -6915,12 +6942,19 @@ bool ConstraintSystem::repairFailures(
     path.pop_back();
 
     ConstraintFix *fix = nullptr;
-    if (!path.empty() && path.back().is<LocatorPathElt::AnyRequirement>()) {
+    auto *fixLoc = getConstraintLocator(anchor, path);
+
+    if (fixLoc->isLastElement<LocatorPathElt::AnyRequirement>()) {
       fix = fixRequirementFailure(*this, fromType, toType, anchor, path);
+    } else if (fixLoc->isLastElement<LocatorPathElt::TupleElement>()) {
+      return repairFailures(lhs, rhs, matchKind, flags, conversionsOrFixes,
+                            fixLoc);
+    } else if (!lhs->mayHaveSuperclass() && rhs->isAnyObject()) {
+      fix = AllowNonClassTypeToConvertToAnyObject::create(*this, fromType,
+                                                          fixLoc);
     } else {
       fix = GenericArgumentsMismatch::create(
-          *this, fromType, toType, {genericArgElt.getIndex()},
-          getConstraintLocator(anchor, path));
+          *this, fromType, toType, {genericArgElt.getIndex()}, fixLoc);
     }
 
     if (!fix)
@@ -11410,6 +11444,14 @@ ConstraintSystem::SolutionKind ConstraintSystem::simplifyMemberConstraint(
             // `key path` constraint can't be retired until all components
             // are simplified.
             addTypeVariableConstraintsToWorkList(memberTypeVar);
+          } else if (locator->getAnchor().is<Expr *>() &&
+                     !getSemanticsProvidingParentExpr(
+                         getAsExpr(locator->getAnchor()))) {
+            // If there are no contextual expressions that could provide
+            // a type for the member type variable, let's default it to
+            // a placeholder eagerly so it could be propagated to the
+            // pattern if necessary.
+            recordTypeVariablesAsHoles(memberTypeVar);
           } else if (locator->isLastElement<LocatorPathElt::PatternMatch>()) {
             // Let's handle member patterns specifically because they use
             // equality instead of argument application constraint, so allowing
@@ -15649,14 +15691,31 @@ ConstraintSystem::SolutionKind ConstraintSystem::simplifyFixConstraint(
   case FixKind::AllowFunctionSpecialization:
   case FixKind::IgnoreGenericSpecializationArityMismatch:
   case FixKind::IgnoreKeyPathSubscriptIndexMismatch:
-  case FixKind::AllowMemberRefOnExistential: {
+  case FixKind::AllowMemberRefOnExistential:
+  case FixKind::AllowNonClassTypeToConvertToAnyObject: {
     return recordFix(fix) ? SolutionKind::Error : SolutionKind::Solved;
   }
 
   case FixKind::GenericArgumentsMismatch: {
     unsigned impact = 1;
     if (type1->isMarkerExistential() || type2->isMarkerExistential())
       ++impact;
+
+    // If generic arguments mismatch ends up being recorded on the result
+    // of the chain or a try expression it means that there is a contextual 
+    // conversion mismatch.
+    //
+    // For optional conversions the solver currently generates a disjunction
+    // with two choices - bind and optional-to-optional conversion which is
+    // anchored on the contextual expression. If we can get a fix recorded
+    // there that would result in a better diagnostic. It's only possible
+    // for optional-to-optional choice because it doesn't bind the
+    // variable immediately, so we need to downgrade direct fixes to prevent
+    // `bind` choice from considered better.
+    if (fix->directlyAt<OptionalEvaluationExpr>() ||
+        fix->directlyAt<AnyTryExpr>())
+      impact += 2;
+
     return recordFix(fix, impact) ? SolutionKind::Error : SolutionKind::Solved;
   }
 
@@ -15884,7 +15943,6 @@ ConstraintSystem::SolutionKind ConstraintSystem::simplifyFixConstraint(
   case FixKind::DefaultGenericArgument:
   case FixKind::AllowMutatingMemberOnRValueBase:
   case FixKind::AllowTupleSplatForSingleParameter:
-  case FixKind::AllowNonClassTypeToConvertToAnyObject:
   case FixKind::SpecifyClosureParameterType:
   case FixKind::SpecifyClosureReturnType:
   case FixKind::AddQualifierToAccessTopLevelName:

test/ClangImporter/MixedSource/mixed-target-using-header.swift

@@ -66,11 +66,13 @@ func testProtocolNamingConflict() {
   let a: ConflictingName1?
   var b: ConflictingName1Protocol?
   b = a // expected-error {{cannot assign value of type 'ConflictingName1?' to type '(any ConflictingName1Protocol)?'}}
+  // expected-note@-1 {{arguments to generic parameter 'Wrapped' ('ConflictingName1' and 'any ConflictingName1Protocol') are expected to be equal}}
   _ = b
 
   let c: ConflictingName2?
   var d: ConflictingName2Protocol?
   d = c // expected-error {{cannot assign value of type 'ConflictingName2?' to type '(any ConflictingName2Protocol)?'}}
+  // expected-note@-1 {{arguments to generic parameter 'Wrapped' ('ConflictingName2' and 'any ConflictingName2Protocol') are expected to be equal}}
   _ = d
 }
 

test/ClangImporter/cf.swift

@@ -118,6 +118,7 @@ func testOutParametersGood() {
 func testOutParametersBad() {
   let fridge: CCRefrigerator?
   CCRefrigeratorCreateIndirect(fridge) // expected-error {{cannot convert value of type 'CCRefrigerator?' to expected argument type 'UnsafeMutablePointer<CCRefrigerator?>?'}}
+  // expected-note@-1 {{arguments to generic parameter 'Wrapped' ('CCRefrigerator' and 'UnsafeMutablePointer<CCRefrigerator?>') are expected to be equal}}
 
   let power: CCPowerSupply?
   CCRefrigeratorGetPowerSupplyIndirect(0, power)
@@ -128,21 +129,26 @@ func testOutParametersBad() {
   CCRefrigeratorGetItemUnaudited(0, 0, item)
   // expected-error@-1:34 {{cannot convert value of type 'Int' to expected argument type 'CCRefrigerator'}}
   // expected-error@-2:40 {{cannot convert value of type 'CCItem?' to expected argument type 'UnsafeMutablePointer<Unmanaged<CCItem>?>?'}}
+  // expected-note@-3 {{arguments to generic parameter 'Wrapped' ('CCItem' and 'UnsafeMutablePointer<Unmanaged<CCItem>?>') are expected to be equal}}
 }
 
 func nameCollisions() {
   var objc: MyProblematicObject?
   var cf: MyProblematicObjectRef?
   cf = objc // expected-error {{cannot assign value of type 'MyProblematicObject?' to type 'MyProblematicObjectRef?'}}
+  // expected-note@-1 {{arguments to generic parameter 'Wrapped' ('MyProblematicObject' and 'MyProblematicObjectRef') are expected to be equal}}
   objc = cf // expected-error {{cannot assign value of type 'MyProblematicObjectRef?' to type 'MyProblematicObject?'}}
+  // expected-note@-1 {{arguments to generic parameter 'Wrapped' ('MyProblematicObjectRef' and 'MyProblematicObject') are expected to be equal}}
 
   var cfAlias: MyProblematicAliasRef?
   cfAlias = cf // okay
   cf = cfAlias // okay
 
   var otherAlias: MyProblematicAlias?
   otherAlias = cfAlias // expected-error {{cannot assign value of type 'MyProblematicAliasRef?' (aka 'Optional<MyProblematicObjectRef>') to type 'MyProblematicAlias?' (aka 'Optional<Float>')}}
+  // expected-note@-1 {{arguments to generic parameter 'Wrapped' ('MyProblematicAliasRef' (aka 'MyProblematicObjectRef') and 'MyProblematicAlias' (aka 'Float')) are expected to be equal}}
   cfAlias = otherAlias // expected-error {{cannot assign value of type 'MyProblematicAlias?' (aka 'Optional<Float>') to type 'MyProblematicAliasRef?' (aka 'Optional<MyProblematicObjectRef>')}}
+  // expected-note@-1 {{arguments to generic parameter 'Wrapped' ('MyProblematicAlias' (aka 'Float') and 'MyProblematicAliasRef' (aka 'MyProblematicObjectRef')) are expected to be equal}}
 
   func isOptionalFloat(_: inout Optional<Float>) {}
   isOptionalFloat(&otherAlias) // okay

test/ClangImporter/ctypes_parse.swift

@@ -214,6 +214,7 @@ func testFunctionPointers() {
 
   useFunctionPointer2(anotherFP)
   sizedFP = fp // expected-error {{cannot assign value of type 'fptr?' (aka 'Optional<@convention(c) (Int32) -> Int32>') to type '(@convention(c) (CInt, CInt, UnsafeMutableRawPointer?) -> Void)?'}}
+  // expected-note@-1 {{arguments to generic parameter 'Wrapped' ('fptr' (aka '@convention(c) (Int32) -> Int32') and '@convention(c) (CInt, CInt, UnsafeMutableRawPointer?) -> Void'}}
 }
 
 func testStructDefaultInit() {