Merge pull request swiftlang#35247 from LucianoPAlmeida/SR-14003-Self

[Sema][Diagnostics] Avoid recording treat as rvalue fix if destination expr type is a type var that can bind to lvalue

Author: LucianoPAlmeida

lib/Sema/CSSimplify.cpp

@@ -3748,7 +3748,12 @@ bool ConstraintSystem::repairFailures(
       // a property with a function type or a method reference,
       // e.g. `foo.bar = 42` neither can be used if the destination
       // is not l-value.
-      if (!getType(destExpr)->is<LValueType>() && rhs->is<FunctionType>()) {
+      auto destType = getType(destExpr);
+      auto destTypeVar = destType->getAs<TypeVariableType>();
+      bool destIsOrCanBindToLValue =
+          destType->is<LValueType>() ||
+          (destTypeVar && destTypeVar->getImpl().canBindToLValue());
+      if (!destIsOrCanBindToLValue && rhs->is<FunctionType>()) {
         conversionsOrFixes.push_back(
             TreatRValueAsLValue::create(*this, getConstraintLocator(locator)));
         return true;
@@ -3772,9 +3777,9 @@ bool ConstraintSystem::repairFailures(
                                TMF_ApplyingFix, locator);
 
       auto *loc = getConstraintLocator(locator);
-      if (getType(destExpr)->is<LValueType>() || result.isFailure()) {
-        // Let this asignment failure be diagnosed by the AllowTupleTypeMismatch
-        // fix already recorded.
+      if (destIsOrCanBindToLValue || result.isFailure()) {
+        // Let this assignment failure be diagnosed by the
+        // AllowTupleTypeMismatch fix already recorded.
         if (hasFixFor(loc, FixKind::AllowTupleTypeMismatch))
           return true;
 

test/Constraints/assignment.swift

@@ -77,3 +77,12 @@ func f23798944() {
 
 func returnsVoid() {}
 _ = returnsVoid() // expected-warning {{using '_' to ignore the result of a Void-returning function is redundant}}{{1-5=}}
+
+// SR-14003
+class SR14003 {
+  var callback: ((SR14003) -> Void)!
+  
+  func setCallback(_ callback: @escaping (Self) -> Void) {
+    self.callback = callback // expected-error {{cannot assign value of type '(Self) -> Void' to type '((SR14003) -> Void)?'}}
+  }
+}