Merge pull request #36208 from LucianoPAlmeida/SR-14280-ambiguity-repr

[SR-14280][CSSimplify] Increase the score when matching functions with different representations for contextual type

Author: LucianoPAlmeida

lib/Sema/CSSimplify.cpp

@@ -2013,6 +2013,16 @@ ConstraintSystem::matchFunctionTypes(FunctionType *func1, FunctionType *func2,
       return getTypeMatchFailure(locator);
   }
 
+  // To contextual type increase the score to avoid ambiguity when solver can
+  // find more than one viable binding different only in representation e.g.
+  //   let _: (@convention(block) () -> Void)? = Bool.random() ? nil : {}
+  // so same representation should be always favored.
+  auto loc = getConstraintLocator(locator);
+  if (loc->findLast<LocatorPathElt::ContextualType>() &&
+      func1->getRepresentation() != func2->getRepresentation()) {
+    increaseScore(SK_FunctionConversion);
+  }
+
   if (!matchFunctionRepresentations(func1->getExtInfo(), func2->getExtInfo(),
                                     kind, Options)) {
     return getTypeMatchFailure(locator);

test/Constraints/closures.swift

@@ -1068,3 +1068,12 @@ func rdar_74435602(error: Error?) {
     }
   })
 }
+
+// SR-14280
+let _: (@convention(block) () -> Void)? = Bool.random() ? nil : {} // OK
+let _: (@convention(thin) () -> Void)? = Bool.random() ? nil : {} // OK
+let _: (@convention(c) () -> Void)? = Bool.random() ? nil : {} // OK on type checking, diagnostics are deffered to SIL
+
+let _: (@convention(block) () -> Void)? = Bool.random() ? {} : {} // OK
+let _: (@convention(thin) () -> Void)? = Bool.random() ? {} : {} // OK
+let _: (@convention(c) () -> Void)? = Bool.random() ? {} : {} // OK on type checking, diagnostics are deffered to SIL