Revert "[CSSolver] Use correct locator when matching function result types related to closures"

This reverts commit 503d2d8.

Author: xedin

lib/Sema/CSRanking.cpp

@@ -1027,32 +1027,14 @@ SolutionCompareResult ConstraintSystem::compareSolutions(
   // Compare the type variable bindings.
   auto &tc = cs.getTypeChecker();
   for (auto &binding : diff.typeBindings) {
-    auto type1 = binding.bindings[idx1];
-    auto type2 = binding.bindings[idx2];
-
-    auto &impl = binding.typeVar->getImpl();
-
-    if (auto *locator = impl.getLocator()) {
-      auto path = locator->getPath();
-      if (!path.empty() &&
-          path.back().getKind() == ConstraintLocator::ClosureResult) {
-        // Since we support `() -> T` to `() -> Void` and
-        // `() -> Never` to `() -> T` conversions, it's always
-        // preferable to pick `T` rather than `Never` with
-        // all else being equal.
-        if (type2->isUninhabited())
-          ++score1;
-
-        if (type1->isUninhabited())
-          ++score2;
-      }
-    }
-
     // If the type variable isn't one for which we should be looking at the
     // bindings, don't.
-    if (!impl.prefersSubtypeBinding())
+    if (!binding.typeVar->getImpl().prefersSubtypeBinding())
       continue;
 
+    auto type1 = binding.bindings[idx1];
+    auto type2 = binding.bindings[idx2];
+
     // If the types are equivalent, there's nothing more to do.
     if (type1->isEqual(type2))
       continue;

lib/Sema/CSSimplify.cpp

@@ -1235,8 +1235,10 @@ ConstraintSystem::matchFunctionTypes(FunctionType *func1, FunctionType *func2,
   }
 
   // Result type can be covariant (or equal).
-  return matchTypes(func1->getResult(), func2->getResult(), subKind, subflags,
-                    locator.withPathElement(ConstraintLocator::FunctionResult));
+  return matchTypes(func1->getResult(), func2->getResult(), subKind,
+                     subflags,
+                     locator.withPathElement(
+                       ConstraintLocator::FunctionResult));
 }
 
 ConstraintSystem::SolutionKind
@@ -1562,8 +1564,6 @@ ConstraintSystem::SolutionKind
 ConstraintSystem::matchTypes(Type type1, Type type2, ConstraintKind kind,
                              TypeMatchOptions flags,
                              ConstraintLocatorBuilder locator) {
-  auto origType1 = type1;
-
   bool isArgumentTupleConversion
           = kind == ConstraintKind::ArgumentTupleConversion ||
             kind == ConstraintKind::OperatorArgumentTupleConversion;
@@ -2324,32 +2324,7 @@ ConstraintSystem::matchTypes(Type type1, Type type2, ConstraintKind kind,
   // Allow '() -> T' to '() -> ()' and '() -> Never' to '() -> T' for closure
   // literals.
   if (auto elt = locator.last()) {
-    auto isClosureResult = [&]() {
-      if (elt->getKind() == ConstraintLocator::ClosureResult)
-        return true;
-
-      // If constraint is matching function results where
-      // left-hand side is a 'closure result' we need to allow
-      // certain implicit conversions.
-      if (elt->getKind() != ConstraintLocator::FunctionResult)
-        return false;
-
-      if (auto *typeVar = origType1->getAs<TypeVariableType>()) {
-        auto *locator = typeVar->getImpl().getLocator();
-        if (!locator)
-          return false;
-
-        auto path = locator->getPath();
-        if (path.empty())
-          return false;
-
-        return path.back().getKind() == ConstraintLocator::ClosureResult;
-      }
-
-      return false;
-    };
-
-    if (isClosureResult()) {
+    if (elt->getKind() == ConstraintLocator::ClosureResult) {
       if (concrete && kind >= ConstraintKind::Subtype &&
           (type1->isUninhabited() || type2->isVoid())) {
         increaseScore(SK_FunctionConversion);

test/Constraints/closures.swift

@@ -630,6 +630,7 @@ func rdar33429010_2() {
   let iter = I_33429010()
   var acc: Int = 0 // expected-warning {{}}
   let _: Int = AnySequence { iter }.rdar33429010(into: acc, { $0 + $1 })
+  // expected-warning@-1 {{result of operator '+' is unused}}
   let _: Int = AnySequence { iter }.rdar33429010(into: acc, { $0.rdar33429010_incr($1) })
 }
 
@@ -651,16 +652,3 @@ func rdar36054961() {
      str.replaceSubrange(range, with: str[range].reversed())
   }])
 }
-
-func rdar37790062() {
-  struct S<T> {
-    init(_ a: () -> T, _ b: () -> T) {}
-  }
-
-  func foo() -> Int { return 42 }
-  func bar() -> Void {}
-  func baz() -> (String, Int) { return ("question", 42) }
-
-  _ = S({ foo() }, { bar() }) // Ok, should infer T to be 'Void'
-  _ = S({ baz() }, { bar() }) // Ok, should infer T to be 'Void'
-}

test/Constraints/rdar37790062.swift

@@ -259,6 +259,7 @@ func rdar19179412() -> (Int) -> Int {
 func takesVoidFunc(_ f: () -> ()) {}
 var i: Int = 1
 
+// expected-warning @+1 {{expression of type 'Int' is unused}}
 takesVoidFunc({i})
 // expected-warning @+1 {{expression of type 'Int' is unused}}
 var f1: () -> () = {i}