[ConstraintSystem] Fix single tuple vs. N arguments in function conversions

Author: xedin

lib/Sema/CSSimplify.cpp

@@ -1435,7 +1435,7 @@ static bool fixMissingArguments(ConstraintSystem &cs, Expr *anchor,
   // (which might be anonymous), it's most likely used as a
   // tuple e.g. `$0.0`.
   Optional<TypeBase *> argumentTuple;
-  if (isa<ClosureExpr>(anchor) && isSingleTupleParam(ctx, args)) {
+  if (isSingleTupleParam(ctx, args)) {
     auto argType = args.back().getPlainType();
     // Let's unpack argument tuple into N arguments, this corresponds
     // to something like `foo { (bar: (Int, Int)) in }` where `foo`
@@ -1456,24 +1456,26 @@ static bool fixMissingArguments(ConstraintSystem &cs, Expr *anchor,
       };
 
       // Something like `foo { x in }` or `foo { $0 }`
-      anchor->forEachChildExpr([&](Expr *expr) -> Expr * {
-        if (auto *UDE = dyn_cast<UnresolvedDotExpr>(expr)) {
-          if (!isParam(UDE->getBase()))
-            return expr;
-
-          auto name = UDE->getName().getBaseIdentifier();
-          unsigned index = 0;
-          if (!name.str().getAsInteger(10, index) ||
-              llvm::any_of(params, [&](const AnyFunctionType::Param &param) {
-                return param.getLabel() == name;
-              })) {
-            argumentTuple.emplace(typeVar);
-            args.pop_back();
-            return nullptr;
+      if (isa<ClosureExpr>(anchor)) {
+        anchor->forEachChildExpr([&](Expr *expr) -> Expr * {
+          if (auto *UDE = dyn_cast<UnresolvedDotExpr>(expr)) {
+            if (!isParam(UDE->getBase()))
+              return expr;
+
+            auto name = UDE->getName().getBaseIdentifier();
+            unsigned index = 0;
+            if (!name.str().getAsInteger(10, index) ||
+                llvm::any_of(params, [&](const AnyFunctionType::Param &param) {
+                  return param.getLabel() == name;
+                })) {
+              argumentTuple.emplace(typeVar);
+              args.pop_back();
+              return nullptr;
+            }
           }
-        }
-        return expr;
-      });
+          return expr;
+        });
+      }
     }
   }
 

test/Constraints/tuple_arguments.swift

@@ -1657,14 +1657,14 @@ public extension Optional {
 // https://bugs.swift.org/browse/SR-6837
 
 // FIXME: Can't overlaod local functions so these must be top-level
-func takePairOverload(_ pair: (Int, Int?)) {} // expected-note {{found this candidate}}
-func takePairOverload(_: () -> ()) {} // expected-note {{found this candidate}}
+func takePairOverload(_ pair: (Int, Int?)) {}
+func takePairOverload(_: () -> ()) {}
 
 do {
   func takeFn(fn: (_ i: Int, _ j: Int?) -> ()) {}
   func takePair(_ pair: (Int, Int?)) {}
   takeFn(fn: takePair) // expected-error {{cannot convert value of type '((Int, Int?)) -> ()' to expected argument type '(Int, Int?) -> ()'}}
-  takeFn(fn: takePairOverload) // expected-error {{ambiguous reference to member 'takePairOverload'}}
+  takeFn(fn: takePairOverload) // expected-error {{cannot convert value of type '((Int, Int?)) -> ()' to expected argument type '(Int, Int?) -> ()'}}
   takeFn(fn: { (pair: (Int, Int?)) in } ) // Disallow for -swift-version 4 and later
   // expected-error@-1 {{contextual closure type '(Int, Int?) -> ()' expects 2 arguments, but 1 was used in closure body}}
   takeFn { (pair: (Int, Int?)) in } // Disallow for -swift-version 4 and later