[AST] Fix canonicalization of the function input types

Currently canonicalization of the input type was happening standalone
which means that outer parens are regarded as suger and removed,
this is incorrect after SE-0110 and such parens can't be stripped.

Author: xedin

lib/AST/Type.cpp

@@ -1022,6 +1022,27 @@ void ProtocolType::canonicalizeProtocols(
   llvm::array_pod_sort(protocols.begin(), protocols.end(), compareProtocols);
 }
 
+static Type
+getCanonicalInputType(AnyFunctionType *funcType,
+                      llvm::function_ref<CanType(Type)> getCanonicalType) {
+  auto origInputType = funcType->getInput();
+  bool isParen = isa<ParenType>(origInputType.getPointer());
+  Type inputType = getCanonicalType(origInputType);
+
+  if (!isParen && AnyFunctionType::isCanonicalFunctionInputType(inputType))
+    return inputType;
+
+  auto flags = ParameterTypeFlags().withInOut(inputType->is<InOutType>());
+  if (auto *parenTy = dyn_cast<ParenType>(origInputType.getPointer()))
+    flags = flags.withShared(parenTy->getParameterFlags().isShared());
+
+  inputType = ParenType::get(inputType->getASTContext(),
+                             inputType->getInOutObjectType(), flags);
+  assert(AnyFunctionType::isCanonicalFunctionInputType(inputType));
+
+  return inputType;
+}
+
 /// getCanonicalType - Return the canonical version of this type, which has
 /// sugar from all levels stripped off.
 CanType TypeBase::getCanonicalType() {
@@ -1124,15 +1145,10 @@ CanType TypeBase::getCanonicalType() {
     // Transform the input and result types.
     auto &ctx = function->getInput()->getASTContext();
     auto &mod = *ctx.TheBuiltinModule;
-    Type inputTy = function->getInput()->getCanonicalType(sig, mod);
-    if (!AnyFunctionType::isCanonicalFunctionInputType(inputTy)) {
-      auto flags = ParameterTypeFlags().withInOut(inputTy->is<InOutType>());
-      if (auto parenTy = dyn_cast<ParenType>(function->getInput().getPointer()))
-        flags = flags.withShared(parenTy->getParameterFlags().isShared());
-      inputTy = ParenType::get(ctx, inputTy->getInOutObjectType(), flags);
-    }
+    auto inputTy = getCanonicalInputType(function, [&](Type type) -> CanType {
+      return type->getCanonicalType(sig, mod);
+    });
     auto resultTy = function->getResult()->getCanonicalType(sig, mod);
-
     Result = GenericFunctionType::get(sig, inputTy, resultTy,
                                       function->getExtInfo());
     assert(Result->isCanonical());
@@ -1146,14 +1162,8 @@ CanType TypeBase::getCanonicalType() {
 
   case TypeKind::Function: {
     FunctionType *FT = cast<FunctionType>(this);
-    Type In = FT->getInput()->getCanonicalType();
-    if (!AnyFunctionType::isCanonicalFunctionInputType(In)) {
-      auto flags = ParameterTypeFlags().withInOut(In->is<InOutType>());
-      if (auto parenTy = dyn_cast<ParenType>(FT->getInput().getPointer()))
-        flags = flags.withShared(parenTy->getParameterFlags().isShared());
-      In = ParenType::get(In->getASTContext(), In->getInOutObjectType(), flags);
-      assert(AnyFunctionType::isCanonicalFunctionInputType(In));
-    }
+    auto In = getCanonicalInputType(
+        FT, [](Type type) -> CanType { return type->getCanonicalType(); });
     Type Out = FT->getResult()->getCanonicalType();
     Result = FunctionType::get(In, Out, FT->getExtInfo());
     break;

test/Constraints/diagnostics.swift

@@ -97,7 +97,7 @@ func f8<T:P2>(_ n: T, _ f: @escaping (T) -> T) {}
 f8(3, f4) // expected-error {{in argument type '(Int) -> Int', 'Int' does not conform to expected type 'P2'}}
 typealias Tup = (Int, Double)
 func f9(_ x: Tup) -> Tup { return x }
-f8((1,2.0), f9) // expected-error {{in argument type '(Tup) -> Tup' (aka '(Int, Double) -> (Int, Double)'), 'Tup' (aka '(Int, Double)') does not conform to expected type 'P2'}}
+f8((1,2.0), f9) // expected-error {{in argument type '(Tup) -> Tup' (aka '((Int, Double)) -> (Int, Double)'), 'Tup' (aka '(Int, Double)') does not conform to expected type 'P2'}}
 
 // <rdar://problem/19658691> QoI: Incorrect diagnostic for calling nonexistent members on literals
 1.doesntExist(0)  // expected-error {{value of type 'Int' has no member 'doesntExist'}}