[Constraint system] Move closure type checking to a separate file.

Author: DougGregor

lib/Sema/CMakeLists.txt

@@ -2,6 +2,7 @@ add_swift_host_library(swiftSema STATIC
   BuilderTransform.cpp
   CSApply.cpp
   CSBindings.cpp
+  CSClosure.cpp
   CSGen.cpp
   CSRanking.cpp
   CSSimplify.cpp

lib/Sema/CSClosure.cpp

@@ -0,0 +1,37 @@
+//===--- CSClosure.cpp - Closures -----------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements constraint generation and solution application for
+// closures. It provides part of the implementation of the ConstraintSystem
+// class.
+//
+//===----------------------------------------------------------------------===//
+
+#include "ConstraintSystem.h"
+using namespace swift;
+using namespace swift::constraints;
+
+bool ConstraintSystem::generateConstraints(
+    ClosureExpr *closure, Type resultType) {
+  assert(closure->hasSingleExpressionBody());
+  auto closureBody = generateConstraints(
+      closure->getSingleExpressionBody(), closure, /*isInputExpression=*/false);
+  if (!closureBody)
+    return true;
+
+  bool hasReturn = hasExplicitResult(closure);
+  addConstraint(
+      ConstraintKind::Conversion, getType(closureBody),
+      resultType,
+      getConstraintLocator(closure, LocatorPathElt::ClosureBody(hasReturn)));
+  return false;
+}

lib/Sema/CSGen.cpp

@@ -4418,24 +4418,10 @@ bool ConstraintSystem::generateConstraints(
   llvm_unreachable("BOOM");
 }
 
-bool ConstraintSystem::generateConstraints(
-    ClosureExpr *closure, Type resultType) {
-  assert(closure->hasSingleExpressionBody());
-  auto closureBody = generateConstraintsFor(
-      *this, closure->getSingleExpressionBody(), closure);
-  if (!closureBody)
-    return true;
-
-  bool hasReturn = hasExplicitResult(closure);
-  addConstraint(
-      ConstraintKind::Conversion, getType(closureBody),
-      resultType,
-      getConstraintLocator(closure, LocatorPathElt::ClosureBody(hasReturn)));
-  return false;
-}
-
-Expr *ConstraintSystem::generateConstraints(Expr *expr, DeclContext *dc) {
-  InputExprs.insert(expr);
+Expr *ConstraintSystem::generateConstraints(
+    Expr *expr, DeclContext *dc, bool isInputExpression) {
+  if (isInputExpression)
+    InputExprs.insert(expr);
   return generateConstraintsFor(*this, expr, dc);
 }
 

lib/Sema/ConstraintSystem.h

@@ -3587,7 +3587,8 @@ class ConstraintSystem {
   /// Generate constraints for the given (unchecked) expression.
   ///
   /// \returns a possibly-sanitized expression, or null if an error occurred.
-  Expr *generateConstraints(Expr *E, DeclContext *dc);
+  Expr *generateConstraints(Expr *E, DeclContext *dc,
+                            bool isInputExpression = true);
 
   /// Generate constraints for binding the given pattern to the
   /// value of the given expression.