stdlib: map wchar_t to UInt16 on Windows

This is an ABI breaking change for Windows.  `WCHAR` on Windows is
mapped to `short` (`-fshort-wchar` makes it `unsigned short`).  When C++
interop is enabled, `WCHAR` will be mapped to `wchar_t` which is then
mapped to `short` (or `unsigned short` if `-fshort-wchar` is specified).
Correct the mapping type to get the desired behaviour.

stdlib/public/core/CTypes.swift

@@ -116,7 +116,11 @@ public typealias CLongDouble = Float80
 // FIXME: Is it actually UTF-32 on Darwin?
 //
 /// The C++ 'wchar_t' type.
+#if os(Windows)
+public typealias CWideChar = UInt16
+#else
 public typealias CWideChar = Unicode.Scalar
+#endif
 
 // FIXME: Swift should probably have a UTF-16 type other than UInt16.
 //

test/ClangImporter/Inputs/unicode/module.modulemap

@@ -0,0 +1,4 @@
+module unicode {
+  header "unicode.h"
+  export *
+}

test/ClangImporter/Inputs/unicode/unicode.h

@@ -0,0 +1,6 @@
+
+#if !defined(__cplusplus)
+typedef short wchar_t;
+#endif
+typedef wchar_t WCHAR;
+#define UNICODE_NULL ((WCHAR)0)

test/ClangImporter/unicode.swift

@@ -0,0 +1,10 @@
+// RUN: %swift-ide-test -target x86_64-unknown-windows-msvc -print-module -module-to-print unicode -print-interface -source-filename %s -I %S/Inputs/unicode | %FileCheck %s -check-prefix CHECK-C
+// RUN: %swift-ide-test -target x86_64-unknown-windows-msvc -enable-experimental-cxx-interop -print-module -module-to-print unicode -print-interface -source-filename %s -I %S/Inputs/unicode | %FileCheck %s -check-prefix CHECK-CXX
+
+// REQUIRES: OS=windows-msvc
+
+import unicode
+
+// CHECK-C: typealias WCHAR = wchar_t
+// CHECK-CXX: typealias WCHAR = CWideChar
+// CHECK: var UNICODE_NULL: WCHAR { get }

test/Interop/SwiftToC/functions/swift-primitive-functions-c-bridging.swift

@@ -1,6 +1,6 @@
 // RUN: %empty-directory(%t)
 // RUN: %target-swift-frontend %s -typecheck -module-name Functions -clang-header-expose-decls=all-public -emit-clang-header-path %t/functions.h
-// RUN: %FileCheck %s < %t/functions.h
+// RUN: %FileCheck %s -check-prefix CHECK -check-prefix CHECK-%target-abi < %t/functions.h
 
 // RUN: %check-interop-c-header-in-clang(%t/functions.h)
 
@@ -19,7 +19,8 @@
 // CHECK-NEXT: SWIFT_EXTERN unsigned long long $s9Functions024passThroughCUnsignedLongE0ys6UInt64VADF(unsigned long long x) SWIFT_NOEXCEPT SWIFT_CALL;
 // CHECK-NEXT: SWIFT_EXTERN unsigned short $s9Functions25passThroughCUnsignedShortys6UInt16VADF(unsigned short x) SWIFT_NOEXCEPT SWIFT_CALL;
 // CHECK-NEXT: SWIFT_EXTERN unsigned char $s9Functions30passThroughCUnsignedSignedCharys5UInt8VADF(unsigned char x) SWIFT_NOEXCEPT SWIFT_CALL;
-// CHECK-NEXT: SWIFT_EXTERN wchar_t $s9Functions20passThroughCWideCharys7UnicodeO6ScalarVAFF(wchar_t x) SWIFT_NOEXCEPT SWIFT_CALL;
+// CHECK-SYSV-NEXT: SWIFT_EXTERN wchar_t $s9Functions20passThroughCWideCharys7UnicodeO6ScalarVAFF(wchar_t x) SWIFT_NOEXCEPT SWIFT_CALL;
+// CHECK-WIN-NEXT: SWIFT_EXTERN wchar_t $s9Functions20passThroughCWideCharys6UInt16VADF(wchar_t x) SWIFT_NOEXCEPT SWIFT_CALL;
 // CHECK-NEXT: SWIFT_EXTERN double $s9Functions17passThroughDoubleyS2dF(double x) SWIFT_NOEXCEPT SWIFT_CALL;
 // CHECK-NEXT: SWIFT_EXTERN float $s9Functions16passThroughFloatyS2fF(float x) SWIFT_NOEXCEPT SWIFT_CALL;
 // CHECK-NEXT: SWIFT_EXTERN float $s9Functions18passThroughFloat32yS2fF(float x) SWIFT_NOEXCEPT SWIFT_CALL;

test/Interop/SwiftToC/functions/swift-primitive-functions-execution.c

@@ -22,7 +22,11 @@ int main() {
   // passThroughCChar
   VERIFY_PASSTHROUGH_VALUE($s9Functions16passThroughCCharys4Int8VADF, 'a');
   // passThroughCWideChar
+#if defined(_WIN32)
+  VERIFY_PASSTHROUGH_VALUE($s9Functions20passThroughCWideCharys6UInt16VADF, 'a');
+#else
   VERIFY_PASSTHROUGH_VALUE($s9Functions20passThroughCWideCharys7UnicodeO6ScalarVAFF, 'a');
+#endif
   // passThroughCChar16
   VERIFY_PASSTHROUGH_VALUE($s9Functions18passThroughCChar16ys6UInt16VADF, 0xFE1);
   // passThroughCChar32

test/Interop/SwiftToCxx/functions/swift-primitive-functions-cxx-bridging.swift

@@ -1,6 +1,6 @@
 // RUN: %empty-directory(%t)
 // RUN: %target-swift-frontend %s -typecheck -module-name Functions -clang-header-expose-decls=all-public -emit-clang-header-path %t/functions.h
-// RUN: %FileCheck %s < %t/functions.h
+// RUN: %FileCheck %s -check-prefix CHECK -check-prefix CHECK-%target-abi < %t/functions.h
 
 // RUN: %check-interop-cxx-header-in-clang(%t/functions.h)
 
@@ -67,7 +67,8 @@
 // CHECK-NEXT: }
 
 // CHECK:      SWIFT_INLINE_THUNK wchar_t passThroughCWideChar(wchar_t x) noexcept SWIFT_SYMBOL({{.*}}) SWIFT_WARN_UNUSED_RESULT {
-// CHECK-NEXT:   return _impl::$s9Functions20passThroughCWideCharys7UnicodeO6ScalarVAFF(x);
+// CHECK-SYSV:   return _impl::$s9Functions20passThroughCWideCharys7UnicodeO6ScalarVAFF(x);
+// CHECK-WIN:   return _impl::$s9Functions20passThroughCWideCharys6UInt16VADF(x);
 // CHECK-NEXT: }
 
 // CHECK:      SWIFT_INLINE_THUNK double passThroughDouble(double x) noexcept SWIFT_SYMBOL({{.*}}) SWIFT_WARN_UNUSED_RESULT {

test/stdlib/PrintInteger.swift

@@ -34,7 +34,11 @@ PrintTests.test("CustomStringConvertible") {
   hasDescription(CInt(42))
   hasDescription(CLong(42))
   hasDescription(CLongLong(42))
+#if os(Windows)
+  hasDescription(CWideChar(exactly: 42)!)
+#else
   hasDescription(CWideChar(42)!)
+#endif
   hasDescription(CChar16(42))
   hasDescription(CChar32(42)!)
 }
@@ -51,7 +55,11 @@ PrintTests.test("Printable") {
   expectPrinted("42", CInt(42))
   expectPrinted("42", CLong(42))
   expectPrinted("42", CLongLong(42))
+#if os(Windows)
+  expectPrinted("42", CWideChar(exactly: 42)!)
+#else
   expectPrinted("*", CWideChar(42)!)
+#endif
   expectPrinted("42", CChar16(42))
   expectPrinted("*", CChar32(42)!)
 
@@ -142,7 +150,11 @@ PrintTests.test("Printable") {
   expectPrinted("42", CLong(42))
   expectPrinted("42", CLongLong(42))
 
+#if os(Windows)
+  expectPrinted("42", CWideChar(exactly: 42)!)
+#else
   expectPrinted("*", CWideChar(42)!)
+#endif
   expectPrinted("42", CChar16(42))
   expectPrinted("*", CChar32(42)!)
 }