Sema: Add @cdecl @implementation type-checking test variant

Based off the test for `@_cdecl @implementation`. Split between need of
the ObjC interop.

Author: xymus

test/decl/ext/Inputs/objc_implementation.h

@@ -231,6 +231,8 @@
 void CImplFunc1(int param);
 void CImplFunc2(int param);
 
+void CImplFuncRenamed_C(int param) __attribute__((swift_name("CImplFuncRenamed_Swift(arg:)")));
+
 void CImplFuncMismatch1(int param);
 void CImplFuncMismatch2(int param);
 

test/decl/ext/cdecl_official_implementation.swift

@@ -0,0 +1,82 @@
+// RUN: %target-typecheck-verify-swift -target %target-stable-abi-triple \
+// RUN:   -import-bridging-header %S/Inputs/objc_implementation.h \
+// RUN:   -disable-objc-interop \
+// RUN:   -enable-experimental-feature CImplementation \
+// RUN:   -enable-experimental-feature CDecl
+
+// REQUIRES: swift_feature_CImplementation
+// REQUIRES: swift_feature_CDecl
+
+@implementation @cdecl
+func CImplFunc1(_: Int32) {
+  // OK
+}
+
+@implementation @cdecl(CImplFuncRenamed_C)
+func CImplFuncRenamed_Swift(arg: CInt) {
+  // OK
+}
+
+@implementation(BadCategory) @cdecl
+func CImplFunc2(_: Int32) {
+  // expected-error@-2 {{global function 'CImplFunc2' does not belong to an Objective-C category; remove the category name from this attribute}} {{16-29=}}
+}
+
+@implementation @cdecl
+func CImplFuncMissing(_: Int32) {
+  // expected-error@-2 {{could not find imported function 'CImplFuncMissing' matching global function 'CImplFuncMissing'; make sure your umbrella or bridging header imports the header that declares it}}
+}
+
+@implementation @cdecl
+func CImplFuncMismatch1(_: Float) {
+  // expected-error@-1 {{global function 'CImplFuncMismatch1' of type '(Float) -> ()' does not match type '(Int32) -> Void' declared by the header}}
+}
+
+@implementation @cdecl
+func CImplFuncMismatch2(_: Int32) -> Float {
+  // expected-error@-1 {{global function 'CImplFuncMismatch2' of type '(Int32) -> Float' does not match type '(Int32) -> Void' declared by the header}}
+}
+
+@implementation @cdecl(CImplFuncNameMismatch1)
+func mismatchedName1(_: Int32) {
+  // expected-error@-2 {{could not find imported function 'CImplFuncNameMismatch1' matching global function 'mismatchedName1'; make sure your umbrella or bridging header imports the header that declares it}}
+  // FIXME: Improve diagnostic for a partial match.
+}
+
+@implementation @cdecl(mismatchedName2)
+func CImplFuncNameMismatch2(_: Int32) {
+  // expected-error@-2 {{could not find imported function 'mismatchedName2' matching global function 'CImplFuncNameMismatch2'; make sure your umbrella or bridging header imports the header that declares it}}
+  // FIXME: Improve diagnostic for a partial match.
+}
+
+//
+// TODO: @cdecl for global functions imported as computed vars
+//
+var cImplComputedGlobal1: Int32 {
+  @implementation @cdecl(CImplGetComputedGlobal1)
+  get {
+    // FIXME: Lookup for vars isn't working yet
+    // expected-error@-3 {{could not find imported function 'CImplGetComputedGlobal1' matching getter for var 'cImplComputedGlobal1'; make sure your umbrella or bridging header imports the header that declares it}}
+    return 0
+  }
+
+  @implementation @cdecl(CImplSetComputedGlobal1)
+  set {
+    // FIXME: Lookup for vars isn't working yet
+    // expected-error@-3 {{could not find imported function 'CImplSetComputedGlobal1' matching setter for var 'cImplComputedGlobal1'; make sure your umbrella or bridging header imports the header that declares it}}
+    print(newValue)
+  }
+}
+
+//
+// TODO: @cdecl for import-as-member functions
+//
+extension CImplStruct {
+  @implementation @cdecl(CImplStructStaticFunc1)
+  static func staticFunc1(_: Int32) {
+    // FIXME: Add underlying support for this
+    // expected-error@-3 {{@cdecl can only be applied to global functions}}
+    // FIXME: Lookup in an enclosing type is not working yet
+    // expected-error@-5 {{could not find imported function 'CImplStructStaticFunc1' matching static method 'staticFunc1'; make sure your umbrella or bridging header imports the header that declares it}}
+  }
+}