[cxx-interop][test] add %check-interop-cxx-header-in-clang test command substitution to parse and validated generated C++ header in multiple C++ language modes

This ensures that we validate C++14, C++17, and C++20

Author: hyp

test/Interop/SwiftToCxx/functions/cdecl.swift

@@ -1,9 +1,8 @@
 // RUN: %empty-directory(%t)
-// RUN: %target-swift-frontend %s -typecheck -module-name CdeclFunctions -emit-cxx-header-path %t/empty.h
-// RUN: %FileCheck %s < %t/empty.h
+// RUN: %target-swift-frontend %s -typecheck -module-name CdeclFunctions -emit-cxx-header-path %t/cdecl.h
+// RUN: %FileCheck %s < %t/cdecl.h
 
-// RUN: %check-cxx-header-in-clang -std=c++14 %t/empty.h
-// RUN: %check-cxx-header-in-clang -std=c++17 %t/empty.h
+// RUN: %check-interop-cxx-header-in-clang(%t/cdecl.h)
 
 // CHECK-LABEL: namespace CdeclFunctions {
 

test/Interop/SwiftToCxx/functions/function-availability.swift

@@ -2,8 +2,7 @@
 // RUN: %target-swift-frontend %s -typecheck -module-name Functions -emit-cxx-header-path %t/functions.h
 // RUN: %FileCheck %s < %t/functions.h
 
-// RUN: %check-cxx-header-in-clang -std=c++14 %t/functions.h
-// RUN: %check-cxx-header-in-clang -std=c++17 %t/functions.h
+// RUN: %check-interop-cxx-header-in-clang(%t/functions.h)
 
 // CHECK-LABEL: namespace Functions {
 

test/Interop/SwiftToCxx/functions/swift-functions.swift

@@ -2,8 +2,7 @@
 // RUN: %target-swift-frontend %s -typecheck -module-name Functions -emit-cxx-header-path %t/functions.h
 // RUN: %FileCheck %s < %t/functions.h
 
-// RUN: %check-cxx-header-in-clang -std=c++14 %t/functions.h
-// RUN: %check-cxx-header-in-clang -std=c++17 %t/functions.h
+// RUN: %check-interop-cxx-header-in-clang(%t/functions.h)
 
 // CHECK-LABEL: namespace Functions {
 

test/Interop/SwiftToCxx/module/module-to-namespace.swift

@@ -2,8 +2,7 @@
 // RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) %s -typecheck -module-name Test -emit-cxx-header-path %t/empty.h
 // RUN: %FileCheck %s < %t/empty.h
 
-// RUN: %check-cxx-header-in-clang -std=c++14 %t/empty.h
-// RUN: %check-cxx-header-in-clang -std=c++17 %t/empty.h
+// RUN: %check-interop-cxx-header-in-clang(%t/empty.h)
 
 // CHECK-LABEL: namespace Test {
 // CHECK:       } // namespace Test

test/Interop/lit.local.cfg

@@ -22,3 +22,9 @@ config.substitutions.insert(0, ('%target-interop-build-swift',
                                 '%target-build-swift -Xfrontend -enable-cxx-interop '))
 # Build C++ files with matching link settings, if required by the target.
 config.substitutions.insert(0, ('%target-interop-build-clangxx', '%target-clangxx ' + clang_opt))
+
+# Test parsing of the generated C++ header in different C++ language modes.
+config.substitutions.insert(0, ('%check-interop-cxx-header-in-clang\(([^)]+)\)',
+                             SubstituteCaptures(r'%check-cxx-header-in-clang -std=c++14 \1 && '
+                                                r'%check-cxx-header-in-clang -std=c++17 \1 && '
+                                                r'%check-cxx-header-in-clang -std=c++20 \1')))