Macros: Escape init when printing names for attached macros.

Older compilers can't parse `name(init)`. Restore the call to
`escapeKeywordInContext()` to ensure special names get escaped.

Resolves rdar://108806697

Author: tshortli

lib/AST/Attr.cpp

@@ -1376,7 +1376,9 @@ bool DeclAttribute::printImpl(ASTPrinter &Printer, const PrintOptions &Options,
             if (macroIntroducedNameRequiresArgument(name.getKind())) {
               SmallString<32> buffer;
               StringRef nameText = name.getName().getString(buffer);
-              bool shouldEscape = nameText == "$";
+              bool shouldEscape =
+                  escapeKeywordInContext(nameText, PrintNameContext::Normal) ||
+                  nameText == "$";
               Printer << "(";
               if (shouldEscape)
                 Printer << "`";

test/ModuleInterface/macros.swift

@@ -35,7 +35,7 @@
 @attached(accessor) public macro myWrapper() = #externalMacro(module: "SomeModule", type: "Wrapper")
 
 // CHECK: #if compiler(>=5.3) && $Macros && $AttachedMacros
-// CHECK: @attached(member, names: named(init), prefixed(`$`)) public macro MemberwiseInit() -> () = #externalMacro(module: "SomeModule", type: "MemberwiseInitMacro")
+// CHECK: @attached(member, names: named(`init`), prefixed(`$`)) public macro MemberwiseInit() -> () = #externalMacro(module: "SomeModule", type: "MemberwiseInitMacro")
 // CHECK-NEXT: #endif
 @attached(member, names: named(init), prefixed(`$`)) public macro MemberwiseInit() -> () = #externalMacro(module: "SomeModule", type: "MemberwiseInitMacro")