[ASTPrint] Print documentation comments for extensions and subscripts.

Author: akyrtzi

lib/AST/ASTPrinter.cpp

@@ -1263,6 +1263,7 @@ void PrintAST::visitImportDecl(ImportDecl *decl) {
 }
 
 void PrintAST::visitExtensionDecl(ExtensionDecl *decl) {
+  printDocumentationComment(decl);
   printAttributes(decl);
   Printer << "extension ";
   recordDeclLoc(decl,
@@ -1922,6 +1923,7 @@ void PrintAST::visitEnumElementDecl(EnumElementDecl *decl) {
 }
 
 void PrintAST::visitSubscriptDecl(SubscriptDecl *decl) {
+  printDocumentationComment(decl);
   printAttributes(decl);
   printAccessibility(decl);
   recordDeclLoc(decl,

lib/AST/RawComment.cpp

@@ -69,7 +69,7 @@ SingleRawComment::SingleRawComment(StringRef RawText, unsigned StartColumn)
 
 static bool canHaveComment(const Decl *D) {
   return !D->hasClangNode() &&
-         isa<ValueDecl>(D) &&
+         (isa<ValueDecl>(D) || isa<ExtensionDecl>(D)) &&
          !isa<ParamDecl>(D) &&
          (!isa<AbstractTypeParamDecl>(D) || isa<AssociatedTypeDecl>(D));
 }

test/IDE/print_source_file_interface_2.swift

@@ -9,5 +9,12 @@ public class MyClass {
   func doit(x: Int) {}
 }
 
+/// This is a very nice extension.
+extension MyClass {
+
+  /// and a nice subscript.
+  subscript(i: Int) -> Int { return 0 }
+}
+
 // RUN: %target-swift-ide-test -print-swift-file-interface -source-filename %s > %t.out
 // RUN: diff -u %s.result %t.out

test/IDE/print_source_file_interface_2.swift.result

@@ -10,3 +10,10 @@ public class MyClass {
 
     internal func doit(x: Int)
 }
+
+/// This is a very nice extension.
+extension MyClass {
+
+    /// and a nice subscript.
+    internal subscript (i: Int) -> Int { get }
+}