Remove some duplication in code that extracts the source for a function.

runtime/vm/object.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/object.h"
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/assembler.h"
 #include "vm/cpu.h"
@@ skipping 6580 matching lines @@
     } else {
       tmp = cls.UserVisibleName();
     }
   }
   tmp = String::Concat(tmp, Symbols::Dot());
   const String& suffix = String::Handle(UserVisibleName());
   return String::Concat(tmp, suffix);
 }
 
 
-RawString* Function::GetSource() {
+RawString* Function::GetSource() const {
+  if (IsImplicitConstructor() || IsSignatureFunction()) {
+    // We may need to handle more cases when the restrictions on mixins are
+    // relaxed. In particular we might start associating some source with the
+    // forwarding constructors when it becomes possible to specify a particular
+    // constructor from the mixin to use.
+    return String::null();
+  }
   const Script& func_script = Script::Handle(script());
-  // Without the + 1 the final "}" is not included.
-  return func_script.GetSnippet(token_pos(), end_token_pos() + 1);
+  const TokenStream& stream = TokenStream::Handle(func_script.tokens());
+  if (!func_script.HasSource()) {
+    // When source is not available, avoid printing the whole token stream and
+    // doing expensive position calculations.
+    return stream.GenerateSource(token_pos(), end_token_pos() + 1);
+  }
+
+  const TokenStream::Iterator tkit(stream, end_token_pos());
+  intptr_t from_line;
+  intptr_t from_col;
+  intptr_t to_line;
+  intptr_t to_col;
+  func_script.GetTokenLocation(token_pos(), &from_line, &from_col);
+  func_script.GetTokenLocation(end_token_pos(), &to_line, &to_col);
+  intptr_t last_tok_len = String::Handle(tkit.CurrentLiteral()).Length();
+  // Handle special cases for end tokens of closures (where we exclude the last
+  // token):
+  // (1) "foo(() => null, bar);": End token is `,', but we don't print it.
+  // (2) "foo(() => null);": End token is ')`, but we don't print it.
+  // (3) "var foo = () => null;": End token is `;', but in this case the token
+  // semicolon belongs to the assignment so we skip it.
+  if ((tkit.CurrentTokenKind() == Token::kCOMMA) ||                   // Case 1.
+      (tkit.CurrentTokenKind() == Token::kRPAREN) ||                  // Case 2.
+      (tkit.CurrentTokenKind() == Token::kSEMICOLON &&
+       String::Handle(name()).Equals("<anonymous closure>"))) {  // Case 3.
+    last_tok_len = 0;
+  }
+  const String& result = String::Handle(func_script.GetSnippet(
+      from_line, from_col, to_line, to_col + last_tok_len));
+  ASSERT(!result.IsNull());
+  return result.raw();
 }
 
 
 // Construct fingerprint from token stream. The token stream contains also
 // arguments.
 int32_t Function::SourceFingerprint() const {
   uint32_t result = IsImplicitClosureFunction()
       ? String::Handle(Function::Handle(parent_function()).Signature()).Hash()
       : String::Handle(Signature()).Hash();
   TokenStream::Iterator tokens_iterator(TokenStream::Handle(
@@ skipping 1779 matching lines @@
   if (line_start_idx >= 0) {
     return String::SubString(src,
                              line_start_idx,
                              last_char_idx - line_start_idx + 1);
   } else {
     return Symbols::Empty().raw();
   }
 }
 
 
-RawString* Script::GetSnippet(intptr_t from_token_pos,
-                              intptr_t to_token_pos) const {
-  intptr_t from_line, from_column;
-  intptr_t to_line, to_column;
-  GetTokenLocation(from_token_pos, &from_line, &from_column);
-  GetTokenLocation(to_token_pos, &to_line, &to_column);
-  return GetSnippet(from_line, from_column, to_line, to_column);
-}
-
-
 RawString* Script::GetSnippet(intptr_t from_line,
                               intptr_t from_column,
                               intptr_t to_line,
                               intptr_t to_column) const {
   const String& src = String::Handle(Source());
   intptr_t length = src.Length();
   intptr_t line = 1 + line_offset();
   intptr_t column = 1;
   intptr_t scan_position = 0;
   intptr_t snippet_start = -1;
@@ skipping 12301 matching lines @@
   return tag_label.ToCString();
 }
 
 
 void UserTag::PrintJSONImpl(JSONStream* stream, bool ref) const {
   Instance::PrintJSONImpl(stream, ref);
 }
 
 
 }  // namespace dart