Compile time error if name is used before variable is declared

runtime/vm/parser.cc

Index: runtime/vm/parser.cc
===================================================================
--- runtime/vm/parser.cc	(revision 29679)
+++ runtime/vm/parser.cc	(working copy)
@@ -5260,10 +5260,27 @@
   TRACE_PARSER("ParseVariableDeclaration");
   ASSERT(IsIdentifier());
   const intptr_t ident_pos = TokenPos();
-  LocalVariable* variable =
-      new LocalVariable(ident_pos, *CurrentLiteral(), type);
+  const String& ident = *CurrentLiteral();
+  LocalVariable* variable = new LocalVariable(ident_pos, ident, type);
   ASSERT(current_block_ != NULL);
   ASSERT(current_block_->scope != NULL);
+  const intptr_t previous_pos =
+      current_block_->scope->PreviousReferencePos(ident);
+  if (previous_pos >= 0) {
+    ASSERT(!script_.IsNull());
+    if (script_.HasSource()) {
+      intptr_t line_number;
+      script_.GetTokenLocation(previous_pos, &line_number, NULL);

[Ivan Posva, 2013/11/01 16:35:12]

Since we are only getting the line number here we should not need to make the
distinction whether we have source or not.

[hausner, 2013/11/01 16:42:51]

True. I figured line numbers make less sense if a user has no access to the
source code. Removed the distinction.

+      ErrorMsg(ident_pos,
+               "identifier '%s' previously used in line %" Pd "",
+               ident.ToCString(),
+               line_number);
+    } else {
+      ErrorMsg(ident_pos,
+               "identifier '%s' previously used in this scope",
+               ident.ToCString());
+    }
+  }
   ConsumeToken();  // Variable identifier.
   AstNode* initialization = NULL;
   if (CurrentToken() == Token::kASSIGN) {
@@ -8776,6 +8793,9 @@
   TRACE_PARSER("ResolveIdentInLocalScope");
   // First try to find the identifier in the nested local scopes.
   LocalVariable* local = LookupLocalScope(ident);
+  if (current_block_ != NULL) {
+    current_block_->scope->AddReferencedName(ident_pos, ident);
+  }
   if (local != NULL) {
     if (node != NULL) {
       if (local->IsConst()) {
@@ -9120,6 +9140,11 @@
   }
   QualIdent type_name;
   if (finalization == ClassFinalizer::kIgnore) {
+    if (!is_top_level_ && (current_block_ != NULL)) {
+      // Add the library prefix or type class name to the list of referenced
+      // names of this scope, even if the type is ignored.
+      current_block_->scope->AddReferencedName(TokenPos(), *CurrentLiteral());
+    }
     SkipQualIdent();
   } else {
     ParseQualIdent(&type_name);