Slight optimization of case clause type checks

runtime/vm/parser.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/parser.h"
 
 #include "lib/invocation_mirror.h"
 #include "vm/bigint_operations.h"
 #include "vm/bootstrap.h"
 #include "vm/class_finalizer.h"
@@ skipping 6063 matching lines @@
     }
     if (first_value.IsDouble()) {
       if (!val.IsDouble()) {
         ErrorMsg(val_pos, "expected case expression of type double");
       }
       continue;
     }
     if (val.clazz() != first_value.clazz()) {
       ErrorMsg(val_pos, "all case expressions must be of same type");
     }
-    Class& cls = Class::Handle(val.clazz());
-    const Function& equal_op = Function::Handle(
-        Resolver::ResolveDynamicAnyArgs(cls, Symbols::EqualOperator()));
-    ASSERT(!equal_op.IsNull());
-    cls = equal_op.Owner();
-    if (!cls.IsObjectClass()) {
-      ErrorMsg(val_pos,
-               "type class of case expression must not implement operator ==");
+    if (i == 0) {
+      // The value is of some type other than int, String or double.
+      // Check that the type class does not override the == operator.
+      // Check this only in the first loop iteration since all values
+      // are of the same type, which we check above.
+      Class& cls = Class::Handle(val.clazz());
+      const Function& equal_op = Function::Handle(
+          Resolver::ResolveDynamicAnyArgs(cls, Symbols::EqualOperator()));
+      ASSERT(!equal_op.IsNull());
+      cls = equal_op.Owner();
+      if (!cls.IsObjectClass()) {
+        ErrorMsg(val_pos,
+            "type class of case expression must not implement operator ==");
+      }
     }
   }
 }
 
 
 CaseNode* Parser::ParseCaseClause(LocalVariable* switch_expr_value,
                                   GrowableArray<LiteralNode*>* case_expr_values,
                                   SourceLabel* case_label) {
   TRACE_PARSER("ParseCaseClause");
   bool default_seen = false;
@@ skipping 4501 matching lines @@
 void Parser::SkipQualIdent() {
   ASSERT(IsIdentifier());
   ConsumeToken();
   if (CurrentToken() == Token::kPERIOD) {
     ConsumeToken();  // Consume the kPERIOD token.
     ExpectIdentifier("identifier expected after '.'");
   }
 }
 
 }  // namespace dart