Bug 1217099 - Stop emitting pointless JSOP_GETLOCAL; JSOP_POP bytecode sequence for `var x;`. r=shu.

--HG--
extra : commitid : CZL288j5vAL
extra : rebase_source : c5b484323f9a17d7794e23b863a77a9bd7b739ce

devtools/server/tests/unit/test_get-executable-lines.js

@@ -38,7 +38,7 @@ function test_executable_lines() {
       do_check_true(!error);
       let source = gThreadClient.source(sources[0]);
       source.getExecutableLines(function(lines){
-        do_check_true(arrays_equal([2, 3, 5, 6, 7, 8, 12, 14, 16], lines));
+        do_check_true(arrays_equal([2, 5, 7, 8, 12, 14, 16], lines));
         finishClient(gClient);
       });
     });

js/src/frontend/BytecodeEmitter.cpp

@@ -4355,6 +4355,9 @@ BytecodeEmitter::emitSingleVariable(ParseNode* pn, ParseNode* binding, ParseNode
         MOZ_ASSERT(emitOption != DefineVars);
         if (!emit1(JSOP_UNDEFINED))
             return false;
+    } else {
+        // The declaration is like `var x;`. Nothing to do.
+        return true;
     }
 
     // If we are not initializing, nothing to pop. If we are initializing

js/src/jit-test/tests/debug/Script-getAllColumnOffsets-02.js

@@ -18,4 +18,4 @@ global.eval("function f(n){var w0,x1=3,y2=4,z3=9} debugger;");
 global.f(3);
 
 // Should have hit each variable declared.
-assertEq(global.log, "18 21 26 31 35 ");
+assertEq(global.log, "21 26 31 35 ");

js/src/tests/ecma_5/Global/bug-320887.js

@@ -0,0 +1,15 @@
+// `var x` should not call the getter of an existing global property.
+
+var hit = 0;
+Object.defineProperty(this, "x", {
+    get: function () { return ++hit; },
+    configurable: true
+});
+eval("var x;");
+assertEq(hit, 0);
+
+// The declaration should not have redefined the global x, either.
+assertEq(x, 1);
+assertEq(x, 2);
+
+reportCompare(0, 0);