Bug 918828, part 3 - Update decompiler for JSOP_SYMBOL. This improves error messages when @@iterator is called implicitly. r=Waldo.

--HG--
extra : rebase_source : b9edaa7be12bdfde40b38d3f413f10624c4f0dcf

js/src/jit-test/tests/basic/expression-autopsy.js

@@ -109,8 +109,8 @@ check("o[- (o)]");
 // A few one off tests
 check_one("6", (function () { 6() }), " is not a function");
 check_one("Array.prototype.reverse.call(...)", (function () { Array.prototype.reverse.call('123'); }), " is read-only");
-check_one("(intermediate value)[(intermediate value)](...).next(...).value", function () { var [{ x }] = [null, {}]; }, " is null");
-check_one("(intermediate value)[(intermediate value)](...).next(...).value", function () { ieval("let (x) { var [a, b, [c0, c1]] = [x, x, x]; }") }, " is undefined");
+check_one("(intermediate value)[Symbol.iterator](...).next(...).value", function () { var [{ x }] = [null, {}]; }, " is null");
+check_one("(intermediate value)[Symbol.iterator](...).next(...).value", function () { ieval("let (x) { var [a, b, [c0, c1]] = [x, x, x]; }") }, " is undefined");
 
 // Check fallback behavior
 assertThrowsInstanceOf(function () { for (let x of undefined) {} }, TypeError);

js/src/jsatom.cpp

@@ -157,7 +157,7 @@ JSRuntime::initializeAtoms(JSContext *cx)
     if (!wellKnownSymbols)
         return false;
 
-    ImmutablePropertyNamePtr *descriptions = &commonNames->Symbol_iterator;
+    ImmutablePropertyNamePtr *descriptions = commonNames->wellKnownSymbolDescriptions();
     ImmutableSymbolPtr *symbols = reinterpret_cast<ImmutableSymbolPtr *>(wellKnownSymbols);
     for (size_t i = 0; i < JS::WellKnownSymbolLimit; i++) {
         JS::Symbol *symbol = JS::Symbol::new_(cx, JS::SymbolCode(i), descriptions[i]);

js/src/jsopcode.cpp

@@ -1540,6 +1540,13 @@ ExpressionDecompiler::decompilePC(jsbytecode *pc)
         return sprinter.printf("%d", GetBytecodeInteger(pc)) >= 0;
       case JSOP_STRING:
         return quote(loadAtom(pc), '"');
+      case JSOP_SYMBOL: {
+        unsigned i = uint8_t(pc[1]);
+        MOZ_ASSERT(i < JS::WellKnownSymbolLimit);
+        if (i < JS::WellKnownSymbolLimit)
+            return write(cx->names().wellKnownSymbolDescriptions()[i]);
+        break;
+      }
       case JSOP_UNDEFINED:
         return write(js_undefined_str);
       case JSOP_THIS:

js/src/tests/js1_8/regress/regress-469625-03.js

@@ -26,7 +26,7 @@ function test()
     var [a, b, [c0, c1]] = [x, x, x];
   }
 
-  expect = 'TypeError: (intermediate value)[(intermediate value)](...).next(...).value is null';
+  expect = 'TypeError: (intermediate value)[Symbol.iterator](...).next(...).value is null';
   actual = 'No Error';
   try
   {

js/src/tests/js1_8_5/extensions/decompile-for-of.js

@@ -0,0 +1,26 @@
+// The decompiler can handle the implicit call to @@iterator in a for-of loop.
+
+var x;
+function check(code) {
+    var s = "no exception thrown";
+    try {
+        eval(code);
+    } catch (exc) {
+        s = exc.message;
+    }
+    assertEq(s, "x[Symbol.iterator] is not a function");
+}
+
+x = {};
+check("for (var v of x) throw fit;");
+check("[...x]");
+check("Math.hypot(...x)");
+
+x[Symbol.iterator] = "potato";
+check("for (var v of x) throw fit;");
+
+x[Symbol.iterator] = {};
+check("for (var v of x) throw fit;");
+
+if (typeof reportCompare === "function")
+    reportCompare(0, 0, "ok");

js/src/vm/Runtime.h

@@ -400,6 +400,10 @@ struct JSAtomState
 #define PROPERTYNAME_FIELD(name, code, init, clasp) js::ImmutablePropertyNamePtr name;
     JS_FOR_EACH_PROTOTYPE(PROPERTYNAME_FIELD)
 #undef PROPERTYNAME_FIELD
+
+    js::ImmutablePropertyNamePtr *wellKnownSymbolDescriptions() {
+        return &Symbol_iterator;
+    }
 };
 
 namespace js {