Bug 918828, part 2 - Update decompiler for JSOP_SYMBOL. This improves error messages when @@iterator is called implicitly. r=Waldo.

--HG--
extra : rebase_source : e0e00a4d203f3a2c8a4d7cfa0a53d389e16fec53

js/src/jsatom.cpp

@@ -156,7 +156,7 @@ 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

@@ -1592,6 +1592,13 @@ 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_5/extensions/decompile-for-of.js

@@ -0,0 +1,28 @@
+// 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;
+    }
+
+    var ITERATOR = JS_HAS_SYMBOLS ? "Symbol.iterator" : "'@@iterator'";
+    assertEq(s, `x[${ITERATOR}] is not a function`);
+}
+
+x = {};
+check("for (var v of x) throw fit;");
+check("[...x]");
+check("Math.hypot(...x)");
+
+x[std_iterator] = "potato";
+check("for (var v of x) throw fit;");
+
+x[std_iterator] = {};
+check("for (var v of x) throw fit;");
+
+if (typeof reportCompare === "function")
+    reportCompare(0, 0, "ok");

js/src/vm/Runtime.h

@@ -406,6 +406,10 @@ 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 {