Restrict yield outside generators in strict mode

* Move some yield/generic tests from compress/harmony.js to
  compress/yield.js
 * Adjust error messages to conform ecmascript standards

lib/parse.js

@@ -795,14 +795,14 @@ function parse($TEXT, options) {
     function unexpected(token) {
         if (token == null)
             token = S.token;
-        token_error(token, "Unexpected token: " + token.type + " (" + token.value + ")");
+        token_error(token, "SyntaxError: Unexpected token: " + token.type + " (" + token.value + ")");
     };
 
     function expect_token(type, val) {
         if (is(type, val)) {
             return next();
         }
-        token_error(S.token, "Unexpected token " + S.token.type + " «" + S.token.value + "»" + ", expected " + type + " «" + val + "»");
+        token_error(S.token, "SyntaxError: Unexpected token " + S.token.type + " «" + S.token.value + "»" + ", expected " + type + " «" + val + "»");
     };
 
     function expect(punc) { return expect_token("punc", punc); };
@@ -993,7 +993,7 @@ function parse($TEXT, options) {
         var label = as_symbol(AST_Label);
         if (label.name === "yield" && is_in_generator()) {
             // Ecma-262, 12.1.1 Static Semantics: Early Errors
-            croak("Yield cannot be used as label inside generators");
+            token_error(S.prev, "SyntaxError: Yield cannot be used as label inside generators");
         }
         if (find_if(function(l){ return l.name == label.name }, S.labels)) {
             // ECMA-262, 12.12: An ECMAScript program is considered
@@ -1873,9 +1873,12 @@ function parse($TEXT, options) {
                 expect("]");
                 return ex;
             } else unexpected();
-          case "num":
-          case "string":
           case "name":
+            if (tmp.value === "yield" && S.input.has_directive("use strict") && !is_in_generator()) {
+                token_error(tmp, "SyntaxError: Unexpected yield identifier inside strict mode");
+            }
+          case "string":
+          case "num":
           case "operator":
           case "keyword":
           case "atom":
@@ -1915,6 +1918,9 @@ function parse($TEXT, options) {
             if (!noerror) croak("Name expected");
             return null;
         }
+        if (is("name", "yield") && S.input.has_directive("use strict")) {
+            token_error(S.prev, "SyntaxError: Unexpected yield identifier inside strict mode");
+        }
         var sym = _make_symbol(type);
         next();
         return sym;
@@ -2050,9 +2056,13 @@ function parse($TEXT, options) {
     var maybe_assign = function(no_in) {
         var start = S.token;
 
-        if (start.type == "name" && start.value == "yield" && is_in_generator()) {
+        if (start.type == "name" && start.value == "yield") {
+            if (is_in_generator()) {
                 next();
                 return _yield_expression();
+            } else if (S.input.has_directive("use strict")) {
+                token_error(S.token, "SyntaxError: Unexpected yield identifier inside strict mode")
+            }
         }
 
         if (start.type == "punc" && start.value == "(" && peek().value == ")") {

test/compress/harmony.js

@@ -450,109 +450,3 @@ regression_cannot_use_of: {
         foo();  /* Label statement missing? No prob. */
     }
 }
-
-generators: {
-    input: {
-        function* fn() {};
-    }
-    expect_exact: "function*fn(){}"
-}
-
-generators_yield: {
-    input: {
-      function* fn() {
-        yield remote();
-      }
-    }
-    expect_exact: "function*fn(){yield remote()}"
-}
-
-generators_yield_assign: {
-    input: {
-      function* fn() {
-          var x = {};
-          x.prop = yield 5;
-      }
-    }
-    expect_exact: "function*fn(){var x={};x.prop=yield 5}"
-}
-
-generator_yield_undefined: {
-    input: {
-        function* fn() {
-            yield;
-        }
-    }
-    expect_exact: "function*fn(){yield}"
-}
-
-yield_optimize_expression: {
-    options = {
-    }
-    input: {
-        function* f1() { yield; }
-        function* f2() { yield undefined; }
-        function* f3() { yield null; }
-        function* f4() { yield* undefined; }
-    }
-    expect: {
-        function* f1() { yield }
-        function* f2() { yield; }
-        function* f3() { yield null; }
-        function* f4() { yield* void 0; }
-    }
-}
-
-yield_statements: {
-    input: {
-        function* fn() {
-            var a = (yield 1) + (yield 2);
-            var b = (yield 3) === (yield 4);
-            var c = (yield 5) << (yield 6);
-            var d = yield 7;
-            var e = (yield 8) ? yield 9 : yield 10;
-            var f = -(yield 11);
-        }
-    }
-    expect_exact: "function*fn(){var a=(yield 1)+(yield 2);var b=(yield 3)===(yield 4);var c=(yield 5)<<(yield 6);var d=yield 7;var e=(yield 8)?yield 9:yield 10;var f=-(yield 11)}"
-}
-
-yield_as_identifier_in_function_in_generator: {
-    input: {
-        var g = function*() {
-            function h() {
-                yield = 1;
-            }
-        };
-    }
-    expect: {
-        var g = function*() {
-            function h() {
-                yield = 1;
-            }
-        };
-    }
-}
-
-yield_before_punctuators: {
-    input: {
-        iter = (function*() {
-            assignmentResult = [ x = yield ] = value;
-        })();
-        function* g1() { (yield) }
-        function* g2() { [yield] }
-        function* g3() { return {yield} } // Added return to avoid {} drop
-        function* g4() { yield, yield; }
-        function* g5() { (yield) ? yield : yield; }
-    }
-    expect: {
-        iter = (function*() {
-            assignmentResult = [ x = yield ] = value;
-        })();
-        function* g1() { (yield) }
-        function* g2() { [yield] }
-        function* g3() { return {yield} }
-        function* g4() { yield, yield; }
-        function* g5() { (yield) ? yield : yield; }
-    }
-}

test/compress/yield.js

@@ -0,0 +1,142 @@
+generators: {
+    input: {
+        function* fn() {};
+    }
+    expect_exact: "function*fn(){}"
+}
+
+generators_yield: {
+    input: {
+      function* fn() {
+        yield remote();
+      }
+    }
+    expect_exact: "function*fn(){yield remote()}"
+}
+
+generators_yield_assign: {
+    input: {
+      function* fn() {
+          var x = {};
+          x.prop = yield 5;
+      }
+    }
+    expect_exact: "function*fn(){var x={};x.prop=yield 5}"
+}
+
+generator_yield_undefined: {
+    input: {
+        function* fn() {
+            yield;
+        }
+    }
+    expect_exact: "function*fn(){yield}"
+}
+
+yield_optimize_expression: {
+    options = {
+    }
+    input: {
+        function* f1() { yield; }
+        function* f2() { yield undefined; }
+        function* f3() { yield null; }
+        function* f4() { yield* undefined; }
+    }
+    expect: {
+        function* f1() { yield }
+        function* f2() { yield; }
+        function* f3() { yield null; }
+        function* f4() { yield* void 0; }
+    }
+}
+
+yield_statements: {
+    input: {
+        function* fn() {
+            var a = (yield 1) + (yield 2);
+            var b = (yield 3) === (yield 4);
+            var c = (yield 5) << (yield 6);
+            var d = yield 7;
+            var e = (yield 8) ? yield 9 : yield 10;
+            var f = -(yield 11);
+        }
+    }
+    expect_exact: "function*fn(){var a=(yield 1)+(yield 2);var b=(yield 3)===(yield 4);var c=(yield 5)<<(yield 6);var d=yield 7;var e=(yield 8)?yield 9:yield 10;var f=-(yield 11)}"
+}
+
+yield_as_identifier_in_function_in_generator: {
+    input: {
+        var g = function*() {
+            function h() {
+                yield = 1;
+            }
+        };
+    }
+    expect: {
+        var g = function*() {
+            function h() {
+                yield = 1;
+            }
+        };
+    }
+}
+
+yield_before_punctuators: {
+    input: {
+        iter = (function*() {
+            assignmentResult = [ x = yield ] = value;
+        })();
+        function* g1() { (yield) }
+        function* g2() { [yield] }
+        function* g3() { return {yield} } // Added return to avoid {} drop
+        function* g4() { yield, yield; }
+        function* g5() { (yield) ? yield : yield; }
+    }
+    expect: {
+        iter = (function*() {
+            assignmentResult = [ x = yield ] = value;
+        })();
+        function* g1() { (yield) }
+        function* g2() { [yield] }
+        function* g3() { return {yield} }
+        function* g4() { yield, yield; }
+        function* g5() { (yield) ? yield : yield; }
+    }
+}
+
+yield_as_identifier_outside_strict_mode: {
+    input: {
+        import yield from "bar";
+        yield = 123;
+        while (true) {
+            yield:
+            for(;;) break yield;
+
+            foo();
+        }
+        while (true)
+            yield: for(;;) continue yield;
+        function yield(){}
+        function foo(...yield){}
+        try { new Error("") } catch (yield) {}
+        var yield = "foo";
+        class yield {}
+    }
+    expect: {
+        import yield from "bar";
+        yield = 123;
+        while (true) {
+            yield:
+            for(;;) break yield;
+
+            foo();
+        }
+        while (true)
+            yield: for(;;) continue yield;
+        function yield(){}
+        function foo(...yield){}
+        try { new Error("") } catch (yield) {}
+        var yield = "foo";
+        class yield {}
+    }
+}

test/mocha/arrow.js

@@ -15,7 +15,7 @@ describe("Arrow functions", function() {
         }
         var error = function(e) {
             return e instanceof uglify.JS_Parse_Error &&
-                e.message === "Unexpected token: expand (...)";
+                e.message === "SyntaxError: Unexpected token: expand (...)";
         }
 
         for (var i = 0; i < tests.length; i++) {

test/mocha/class.js

@@ -16,7 +16,7 @@ describe("Class", function() {
         }
         var error = function(e) {
             return e instanceof uglify.JS_Parse_Error &&
-                e.message === "Unexpected token: expand (...)";
+                e.message === "SyntaxError: Unexpected token: expand (...)";
         }
 
         for (var i = 0; i < tests.length; i++) {

test/mocha/function.js

@@ -20,7 +20,7 @@ describe("Function", function() {
         }
         var error = function(e) {
             return e instanceof uglify.JS_Parse_Error &&
-                e.message === "Unexpected token: expand (...)";
+                e.message === "SyntaxError: Unexpected token: expand (...)";
         }
 
         for (var i = 0; i < tests.length; i++) {

test/mocha/yield.js

@@ -15,7 +15,7 @@ describe("Yield", function() {
         }
         var expect = function(e) {
             return e instanceof UglifyJS.JS_Parse_Error &&
-                e.message === "Yield cannot be used as label inside generators";
+                e.message === "SyntaxError: Yield cannot be used as label inside generators";
         }
         assert.throws(test, expect);
     });
@@ -27,7 +27,7 @@ describe("Yield", function() {
         }
         var expect = function(e) {
             return e instanceof UglifyJS.JS_Parse_Error &&
-                e.message === "Unexpected token: punc (;)";
+                e.message === "SyntaxError: Unexpected token: punc (;)";
         }
         assert.throws(test, expect);
     });
@@ -39,7 +39,7 @@ describe("Yield", function() {
         }
         var expect = function(e) {
             return e instanceof UglifyJS.JS_Parse_Error &&
-                e.message === "Unexpected token: operator (*)";
+                e.message === "SyntaxError: Unexpected token: operator (*)";
         }
         assert.throws(test, expect);
     });
@@ -64,4 +64,43 @@ describe("Yield", function() {
             "function*f(){yield,yield,yield*void 0,yield}"
         );
     });
+
+    it("Should not allow yield to be used as symbol, identifier or property outside generators in strict mode", function() {
+        var tests = [
+            // Fail as as_symbol
+            '"use strict"; import yield from "bar";',
+            '"use strict"; yield = 123;',
+            '"use strict"; yield: "123";',
+            '"use strict"; for(;;){break yield;}',
+            '"use strict"; for(;;){continue yield;}',
+            '"use strict"; function yield(){}',
+            '"use strict"; function foo(...yield){}',
+            '"use strict"; try { new Error("")} catch (yield) {}',
+            '"use strict"; var yield = "foo";',
+            '"use strict"; class yield {}',
+
+            // Fail as maybe_assign
+            '"use strict"; var foo = yield;',
+            '"use strict"; var foo = bar = yield',
+
+            // Fail as as_property_name
+            '"use strict"; var foo = {yield};',
+            '"use strict"; var bar = {yield: "foo"};'
+        ];
+
+        var fail = function(e) {
+            return e instanceof UglifyJS.JS_Parse_Error &&
+                e.message === "SyntaxError: Unexpected yield identifier inside strict mode";
+        }
+
+        var test = function(input) {
+            return function() {
+                UglifyJS.parse(input);
+            }
+        }
+
+        for (var i = 0; i < tests.length; i++) {
+            assert.throws(test(tests[i]), fail, tests[i]);
+        }
+    });
 });