fix safari syntax error - declare twice (#1851)

To avoid Safari bug, scope of for loop should enclose parent scope variables.


fixes #1753

lib/minify.js

@@ -57,6 +57,7 @@ function minify(files, options) {
                 keep_fnames: false,
                 properties: false,
                 reserved: [],
+                safari10: false,
                 toplevel: false,
             }, true);
         }

lib/scope.js

@@ -102,6 +102,7 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(options){
     options = defaults(options, {
         cache: null,
         ie8: false,
+        safari10: false,
     });
 
     // pass 1: setup scope chaining and handle definitions
@@ -112,6 +113,7 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(options){
     var in_destructuring = null;
     var in_export = false;
     var in_block = 0;
+    var for_scopes = [];
     var tw = new TreeWalker(function(node, descend){
         if (node.is_block_scope()) {
             var save_scope = scope;
@@ -122,6 +124,11 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(options){
                 scope.uses_eval = save_scope.uses_eval;
                 scope.directives = save_scope.directives;
             }
+            if (options.safari10) {
+                if (node instanceof AST_For || node instanceof AST_ForIn) {
+                    for_scopes.push(scope);
+                }
+            }
             descend();
             scope = save_scope;
             return true;
@@ -303,6 +310,19 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(options){
         }));
     }
 
+    // pass 4: add symbol definitions to loop scopes
+    // Safari/Webkit bug workaround - loop init let variable shadowing argument.
+    // https://github.com/mishoo/UglifyJS2/issues/1753
+    // https://bugs.webkit.org/show_bug.cgi?id=171041
+    if (options.safari10) {
+        for (var i = 0; i < for_scopes.length; i++) {
+            var scope = for_scopes[i];
+            scope.parent_scope.variables.each(function(def) {
+                push_uniq(scope.enclosed, def);
+            });
+        }
+    }
+
     if (options.cache) {
         this.cname = options.cache.cname;
     }

test/compress/harmony.js

@@ -424,3 +424,61 @@ issue_1898: {
         new Foo().bar();
     }
 }
+
+issue_1753: {
+    mangle = { safari10: true };
+    input: {
+        class SomeClass {
+            constructor(props) {
+                let pickedSets = [];
+                for (let i = 0; i < 6; i++) {
+                    pickedSets.push({
+                        mainDrawNumbers: [],
+                        extraDrawNumbers: []
+                    });
+                }
+            }
+        }
+    }
+    expect: {
+        class SomeClass {
+            constructor(r) {
+                let a = [];
+                for (let s = 0; s < 6; s++)
+                    a.push({
+                        mainDrawNumbers: [],
+                        extraDrawNumbers: []
+                    });
+            }
+        }
+    }
+}
+
+issue_1753_disable: {
+    mangle = { safari10: false }
+    input: {
+        class SomeClass {
+            constructor(props) {
+                let pickedSets = [];
+                for (let i = 0; i < 6; i++) {
+                    pickedSets.push({
+                        mainDrawNumbers: [],
+                        extraDrawNumbers: []
+                    });
+                }
+            }
+        }
+    }
+    expect: {
+        class SomeClass {
+            constructor(r) {
+                let a = [];
+                for (let r = 0; r < 6; r++)
+                    a.push({
+                        mainDrawNumbers: [],
+                        extraDrawNumbers: []
+                    });
+            }
+        }
+    }
+}