Mangling externally imported names by using aliasing

lib/ast.js

@@ -707,6 +707,12 @@ var AST_NameImport = DEFNODE("NameImport", "foreign_name name", {
     $propdoc: {
         foreign_name: "[AST_SymbolImportForeign] The name being imported (as specified in the module)",
         name: "[AST_SymbolImport] The name as it becomes available to this module."
+    },
+    _walk: function (visitor) {
+        return visitor._visit(this, function() {
+            this.foreign_name._walk(visitor);
+            this.name._walk(visitor);
+        });
     }
 })
 
@@ -722,6 +728,11 @@ var AST_Import = DEFNODE("Import", "imported_name imported_names module_name", {
             if (this.imported_name) {
                 this.imported_name._walk(visitor);
             }
+            if (this.imported_names) {
+                this.imported_names.forEach(function (name_import) {
+                    name_import._walk(visitor);
+                });
+            }
             this.module_name._walk(visitor);
         });
     }

lib/output.js

@@ -1070,8 +1070,12 @@ function OutputStream(options) {
     });
 
     DEFPRINT(AST_NameImport, function(self, output) {
-        if (self.foreign_name) {
+        var definition = self.name.definition();
-            self.foreign_name.print(output);
+        var names_are_different =
+            (definition && definition.mangled_name || self.name.name) !==
+            self.foreign_name.name;
+        if (names_are_different) {
+            output.print(self.foreign_name.name);
             output.space();
             output.print("as");
             output.space();

lib/parse.js

@@ -1667,6 +1667,14 @@ function parse($TEXT, options) {
         }
         name = as_symbol(AST_SymbolImport);
 
+        if (foreign_name === undefined) {
+            foreign_name = new AST_SymbolImportForeign({
+                name: name.name,
+                start: name.start,
+                end: name.end,
+            });
+        }
+
         return new AST_NameImport({
             start: start,
             foreign_name: foreign_name,

lib/scope.js

@@ -171,6 +171,9 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(options){
         else if (node instanceof AST_SymbolClass) {
             defun.def_variable(node);
         }
+        else if (node instanceof AST_SymbolImport) {
+            scope.def_variable(node);
+        }
         else if (node instanceof AST_SymbolDefClass) {
             // This deals with the name of the class being available
             // inside the class.
@@ -302,6 +305,12 @@ AST_Scope.DEFMETHOD("def_variable", function(symbol){
         this.variables.set(symbol.name, def);
         def.object_destructuring_arg = symbol.object_destructuring_arg;
         def.global = !this.parent_scope;
+        if (symbol instanceof AST_SymbolImport) {
+            // Imports are not global
+            def.global = false;
+            // TODO The real fix comes with block scoping being first class in uglifyJS,
+            // enabling import definitions to behave like module-level let declarations
+        }
     } else {
         def = this.variables.get(symbol.name);
         def.orig.push(symbol);

test/compress/harmony.js

@@ -320,11 +320,21 @@ import_statement_mangling: {
     mangle = { };
     input: {
         import Foo from "foo";
+        import Bar, {Food} from "lel";
+        import {What as Whatever} from "lel";
         Foo();
+        Bar();
+        Food();
+        Whatever();
     }
     expect: {
         import a from "foo";
+        import b, {Food as c} from "lel";
+        import {What as d} from "lel";
         a();
+        b();
+        c();
+        d();
     }
 }