fix export default

- prohibit definition statements
- parse `AST_Defun` properly
- drop only unused class and function names

lib/compress.js

@@ -2021,7 +2021,7 @@ merge(Compressor.prototype, {
         var tw = new TreeWalker(function(node, descend){
             if (node !== self) {
                 if (node instanceof AST_Defun || node instanceof AST_DefClass) {
-                    if ((!drop_funcs || tw.parent() instanceof AST_Export) && scope === self) {
+                    if (!drop_funcs && scope === self) {
                         var node_def = node.name.definition();
                         if (node_def.global && !(node_def.id in in_use_ids)) {
                             in_use_ids[node_def.id] = true;
@@ -2157,9 +2157,11 @@ merge(Compressor.prototype, {
         // pass 3: we should drop declarations not in_use
         var tt = new TreeTransformer(
             function before(node, descend, in_list) {
-                if (node instanceof AST_Function
+                var parent = tt.parent();
-                    && node.name
+                if (!compressor.option("keep_fnames")
-                    && !compressor.option("keep_fnames")) {
+                    && ((node instanceof AST_Function || node instanceof AST_ClassExpression) && node.name
+                        || (node instanceof AST_Defun || node instanceof AST_DefClass)
+                            && parent instanceof AST_Export && parent.is_default)) {
                     var def = node.name.definition();
                     // any declarations with same name will overshadow
                     // name of this anonymous function and can therefore
@@ -2194,7 +2196,7 @@ merge(Compressor.prototype, {
                         }
                     }
                 }
-                if ((node instanceof AST_Defun || node instanceof AST_DefClass) && node !== self) {
+                if ((node instanceof AST_Defun || node instanceof AST_DefClass) && !(parent instanceof AST_Export) && node !== self) {
                     var keep = (node.name.definition().id in in_use_ids) || !drop_funcs && node.name.definition().global;
                     if (!keep) {
                         compressor[node.name.unreferenced() ? "warn" : "info"]("Dropping unused function {name} [{file}:{line},{col}]", template(node.name));
@@ -2202,7 +2204,7 @@ merge(Compressor.prototype, {
                     }
                     return node;
                 }
-                if (node instanceof AST_Definitions && !(tt.parent() instanceof AST_ForIn && tt.parent().init === node)) {
+                if (node instanceof AST_Definitions && !(parent instanceof AST_ForIn && parent.init === node)) {
                     // place uninitialized names at the start
                     var body = [], head = [], tail = [];
                     // for unused names whose initialization has
@@ -2298,7 +2300,7 @@ merge(Compressor.prototype, {
                     if (!(def.id in in_use_ids)
                         && (drop_vars || !def.global)
                         && self.variables.get(def.name) === def) {
-                        return maintain_this_binding(tt.parent(), node, node.right.transform(tt));
+                        return maintain_this_binding(parent, node, node.right.transform(tt));
                     }
                 }
                 // certain combination of unused name + side effect leads to:

lib/parse.js

@@ -2417,14 +2417,26 @@ function parse($TEXT, options) {
             }
         }
 
-        var is_definition = is("keyword", "var")
+        var is_definition = is("keyword", "var") || is("keyword", "let") || is("keyword", "const");
-            || is("keyword", "let")
-            || is("keyword", "const")
-            || is("keyword", "function") && !is_default;
         if (is_definition) {
+            if (is_default) unexpected();
             exported_definition = statement();
+        } else if (is("keyword", "class")) {
+            var cls = expr_atom(false);
+            if (cls.name) {
+                cls.name = new AST_SymbolDefClass(cls.name);
+                exported_definition = new AST_DefClass(cls);
+            } else {
+                exported_value = cls;
+            }
         } else if (is("keyword", "function")) {
-            exported_value = expr_atom(false);
+            var func = expr_atom(false);
+            if (func.name) {
+                func.name = new AST_SymbolDefun(func.name);
+                exported_definition = new AST_Defun(func);
+            } else {
+                exported_value = func;
+            }
         } else {
             exported_value = expression(false);
             semicolon();

lib/scope.js

@@ -230,7 +230,8 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(options){
         }
 
         function mark_export(def, level) {
-            def.export = tw.parent(level) instanceof AST_Export;
+            var node = tw.parent(level);
+            def.export = node instanceof AST_Export && !node.is_default;
         }
     });
     self.walk(tw);

test/compress/issue-2001.js

@@ -1,6 +1,7 @@
 export_func_1: {
     options = {
         hoist_funs: true,
+        toplevel: true,
         unused: true,
     }
     input: {
@@ -13,6 +14,7 @@ export_func_2: {
     options = {
         hoist_funs: true,
         side_effects: false,
+        toplevel: true,
         unused: true,
     }
     input: {
@@ -25,6 +27,7 @@ export_func_3: {
     options = {
         hoist_funs: true,
         side_effects: true,
+        toplevel: true,
         unused: true,
     }
     input: {
@@ -36,6 +39,7 @@ export_func_3: {
 export_default_func_1: {
     options = {
         hoist_funs: true,
+        toplevel: true,
         unused: true,
     }
     input: {
@@ -48,6 +52,7 @@ export_default_func_2: {
     options = {
         hoist_funs: true,
         side_effects: false,
+        toplevel: true,
         unused: true,
     }
     input: {
@@ -60,6 +65,7 @@ export_default_func_3: {
     options = {
         hoist_funs: true,
         side_effects: true,
+        toplevel: true,
         unused: true,
     }
     input: {
@@ -68,6 +74,82 @@ export_default_func_3: {
     expect_exact: "export default function(){};"
 }
 
+export_class_1: {
+    options = {
+        hoist_funs: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        export class C {};
+    }
+    expect_exact: "export class C{};"
+}
+
+export_class_2: {
+    options = {
+        hoist_funs: true,
+        side_effects: false,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        export class C {}(1);
+    }
+    expect_exact: "export class C{};1;"
+}
+
+export_class_3: {
+    options = {
+        hoist_funs: true,
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        export class C {}(1);
+    }
+    expect_exact: "export class C{};"
+}
+
+export_default_class_1: {
+    options = {
+        hoist_funs: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        export default class C {};
+    }
+    expect_exact: "export default class{};"
+}
+
+export_default_class_2: {
+    options = {
+        hoist_funs: true,
+        side_effects: false,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        export default class C {}(1);
+    }
+    expect_exact: "export default class{};1;"
+}
+
+export_default_class_3: {
+    options = {
+        hoist_funs: true,
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        export default class C {}(1);
+    }
+    expect_exact: "export default class{};"
+}
+
 export_mangle_1: {
     mangle = {
         toplevel: true,
@@ -89,7 +171,7 @@ export_mangle_2: {
             return one - two;
         };
     }
-    expect_exact: "export default function n(r,t){return r-t};"
+    expect_exact: "export default function n(n,r){return n-r};"
 }
 
 export_mangle_3: {
@@ -125,7 +207,7 @@ export_mangle_4: {
             }
         };
     }
-    expect_exact: "export default class C{go(n,r){return n-r+n}};"
+    expect_exact: "export default class n{go(n,r){return n-r+n}};"
 }
 
 export_mangle_5: {
@@ -181,6 +263,19 @@ export_toplevel_2: {
     }
     expect: {
         export class B {};
-        export default class C {};
+        export default class {};
     }
 }
+
+export_default_func_ref: {
+    options = {
+        hoist_funs: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        export default function f(){};
+        f();
+    }
+    expect_exact: "export default function f(){};f();"
+}