fix export default of anonymous generators and async functions (#2607)

fixes #2606

lib/parse.js

@@ -982,7 +982,7 @@ function parse($TEXT, options) {
         }
     };
 
-    var statement = embed_tokens(function() {
+    var statement = embed_tokens(function(is_export_default) {
         handle_regexp();
         switch (S.token.type) {
           case "string":
@@ -1011,7 +1011,7 @@ function parse($TEXT, options) {
             if (S.token.value == "async" && is_token(peek(), "keyword", "function")) {
                 next();
                 next();
-                return function_(AST_Defun, false, true);
+                return function_(AST_Defun, false, true, is_export_default);
             }
             if (S.token.value == "import" && !is_token(peek(), "punc", "(")) {
                 next();
@@ -1085,7 +1085,7 @@ function parse($TEXT, options) {
 
               case "function":
                 next();
-                return function_(AST_Defun);
+                return function_(AST_Defun, false, false, is_export_default);
 
               case "if":
                 next();
@@ -1308,9 +1308,9 @@ function parse($TEXT, options) {
         });
     };
 
-    var function_ = function(ctor, is_generator_property, is_async) {
+    var function_ = function(ctor, is_generator_property, is_async, is_export_default) {
         if (is_generator_property && is_async) croak("generators cannot be async");
-        var start = S.token
+        var start = S.token;
 
         var in_statement = ctor === AST_Defun;
         var is_generator = is("operator", "*");
@@ -1319,8 +1319,13 @@ function parse($TEXT, options) {
         }
 
         var name = is("name") ? as_symbol(in_statement ? AST_SymbolDefun : AST_SymbolLambda) : null;
-        if (in_statement && !name)
+        if (in_statement && !name) {
+            if (is_export_default) {
+                ctor = AST_Function;
+            } else {
                 unexpected();
+            }
+        }
 
         if (name && ctor !== AST_Accessor && !(name instanceof AST_SymbolDeclaration))
             unexpected(prev());
@@ -2528,9 +2533,9 @@ function parse($TEXT, options) {
                 && is_token(peek(), "punc")) {
             exported_value = expression(false);
             semicolon();
-        } else if ((node = statement()) instanceof AST_Definitions && is_default) {
+        } else if ((node = statement(is_default)) instanceof AST_Definitions && is_default) {
             unexpected(node.start);
-        } else if (node instanceof AST_Definitions || node instanceof AST_Defun || node instanceof AST_DefClass) {
+        } else if (node instanceof AST_Definitions || node instanceof AST_Lambda || node instanceof AST_DefClass) {
             exported_definition = node;
         } else if (node instanceof AST_SimpleStatement) {
             exported_value = node.body;

test/compress/export.js

@@ -262,3 +262,185 @@ trailing_comma: {
     }
     expect_exact: "export const a = 1;"
 }
+
+export_default_anonymous_function: {
+    options = {
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    mangle = {
+        toplevel: true,
+    }
+    input: {
+        export default function () {
+            foo();
+        }
+    }
+    expect_exact: "export default function(){foo()};"
+}
+
+export_default_arrow: {
+    options = {
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    mangle = {
+        toplevel: true,
+    }
+    input: {
+        export default () => foo();
+    }
+    expect_exact: "export default()=>foo();"
+}
+
+export_default_anonymous_generator: {
+    options = {
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    mangle = {
+        toplevel: true,
+    }
+    input: {
+        export default function * () {
+            yield foo();
+        }
+    }
+    expect_exact: "export default function*(){yield foo()};"
+}
+
+export_default_anonymous_async_function: {
+    options = {
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    mangle = {
+        toplevel: true,
+    }
+    input: {
+        export default async function() {
+            return await foo();
+        }
+    }
+    expect_exact: "export default async function(){return await foo()};"
+}
+
+export_default_async_arrow_function: {
+    options = {
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    mangle = {
+        toplevel: true,
+    }
+    input: {
+        export default async () => await foo();
+    }
+    expect_exact: "export default async()=>await foo();"
+}
+
+export_default_named_generator: {
+    options = {
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    mangle = {
+        toplevel: true,
+    }
+    input: {
+        export default function * gen() {
+            yield foo();
+        }
+    }
+    expect_exact: "export default function*gen(){yield foo()};"
+}
+
+export_default_named_async_function: {
+    options = {
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    mangle = {
+        toplevel: true,
+    }
+    input: {
+        export default async function bar() {
+            return await foo();
+        }
+    }
+    expect_exact: "export default async function bar(){return await foo()};"
+}
+
+export_default_anonymous_class: {
+    options = {
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    mangle = {
+        toplevel: true,
+    }
+    input: {
+        export default class {
+            constructor() {
+                foo();
+            }
+        };
+    }
+    expect_exact: "export default class{constructor(){foo()}};"
+}
+
+export_default_anonymous_function_not_call: {
+    options = {
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    mangle = {
+        toplevel: true,
+    }
+    input: {
+        export default function(){}(foo);
+    }
+    // FIXME: should be `export default function(){};foo;`
+    expect_exact: "export default function(){}(foo);"
+}
+
+export_default_anonymous_generator_not_call: {
+    options = {
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    mangle = {
+        toplevel: true,
+    }
+    input: {
+        export default function*(){}(foo);
+    }
+    // agrees with `acorn` and `babylon 7`
+    expect_exact: "export default function*(){};foo;"
+}
+
+export_default_anonymous_async_function_not_call: {
+    options = {
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    mangle = {
+        toplevel: true,
+    }
+    input: {
+        export default async function(){}(foo);
+    }
+    // agrees with `acorn` and `babylon 7`
+    expect_exact: "export default async function(){};foo;"
+}