fix corner case in merge_vars (#5445)

fixes #5444

lib/compress.js

@@ -6033,7 +6033,7 @@ Compressor.prototype.compress = function(node) {
     var NO_MERGE = makePredicate("arguments await yield");
     AST_Scope.DEFMETHOD("merge_variables", function(compressor) {
         if (!compressor.option("merge_vars")) return;
-        var in_try, root, segment = {}, self = this;
+        var in_arg = [], in_try, root, segment = {}, self = this;
         var first = [], last = [], index = 0;
         var declarations = new Dictionary();
         var references = Object.create(null);
@@ -6183,45 +6183,29 @@ Compressor.prototype.compress = function(node) {
                 return true;
             }
             if (node instanceof AST_Scope) {
+                var parent = tw.parent();
+                var in_iife = parent && parent.TYPE == "Call" && parent.expression === node;
+                if (!in_iife) {
                     push();
                     segment.block = node;
+                }
                 if (node === self) root = segment;
                 if (node instanceof AST_Lambda) {
                     if (node.name) references[node.name.definition().id] = false;
-                    var parent = tw.parent();
-                    var in_iife = parent && parent.TYPE == "Call" && parent.expression === node;
                     var marker = node.uses_arguments && !tw.has_directive("use strict") ? function(node) {
                         if (node instanceof AST_SymbolFunarg) references[node.definition().id] = false;
                     } : function(node) {
                         if (node instanceof AST_SymbolFunarg) mark(node);
                     };
-                    var scanner = new TreeWalker(function(ref) {
-                        if (ref instanceof AST_SymbolDeclaration) references[ref.definition().id] = false;
-                        if (!(ref instanceof AST_SymbolRef)) return;
-                        var def = ref.definition();
-                        var ldef = node.variables.get(ref.name);
-                        if (ldef && (ldef === def
-                            || def.undeclared
-                            || node.parent_scope.find_variable(ref.name) === def)) {
-                            references[def.id] = false;
-                            references[ldef.id] = false;
-                        } else if (in_iife) {
-                            var save = segment;
-                            pop();
-                            mark(ref, true);
-                            segment = save;
-                        } else {
-                            mark(ref, true);
-                        }
-                        return true;
-                    });
+                    in_arg.push(node);
                     node.argnames.forEach(function(argname) {
-                        argname.mark_symbol(marker, scanner);
+                        argname.mark_symbol(marker, tw);
                     });
-                    if (node.rest) node.rest.mark_symbol(marker, scanner);
+                    if (node.rest) node.rest.mark_symbol(marker, tw);
+                    in_arg.pop();
                 }
                 walk_lambda(node, tw);
-                pop();
+                if (!in_iife) pop();
                 return true;
             }
             if (node instanceof AST_Sub) {
@@ -6433,7 +6417,16 @@ Compressor.prototype.compress = function(node) {
         }
 
         function mark(sym, read) {
-            var def = sym.definition(), ldef, seg = segment;
+            var def = sym.definition(), ldef;
+            if (read && !all(in_arg, function(fn) {
+                ldef = fn.variables.get(sym.name);
+                if (!ldef) return true;
+                if (!is_funarg(ldef)) return true;
+                return ldef !== def
+                    && !def.undeclared
+                    && fn.parent_scope.find_variable(sym.name) !== def;
+            })) return references[def.id] = references[ldef.id] = false;
+            var seg = segment;
             if (in_try) {
                 push();
                 seg = segment;

test/compress.js

@@ -69,9 +69,7 @@ function make_code(ast, options) {
 function parse_test(file) {
     var script = fs.readFileSync(file, "utf8");
     try {
-        var ast = U.parse(script, {
-            filename: file
-        });
+        var ast = U.parse(script, { filename: file });
     } catch (e) {
         console.error("Caught error while parsing tests in " + file);
         console.error(e);
@@ -98,7 +96,7 @@ function parse_test(file) {
             file: file,
             line: node.start.line,
             col: node.start.col,
-            code: make_code(node, { beautify: false })
+            code: make_code(node, { beautify: false }),
         }));
     }
 
@@ -142,7 +140,7 @@ function parse_test(file) {
                 ].indexOf(label.name) >= 0, tmpl("Unsupported label {name} [{line},{col}]", {
                     name: label.name,
                     line: label.start.line,
-                    col: label.start.col
+                    col: label.start.col,
                 }));
                 var stat = node.body;
                 if (label.name == "expect_exact" || label.name == "node_version") {
@@ -155,12 +153,12 @@ function parse_test(file) {
                         var ctor = global[body.expression.name];
                         assert.ok(ctor === Error || ctor.prototype instanceof Error, tmpl("Unsupported expect_stdout format [{line},{col}]", {
                             line: label.start.line,
-                            col: label.start.col
+                            col: label.start.col,
                         }));
                         test[label.name] = ctor.apply(null, body.args.map(function(node) {
                             assert.ok(node instanceof U.AST_Constant, tmpl("Unsupported expect_stdout format [{line},{col}]", {
                                 line: label.start.line,
-                                col: label.start.col
+                                col: label.start.col,
                             }));
                             return node.value;
                         }));

test/compress/arrows.js

@@ -726,8 +726,8 @@ issue_4401: {
     expect: {
         (function() {
             var a = (b => b(a))(console.log || a);
-            var c = console.log;
-            c && c(typeof b);
+            var a = console.log;
+            a && a(typeof b);
         })();
     }
     expect_stdout: [

test/compress/const.js

@@ -184,12 +184,12 @@ merge_vars_2: {
     expect: {
         var a = 0;
         1 && --a,
-        b = function f() {
+        a = function f() {
             const c = a && f;
             c.var += 0;
         }(),
-        void console.log(b);
-        var b;
+        void console.log(a);
+        var a;
     }
     expect_stdout: "undefined"
 }

test/compress/default-values.js

@@ -2239,3 +2239,77 @@ issue_5407: {
     ]
     node_version: ">=6"
 }
+
+issue_5444_1: {
+    options = {
+        merge_vars: true,
+        toplevel: true,
+    }
+    input: {
+        var a = 42;
+        var b = function({} = setImmediate(function() {
+            console.log(a++);
+        })) {
+            return this;
+        }();
+        console.log(typeof b);
+    }
+    expect: {
+        var a = 42;
+        var b = function({} = setImmediate(function() {
+            console.log(a++);
+        })) {
+            return this;
+        }();
+        console.log(typeof b);
+    }
+    expect_stdout: [
+        "object",
+        "42",
+    ]
+    node_version: ">=6"
+}
+
+issue_5444_2: {
+    options = {
+        merge_vars: true,
+    }
+    input: {
+        function f(a, b = a++) {
+            return b;
+        }
+        console.log(f("FAIL") || "PASS");
+    }
+    expect: {
+        function f(a, b = a++) {
+            return b;
+        }
+        console.log(f("FAIL") || "PASS");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5444_3: {
+    options = {
+        merge_vars: true,
+    }
+    input: {
+        function f(a, b = function(c = a *= this) {
+            return c;
+        }()) {
+            return b;
+        }
+        console.log(f("FAIL") || "PASS");
+    }
+    expect: {
+        function f(a, b = function(c = a *= this) {
+            return c;
+        }()) {
+            return b;
+        }
+        console.log(f("FAIL") || "PASS");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}

test/compress/destructured.js

@@ -1815,8 +1815,8 @@ issue_4288: {
                 console.log(typeof b);
             }()]: a,
         }) {
-            var b = a;
-            b++;
+            var a = a;
+            a++;
         }
         f(0);
     }

test/compress/let.js

@@ -237,12 +237,12 @@ merge_vars_2: {
         "use strict";
         var a = 0;
         1 && --a,
-        b = function f() {
+        a = function f() {
             let c = a && f;
             c.var += 0;
         }(),
-        void console.log(b);
-        var b;
+        void console.log(a);
+        var a;
     }
     expect_stdout: "undefined"
     node_version: ">=4"