fix corner cases with parameter scope (#5567)

fixes #5566

lib/compress.js

@@ -2647,16 +2647,17 @@ Compressor.prototype.compress = function(node) {
                         arg = null;
                         return true;
                     }
-                    if (node instanceof AST_ObjectIdentity && (fn_strict || !arg_scope)) {
+                    if (node instanceof AST_ObjectIdentity) {
-                        arg = null;
+                        if (fn_strict || !arg_scope) arg = null;
                         return true;
                     }
-                    if (node instanceof AST_SymbolRef && fn.variables.has(node.name)) {
+                    if (node instanceof AST_SymbolRef) {
-                        var s = node.definition().scope;
+                        var def;
-                        if (s !== scope) while (s = s.parent_scope) {
+                        if (node.in_arg && !is_safe_lexical(node.definition())
-                            if (s === scope) return true;
+                            || (def = fn.variables.get(node.name)) && def !== node.definition()) {
+                            arg = null;
                         }
-                        arg = null;
+                        return true;
                     }
                     if (node instanceof AST_Scope && !is_arrow(node)) {
                         var save_scope = arg_scope;
@@ -5985,7 +5986,7 @@ Compressor.prototype.compress = function(node) {
                     return true;
                 }
                 if (node instanceof AST_SymbolRef) {
-                    if (self.inlined || node.redef) {
+                    if (self.inlined || node.redef || node.in_arg) {
                         result = false;
                         return true;
                     }
@@ -7679,6 +7680,7 @@ Compressor.prototype.compress = function(node) {
                 var def = node.left.definition();
                 if (def.scope.resolve() === self) assignments.add(def.id, node);
             }
+            if (node instanceof AST_SymbolRef && node.in_arg) var_defs[node.definition().id] = 0;
             if (node instanceof AST_Unary && node.expression instanceof AST_SymbolRef) {
                 var def = node.expression.definition();
                 if (def.scope.resolve() === self) assignments.add(def.id, node);
@@ -8172,7 +8174,9 @@ Compressor.prototype.compress = function(node) {
             // collect only vars which don't show up in self's arguments list
             var defns = [];
             if (self instanceof AST_Lambda) self.each_argname(function(argname) {
-                vars.del(argname.name);
+                if (all(argname.definition().references, function(ref) {
+                    return !ref.in_arg;
+                })) vars.del(argname.name);
             });
             vars.each(function(defn, name) {
                 defn = defn.clone();

test/compress/default-values.js

@@ -180,6 +180,26 @@ collapse_arg_sequence: {
     node_version: ">=6"
 }
 
+collapse_in_arg: {
+    options = {
+        collapse_vars: true,
+        keep_fargs: false,
+        unused: true,
+    }
+    input: {
+        (function(a, b = a) {
+            b("PASS");
+        })(console.log);
+    }
+    expect: {
+        (function(a) {
+            a("PASS");
+        })(console.log);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
 collapse_value_1: {
     options = {
         collapse_vars: true,
@@ -2872,3 +2892,127 @@ issue_5536: {
     expect_stdout: "undefined"
     node_version: ">=6"
 }
+
+issue_5566_1: {
+    options = {
+        unused: true,
+    }
+    input: {
+        (function(a, f = function() {
+            return a;
+        }) {
+            var a = "foo";
+            console.log(a, f());
+        })("bar");
+    }
+    expect: {
+        (function(a, f = function() {
+            return a;
+        }) {
+            var a = "foo";
+            console.log(a, f());
+        })("bar");
+    }
+    expect_stdout: "foo bar"
+    node_version: ">=6"
+}
+
+issue_5566_2: {
+    options = {
+        inline: true,
+        reduce_vars: true,
+    }
+    input: {
+        (function(a, f = function() {
+            return a;
+        }) {
+            function a() {}
+            console.log(typeof a, typeof f());
+        })(42);
+    }
+    expect: {
+        (function(a, f = function() {
+            return a;
+        }) {
+            function a() {}
+            console.log(typeof a, typeof f());
+        })(42);
+    }
+    expect_stdout: "function number"
+    node_version: ">=6"
+}
+
+issue_5566_3: {
+    options = {
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        (function(a, f = function() {
+            return a;
+        }) {
+            function a() {}
+            console.log(typeof a, typeof f());
+        })(42);
+    }
+    expect: {
+        (function(a, f = function() {
+            return a;
+        }) {
+            function a() {}
+            console.log(typeof a, typeof f());
+        })(42);
+    }
+    expect_stdout: "function number"
+    node_version: ">=6"
+}
+
+issue_5566_4: {
+    options = {
+        collapse_vars: true,
+        unused: true,
+    }
+    input: {
+        (function(a, b = function() {
+            return a;
+        }) {
+            var a = 0;
+            b()("PASS");
+        })(console.log);
+    }
+    expect: {
+        (function(a, b = function() {
+            return a;
+        }) {
+            var a = 0;
+            b()("PASS");
+        })(console.log);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5566_5: {
+    options = {
+        hoist_vars: true,
+    }
+    input: {
+        (function(a, f = function() {
+            return a;
+        }) {
+            var a = "foo";
+            var b;
+            console.log(a, f());
+        })("bar");
+    }
+    expect: {
+        (function(a, f = function() {
+            return a;
+        }) {
+            var b, a = "foo";
+            console.log(a, f());
+        })("bar");
+    }
+    expect_stdout: "foo bar"
+    node_version: ">=6"
+}

test/reduce.js

@@ -241,23 +241,6 @@ module.exports = function reduce_test(testcase, minify_options, reduce_options)
             CHANGED = true;
             return node.name;
         }
-        else if (node instanceof U.AST_DestructuredArray) {
-            var expr = node.elements[0];
-            if (expr && !(expr instanceof U.AST_Hole)) {
-                node.start._permute++;
-                CHANGED = true;
-                return expr;
-            }
-        }
-        else if (node instanceof U.AST_DestructuredObject) {
-            // first property's value
-            var expr = node.properties[0];
-            if (expr) {
-                node.start._permute++;
-                CHANGED = true;
-                return expr.value;
-            }
-        }
         else if (node instanceof U.AST_Defun) {
             switch (((node.start._permute += step) * steps | 0) % 2) {
               case 0:
@@ -275,6 +258,23 @@ module.exports = function reduce_test(testcase, minify_options, reduce_options)
                 }
             }
         }
+        else if (node instanceof U.AST_DestructuredArray) {
+            var expr = node.elements[0];
+            if (expr && !(expr instanceof U.AST_Hole)) {
+                node.start._permute++;
+                CHANGED = true;
+                return expr;
+            }
+        }
+        else if (node instanceof U.AST_DestructuredObject) {
+            // first property's value
+            var expr = node.properties[0];
+            if (expr) {
+                node.start._permute++;
+                CHANGED = true;
+                return expr.value;
+            }
+        }
         else if (node instanceof U.AST_DWLoop) {
             var expr = [
                 node.condition,
@@ -296,6 +296,16 @@ module.exports = function reduce_test(testcase, minify_options, reduce_options)
                 return to_statement(expr);
             }
         }
+        else if (node instanceof U.AST_ExportDeclaration) {
+            node.start._permute++;
+            CHANGED = true;
+            return node.body;
+        }
+        else if (node instanceof U.AST_ExportDefault) {
+            node.start._permute++;
+            CHANGED = true;
+            return to_statement(node.body);
+        }
         else if (node instanceof U.AST_Finally) {
             // drop finally block
             node.start._permute++;
@@ -351,6 +361,15 @@ module.exports = function reduce_test(testcase, minify_options, reduce_options)
                 return to_statement(expr);
             }
         }
+        else if (node instanceof U.AST_LabeledStatement) {
+            if (node.body instanceof U.AST_Statement
+                && !has_loopcontrol(node.body, node.body, node)) {
+                // replace labelled statement with its non-labelled body
+                node.start._permute = REPLACEMENTS.length;
+                CHANGED = true;
+                return node.body;
+            }
+        }
         else if (node instanceof U.AST_Object) {
             // first property's value
             var expr = node.properties[0];
@@ -441,15 +460,6 @@ module.exports = function reduce_test(testcase, minify_options, reduce_options)
                 return to_statement(node.definitions[0].value);
             }
         }
-        else if (node instanceof U.AST_LabeledStatement) {
-            if (node.body instanceof U.AST_Statement
-                && !has_loopcontrol(node.body, node.body, node)) {
-                // replace labelled statement with its non-labelled body
-                node.start._permute = REPLACEMENTS.length;
-                CHANGED = true;
-                return node.body;
-            }
-        }
 
         if (in_list) {
             // drop switch branches