fix corner case in inline (#5410)

fixes #5409

lib/compress.js

@@ -13160,6 +13160,19 @@ Compressor.prototype.compress = function(node) {
         return found;
     }
 
+    function insert_assign(def, assign) {
+        var visited = [];
+        def.references.forEach(function(ref) {
+            var fixed = ref.fixed;
+            if (!fixed || !push_uniq(visited, fixed)) return;
+            if (fixed.assigns) {
+                fixed.assigns.unshift(assign);
+            } else {
+                fixed.assigns = [ assign ];
+            }
+        });
+    }
+
     function init_ref(compressor, name) {
         var sym = make_node(AST_SymbolRef, name, name);
         var assign = make_node(AST_Assign, name, {
@@ -13173,16 +13186,7 @@ Compressor.prototype.compress = function(node) {
                 return assign.right;
             };
             sym.fixed.assigns = [ assign ];
-            var visited = [];
-            def.references.forEach(function(ref) {
-                var fixed = ref.fixed;
-                if (!fixed || !push_uniq(visited, fixed)) return;
-                if (fixed.assigns) {
-                    fixed.assigns.unshift(assign);
-                } else {
-                    fixed.assigns = [ assign ];
-                }
-            });
+            insert_assign(def, assign);
         }
         def.assignments++;
         def.references.push(sym);
@@ -13391,12 +13395,12 @@ Compressor.prototype.compress = function(node) {
                         if (value) body.push(make_node(AST_SimpleStatement, call, { body: value }));
                         return;
                     }
-                    body.push(make_node(AST_Var, call, {
-                        definitions: [ make_node(AST_VarDef, call, {
-                            name: argname.convert_symbol(AST_SymbolVar, process),
-                            value: value || make_node(AST_Undefined, call).transform(compressor),
-                        }) ],
-                    }));
+                    var defn = make_node(AST_VarDef, call, {
+                        name: argname.convert_symbol(AST_SymbolVar, process),
+                        value: value || make_node(AST_Undefined, call).transform(compressor),
+                    });
+                    if (argname instanceof AST_SymbolFunarg) insert_assign(argname.definition(), defn);
+                    body.push(make_node(AST_Var, call, { definitions: [ defn ] }));
                 });
                 if (values.length) body.push(make_node(AST_SimpleStatement, call, {
                     body: make_sequence(call, values),

test/compress/functions.js

@@ -8370,3 +8370,31 @@ issue_5401: {
     }
     expect_stdout: "PASS"
 }
+
+issue_5409: {
+    options = {
+        inline: true,
+        merge_vars: true,
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        (function(a) {
+            (a = console) || FAIL(a);
+            (function(b) {
+                console.log(b && b);
+                while (!console);
+            })();
+        })();
+    }
+    expect: {
+        (function(a) {
+            (a = console) || FAIL(a);
+            a = void 0;
+            console.log(a && a);
+            while (!console);
+            return;
+        })();
+    }
+    expect_stdout: "undefined"
+}

test/compress/keep_fargs.js

@@ -1258,8 +1258,7 @@ issues_3267_1: {
     }
     expect: {
         !function() {
-            var i = Object();
-            if (i)
+            if (Object())
                 return console.log("PASS");
             throw "FAIL";
         }();

test/compress/reduce_vars.js

@@ -6689,8 +6689,7 @@ issues_3267_1: {
     }
     expect: {
         !function(x) {
-            var i = Object();
-            if (i)
+            if (Object())
                 return console.log("PASS");
             throw "FAIL";
         }();