fix corner cases in inline & unused (#5058)

fixes #5057

lib/compress.js

@@ -3643,7 +3643,7 @@ merge(Compressor.prototype, {
                         stat.init = stat.init.definitions[0].name.convert_symbol(AST_SymbolRef, function(ref, name) {
                             defns.push(make_node(AST_VarDef, name, {
                                 name: name,
-                                value: null
+                                value: null,
                             }));
                             name.definition().references.push(ref);
                         });
@@ -7007,6 +7007,7 @@ merge(Compressor.prototype, {
                 var value = node.value.drop_side_effect_free(compressor);
                 if (!value) return null;
                 log(node.name, "Side effects in default value of unused variable {name}");
+                node.name.__unused = null;
                 node.value = value;
             }
             return node;
@@ -9646,7 +9647,6 @@ merge(Compressor.prototype, {
             fn.each_argname(function(arg) {
                 if (abort) return;
                 if (arg.__unused) return;
-                if (arg instanceof AST_DefaultValue) arg = arg.name;
                 if (!safe_to_inject || var_exists(defined, arg.name)) return abort = true;
                 used[arg.name] = true;
                 if (in_loop) in_loop.push(arg.definition());
@@ -9720,22 +9720,22 @@ merge(Compressor.prototype, {
 
         function append_var(decls, expressions, name, value) {
             var def = name.definition();
-            scope.variables.set(name.name, def);
-            scope.enclosed.push(def);
             if (!scope.var_names()[name.name]) {
                 scope.var_names()[name.name] = true;
                 decls.push(make_node(AST_VarDef, name, {
                     name: name,
-                    value: null
+                    value: null,
                 }));
             }
+            scope.variables.set(name.name, def);
+            scope.enclosed.push(def);
             if (!value) return;
             var sym = make_node(AST_SymbolRef, name, name);
             def.references.push(sym);
             expressions.push(make_node(AST_Assign, self, {
                 operator: "=",
                 left: sym,
-                right: value
+                right: value,
             }));
         }
 

test/compress/default-values.js

@@ -1416,6 +1416,7 @@ issue_4502_1: {
     expect: {
         (function() {
             var a = "PASS";
+            void 0,
             console.log(a),
             a++,
             void 0;
@@ -1439,6 +1440,7 @@ issue_4502_2: {
     expect: {
         (function() {
             var a = "PASS";
+            void 0,
             console.log(a),
             a++,
             void 0;
@@ -1754,3 +1756,78 @@ issue_4994: {
     expect_stdout: "PASS"
     node_version: ">=6"
 }
+
+issue_5057_1: {
+    options = {
+        collapse_vars: true,
+        inline: true,
+        sequences: true,
+        unused: true,
+    }
+    input: {
+        var a = 42;
+        (function() {
+            var b = function(c = (console.log("foo"), b = a)) {
+                a && console.log("bar");
+            }();
+        })();
+    }
+    expect: {
+        var a = 42;
+        console.log("foo"),
+        void (a && console.log("bar"));
+    }
+    expect_stdout: [
+        "foo",
+        "bar",
+    ]
+    node_version: ">=6"
+}
+
+issue_5057_2: {
+    options = {
+        inline: true,
+        unused: true,
+    }
+    input: {
+        (function f(a) {
+            (function(b = console.log("FAIL")) {})(a);
+        })(42);
+        console.log(typeof b);
+    }
+    expect: {
+        (function(a) {
+            [ b = console.log("FAIL") ] = [ a ],
+            void 0;
+            var b;
+        })(42);
+        console.log(typeof b);
+    }
+    expect_stdout: "undefined"
+    node_version: ">=6"
+}
+
+issue_5057_3: {
+    options = {
+        inline: true,
+        unused: true,
+    }
+    input: {
+        (function(a) {
+            (function f(b) {
+                (function(a = console.log("FAIL 1")) {})(b);
+                console.log(a);
+            })("FAIL 2");
+        })("PASS");
+    }
+    expect: {
+        (function(a) {
+            (function(b) {
+                (function(a = console.log("FAIL 1")) {})(b);
+                console.log(a);
+            })("FAIL 2");
+        })("PASS");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}