enhance `reduce_vars` (#5038)

2 files changed, 40 insertions, 44 deletions

diff --git a/lib/compress.js b/lib/compress.js
index 0f9f0795..1be74033 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -477,14 +477,6 @@ merge(Compressor.prototype, {
                 && !compressor.exposed(def)
                 && !(def.init instanceof AST_LambdaExpression && def.init !== def.scope)
                 && def.init;
-            if (def.fixed instanceof AST_LambdaDefinition && !all(def.references, function(ref) {
-                var scope = ref.scope.resolve();
-                do {
-                    if (def.scope === scope) return true;
-                } while (scope instanceof AST_LambdaExpression && (scope = scope.parent_scope.resolve()));
-            })) {
-                tw.defun_ids[def.id] = false;
-            }
             def.reassigned = 0;
             def.recursive_refs = 0;
             def.references = [];
@@ -526,23 +518,25 @@ merge(Compressor.prototype, {
                 var marker = tw.defun_ids[def.id];
                 if (!marker) return;
                 var visited = tw.defun_visited[def.id];
-                if (marker === tw.safe_ids) {
-                    if (!visited) return def.fixed;
-                } else if (visited) {
+                if (marker === tw.safe_ids) return !visited && def.fixed;
+                if (visited) {
                     def.init.enclosed.forEach(function(d) {
                         if (def.init.variables.get(d.name) === d) return;
                         if (!safe_to_read(tw, d)) d.fixed = false;
                     });
-                } else {
-                    tw.defun_ids[def.id] = false;
-                }
-            } else {
-                if (!tw.in_loop) {
-                    tw.defun_ids[def.id] = tw.safe_ids;
-                    return def.fixed;
+                    return;
                 }
-                tw.defun_ids[def.id] = false;
+            } else if (!tw.in_loop) {
+                var scope = def.scope;
+                var s = tw.find_parent(AST_Scope);
+                do {
+                    if (s === scope) {
+                        tw.defun_ids[def.id] = tw.safe_ids;
+                        return def.fixed;
+                    }
+                } while (s instanceof AST_LambdaExpression && (s = s.parent_scope.resolve()));
             }
+            tw.defun_ids[def.id] = false;
         }
 
         function walk_defuns(tw, scope) {
@@ -967,11 +961,11 @@ merge(Compressor.prototype, {
             });
         });
         def(AST_Call, function(tw, descend) {
-            tw.find_parent(AST_Scope).may_call_this();
-            var exp = this.expression;
+            var node = this;
+            var exp = node.expression;
             if (exp instanceof AST_LambdaExpression) {
-                var iife = is_iife_single(this);
-                this.args.forEach(function(arg) {
+                var iife = is_iife_single(node);
+                node.args.forEach(function(arg) {
                     arg.walk(tw);
                     if (arg instanceof AST_Spread) iife = false;
                 });
@@ -980,28 +974,28 @@ merge(Compressor.prototype, {
                 if (iife) delete exp.reduce_vars;
                 return true;
             }
-            if (exp instanceof AST_SymbolRef) {
-                var def = exp.definition();
-                if (this.TYPE == "Call" && tw.in_boolean_context()) def.bool_fn++;
-                if (def.fixed instanceof AST_LambdaDefinition) {
-                    var defun = mark_defun(tw, def);
-                    if (defun) {
-                        descend();
-                        defun.walk(tw);
-                        return true;
-                    }
+            var def = exp instanceof AST_SymbolRef && exp.definition();
+            if (node.TYPE == "Call" && tw.in_boolean_context()) {
+                if (def) {
+                    def.bool_fn++;
+                } else if (exp instanceof AST_Assign && exp.operator == "=" && exp.left instanceof AST_SymbolRef) {
+                    exp.left.definition().bool_fn++;
                 }
-            } else if (this.TYPE == "Call"
-                && exp instanceof AST_Assign
-                && exp.operator == "="
-                && exp.left instanceof AST_SymbolRef
-                && tw.in_boolean_context()) {
-                exp.left.definition().bool_fn++;
             }
-            if (!this.optional) return;
+            if (def && def.fixed instanceof AST_LambdaDefinition) {
+                var defun = mark_defun(tw, def);
+                if (defun) {
+                    descend();
+                    defun.walk(tw);
+                    return true;
+                }
+            } else {
+                tw.find_parent(AST_Scope).may_call_this();
+            }
+            if (!node.optional) return;
             exp.walk(tw);
             push(tw);
-            this.args.forEach(function(arg) {
+            node.args.forEach(function(arg) {
                 arg.walk(tw);
             });
             pop(tw);
@@ -10911,7 +10905,10 @@ merge(Compressor.prototype, {
                         single_use = false;
                     }
                     if (single_use) fixed.parent_scope = self.scope;
-                } else if (!fixed || !fixed.is_constant_expression() || fixed.drop_side_effect_free(compressor)) {
+                } else if (!fixed
+                    || def.recursive_refs > 0
+                    || !fixed.is_constant_expression()
+                    || fixed.drop_side_effect_free(compressor)) {
                     single_use = false;
                 }
             }
diff --git a/test/compress/merge_vars.js b/test/compress/merge_vars.js
index e29298ed..6c079d90 100644
--- a/test/compress/merge_vars.js
+++ b/test/compress/merge_vars.js
@@ -2735,8 +2735,7 @@ issue_4135: {
         0;
         a++;
         if (!a)
-            c = (a++, c = 0, void (c && c.p));
-        var c;
+            var c = void a++;
         console.log(a, -1, c);
     }
     expect_stdout: "1 -1 undefined"