fix corner case in `reduce_vars` (#5051)

fixes #5050

2 files changed, 42 insertions, 19 deletions

diff --git a/lib/compress.js b/lib/compress.js
index 4aefb8db..e0b7597b 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -526,7 +526,7 @@ merge(Compressor.prototype, {
             if (fn.parent_scope.resolve().may_call_this === return_true) return;
             if (marker) {
                 var visited = member(fn, tw.fn_visited);
-                if (marker === tw.safe_ids) return !visited && fn;
+                if (marker === tw.safe_ids) return !visited && walk_fn_def(tw, fn);
                 if (visited) {
                     fn.enclosed.forEach(function(d) {
                         if (fn.variables.get(d.name) === d) return;
@@ -539,7 +539,7 @@ merge(Compressor.prototype, {
                 }
             } else if (!tw.in_loop && !(tw.fn_scanning && tw.fn_scanning !== def.scope.resolve())) {
                 fn.safe_ids = tw.safe_ids;
-                return fn;
+                return walk_fn_def(tw, fn);
             }
             fn.safe_ids = false;
         }
@@ -1013,21 +1013,18 @@ merge(Compressor.prototype, {
                 }
             }
             exp.walk(tw);
-            var fixed = exp instanceof AST_SymbolRef && exp.fixed_value();
             var optional = node.optional;
-            var fn;
-            if (fixed instanceof AST_Lambda) {
-                fn = mark_fn_def(tw, exp.definition(), fixed);
-                optional = false;
-            } else {
-                tw.find_parent(AST_Scope).may_call_this();
-            }
             if (optional) push(tw);
             node.args.forEach(function(arg) {
                 arg.walk(tw);
             });
             if (optional) pop(tw);
-            if (fn) walk_fn_def(tw, fn);
+            var fixed = exp instanceof AST_SymbolRef && exp.fixed_value();
+            if (fixed instanceof AST_Lambda) {
+                mark_fn_def(tw, exp.definition(), fixed);
+            } else {
+                tw.find_parent(AST_Scope).may_call_this();
+            }
             return true;
         });
         def(AST_Class, function(tw, descend, compressor) {
@@ -1283,8 +1280,7 @@ merge(Compressor.prototype, {
             var parent;
             if (value instanceof AST_Lambda
                 && !((parent = tw.parent()) instanceof AST_Call && parent.expression === this)) {
-                var fn = mark_fn_def(tw, d, value);
-                if (fn) walk_fn_def(tw, fn);
+                mark_fn_def(tw, d, value);
             }
         });
         def(AST_Template, function(tw, descend) {
@@ -1299,17 +1295,15 @@ merge(Compressor.prototype, {
                 return true;
             }
             tag.walk(tw);
+            node.expressions.forEach(function(exp) {
+                exp.walk(tw);
+            });
             var fixed = tag instanceof AST_SymbolRef && tag.fixed_value();
-            var fn;
             if (fixed instanceof AST_Lambda) {
-                fn = mark_fn_def(tw, tag.definition(), fixed);
+                mark_fn_def(tw, tag.definition(), fixed);
             } else {
                 tw.find_parent(AST_Scope).may_call_this();
             }
-            node.expressions.forEach(function(exp) {
-                exp.walk(tw);
-            });
-            if (fn) walk_fn_def(tw, fn);
             return true;
         });
         def(AST_Toplevel, function(tw, descend, compressor) {
diff --git a/test/compress/reduce_vars.js b/test/compress/reduce_vars.js
index 735688ea..4af4945f 100644
--- a/test/compress/reduce_vars.js
+++ b/test/compress/reduce_vars.js
@@ -7696,3 +7696,32 @@ issue_5048: {
     }
     expect_stdout: "undefined"
 }
+
+issue_5050: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        toplevel: true,
+    }
+    input: {
+        function f() {
+            console.log(a);
+        }
+        this;
+        var a = 1;
+        f(console.log(2), f(), a = 3);
+    }
+    expect: {
+        function f() {
+            console.log(a);
+        }
+        this;
+        var a = 1;
+        f(console.log(2), f(), a = 3);
+    }
+    expect_stdout: [
+        "2",
+        "1",
+        "3",
+    ]
+}