fix multiple nested function substitutions (#2458)

fixes #2449

test/compress/collapse_vars.js

@@ -3036,6 +3036,7 @@ issue_2437: {
         conditionals: true,
         inline: true,
         join_vars: true,
+        passes: 2,
         reduce_vars: true,
         side_effects: true,
         sequences: true,

test/compress/drop-unused.js

@@ -1113,7 +1113,7 @@ issue_2105_1: {
     options = {
         collapse_vars: true,
         inline: true,
-        passes: 2,
+        passes: 3,
         reduce_vars: true,
         side_effects: true,
         unused: true,
@@ -1153,7 +1153,7 @@ issue_2105_2: {
     options = {
         collapse_vars: true,
         inline: true,
-        passes: 2,
+        passes: 3,
         properties: true,
         pure_getters: "strict",
         reduce_vars: true,

test/compress/functions.js

@@ -513,7 +513,7 @@ issue_2428: {
     options = {
         collapse_vars: true,
         inline: true,
-        passes: 2,
+        passes: 3,
         pure_getters: "strict",
         reduce_vars: true,
         side_effects: true,

test/compress/reduce_vars.js

@@ -3714,6 +3714,7 @@ recursive_inlining_2: {
 
 recursive_inlining_3: {
     options = {
+        passes: 2,
         reduce_vars: true,
         unused: true,
     }
@@ -3989,3 +3990,38 @@ issue_2450_5: {
         "true",
     ]
 }
+
+issue_2449: {
+    options = {
+        passes: 10,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var a = "PASS";
+        function f() {
+            return a;
+        }
+        function g() {
+            return f();
+        }
+        (function() {
+            var a = "FAIL";
+            if (a == a) console.log(g());
+        })();
+    }
+    expect: {
+        var a = "PASS";
+        function g() {
+            return function() {
+                return a;
+            }();
+        }
+        (function() {
+            var a = "FAIL";
+            if (a == a) console.log(g());
+        })();
+    }
+    expect_stdout: "PASS"
+}