handle AST_Arrow IIFEs in collapse_vars

lib/compress.js

@@ -850,8 +850,8 @@ merge(Compressor.prototype, {
             }
 
             function has_overlapping_symbol(fn, arg) {
-                var found = false;
-                var tw = new TreeWalker(function(node) {
+                var found = false, scan_this = !(fn instanceof AST_Arrow);
+                arg.walk(new TreeWalker(function(node, descend) {
                     if (found) return true;
                     if (node instanceof AST_SymbolRef && fn.variables.has(node.name)) {
                         var s = node.definition().scope;
@@ -860,11 +860,17 @@ merge(Compressor.prototype, {
                         }
                         return found = true;
                     }
-                    if (node instanceof AST_This && !tw.find_parent(AST_Scope)) {
+                    if (scan_this && node instanceof AST_This) {
                         return found = true;
                     }
-                });
-                arg.walk(tw);
+                    if (node instanceof AST_Scope && !(node instanceof AST_Arrow)) {
+                        var prev = scan_this;
+                        scan_this = false;
+                        descend();
+                        scan_this = prev;
+                        return true;
+                    }
+                }));
                 return found;
             }
 

test/compress/collapse_vars.js

@@ -2465,6 +2465,68 @@ issue_2203_2: {
     expect_stdout: "PASS"
 }
 
+issue_2203_3: {
+    options = {
+        collapse_vars: true,
+        unused: true,
+    }
+    input: {
+        a = "FAIL";
+        console.log({
+            a: "PASS",
+            b: function() {
+                return function(c) {
+                    return c.a;
+                }((String, (Object, (() => this)())));
+            }
+        }.b());
+    }
+    expect: {
+        a = "FAIL";
+        console.log({
+            a: "PASS",
+            b: function() {
+                return function(c) {
+                    return c.a;
+                }((String, (Object, (() => this)())));
+            }
+        }.b());
+    }
+    expect_stdout: "PASS"
+    node_version: ">=4"
+}
+
+issue_2203_4: {
+    options = {
+        collapse_vars: true,
+        unused: true,
+    }
+    input: {
+        a = "FAIL";
+        console.log({
+            a: "PASS",
+            b: function() {
+                return (c => {
+                    return c.a;
+                })((String, (Object, (() => this)())));
+            }
+        }.b());
+    }
+    expect: {
+        a = "FAIL";
+        console.log({
+            a: "PASS",
+            b: function() {
+                return (c => {
+                    return (String, (Object, (() => this)())).a;
+                })();
+            }
+        }.b());
+    }
+    expect_stdout: "PASS"
+    node_version: ">=4"
+}
+
 duplicate_argname: {
     options = {
         collapse_vars: true,