suppress inline of this (#2103)

fixes #2101

lib/compress.js

@@ -3209,10 +3209,15 @@ merge(Compressor.prototype, {
                         if (!value) return make_node(AST_Undefined, self);
                         value.walk(new TreeWalker(function(node) {
                             if (value === self) return true;
-                            if (node instanceof AST_SymbolRef && exp.variables.has(node.name)) {
+                            if (node instanceof AST_SymbolRef && matches(node.scope.find_variable(node))
+                                || node instanceof AST_This && matches(node)) {
                                 value = self;
                                 return true;
                             }
+
+                            function matches(ref) {
+                                return ref && ref.scope.parent_scope === fn.parent_scope;
+                            }
                         }));
                         if (value !== self) value = best_of(compressor, value, self);
                     } else {

test/compress/functions.js

@@ -365,3 +365,52 @@ issue_2097: {
     }
     expect_stdout: "1"
 }
+
+issue_2101: {
+    options = {
+        inline: true,
+    }
+    input: {
+        a = {};
+        console.log(function() {
+            return function() {
+                return this.a;
+            }();
+        }() === function() {
+            return a;
+        }());
+    }
+    expect: {
+        a = {};
+        console.log(function() {
+            return this.a;
+        }() === a);
+    }
+    expect_stdout: "true"
+}
+
+inner_ref: {
+    options = {
+        inline: true,
+        unused: true,
+    }
+    input: {
+        console.log(function(a) {
+            return function() {
+                return a;
+            }();
+        }(1), function(a) {
+            return function(a) {
+                return a;
+            }();
+        }(2));
+    }
+    expect: {
+        console.log(function(a) {
+            return a;
+        }(1), function(a) {
+            return a;
+        }());
+    }
+    expect_stdout: "1 undefined"
+}