Revert "Revert "fix #27256, track type bounds for generic functions""

pkg/dev_compiler/test/codegen_expected/map_keys.js

Index: pkg/dev_compiler/test/codegen_expected/map_keys.js
diff --git a/pkg/dev_compiler/test/codegen_expected/map_keys.js b/pkg/dev_compiler/test/codegen_expected/map_keys.js
index adb4bffa505f2f3883a60946a510015f108d27cd..652419b9906003f517b323f456d1805e83f1fbfa 100644
--- a/pkg/dev_compiler/test/codegen_expected/map_keys.js
+++ b/pkg/dev_compiler/test/codegen_expected/map_keys.js
@@ -5,7 +5,7 @@ define(['dart_sdk'], function(dart_sdk) {
   const dart = dart_sdk.dart;
   const dartx = dart_sdk.dartx;
   const map_keys = Object.create(null);
-  let VoidTodynamic = () => (VoidTodynamic = dart.constFn(dart.definiteFunctionType(dart.dynamic, [])))();
+  let VoidTodynamic = () => (VoidTodynamic = dart.constFn(dart.fnType(dart.dynamic, [])))();
   map_keys.main = function() {
     core.print(dart.map({'1': 2, '3': 4, '5': 6}, core.String, core.int));
     core.print(dart.map([1, 2, 3, 4, 5, 6], core.int, core.int));