fix #27256, track type bounds for generic functions

pkg/dev_compiler/test/codegen_expected/closure.js

 export const closure = Object.create(null);
 import { core, js, dart, dartx } from 'dart_sdk';
-let dynamic__Toint = () => (dynamic__Toint = dart.constFn(dart.functionType(core.int, [dart.dynamic], [dart.dynamic])))();
-let dynamic__Todynamic = () => (dynamic__Todynamic = dart.constFn(dart.functionType(dart.dynamic, [dart.dynamic], {y: core.String, z: dart.dynamic})))();
-let StringToList = () => (StringToList = dart.constFn(dart.functionType(core.List, [core.String])))();
+let dynamic__Toint = () => (dynamic__Toint = dart.constFn(dart.fnTypeFuzzy(core.int, [dart.dynamic], [dart.dynamic])))();
+let dynamic__Todynamic = () => (dynamic__Todynamic = dart.constFn(dart.fnTypeFuzzy(dart.dynamic, [dart.dynamic], {y: core.String, z: dart.dynamic})))();
+let StringToList = () => (StringToList = dart.constFn(dart.fnTypeFuzzy(core.List, [core.String])))();
 let ListOfint = () => (ListOfint = dart.constFn(core.List$(core.int)))();
-let dynamicTodynamic = () => (dynamicTodynamic = dart.constFn(dart.functionType(dart.dynamic, [dart.dynamic])))();
-let FnToListOfint = () => (FnToListOfint = dart.constFn(dart.functionType(ListOfint(), [dynamicTodynamic()])))();
+let dynamicTodynamic = () => (dynamicTodynamic = dart.constFn(dart.fnTypeFuzzy(dart.dynamic, [dart.dynamic])))();
+let FnToListOfint = () => (FnToListOfint = dart.constFn(dart.fnTypeFuzzy(ListOfint(), [dynamicTodynamic()])))();
 let MapOfMap$Map = () => (MapOfMap$Map = dart.constFn(core.Map$(core.Map, core.Map)))();
 let Foo = () => (Foo = dart.constFn(closure.Foo$()))();
-let ListOfTAndTToListOfT = () => (ListOfTAndTToListOfT = dart.constFn(dart.definiteFunctionType(T => [core.List$(T), [core.List$(T), T]])))();
-let dynamicTovoid = () => (dynamicTovoid = dart.constFn(dart.definiteFunctionType(dart.void, [dart.dynamic])))();
-let VoidToNull = () => (VoidToNull = dart.constFn(dart.definiteFunctionType(core.Null, [])))();
+let ListOfTAndTToListOfT = () => (ListOfTAndTToListOfT = dart.constFn(dart.gFnType(T => [core.List$(T), [core.List$(T), T]])))();
+let dynamicTovoid = () => (dynamicTovoid = dart.constFn(dart.fnType(dart.void, [dart.dynamic])))();
+let VoidToNull = () => (VoidToNull = dart.constFn(dart.fnType(core.Null, [])))();
 closure.generic_function = function(T) {
   return (items: core.List<T>, seed: T): core.List<T> => {
-    let strings = items[dartx.map](core.String)(dart.fn((i: T): string => dart.str`${i}`, dart.definiteFunctionType(core.String, [T])))[dartx.toList]();
+    let strings = items[dartx.map](core.String)(dart.fn((i: T): string => dart.str`${i}`, dart.fnType(core.String, [T])))[dartx.toList]();
     return items;
   };
 };
 dart.fn(closure.generic_function, ListOfTAndTToListOfT());
-closure.Callback = dart.typedef('Callback', () => dart.functionType(dart.void, [], {i: core.int}));
+closure.Callback = dart.typedef('Callback', () => dart.fnTypeFuzzy(dart.void, [], {i: core.int}));
 closure.Foo$ = dart.generic(T => {
   let FooOfT = () => (FooOfT = dart.constFn(closure.Foo$(T)))();
   class Foo<T> extends core.Object {
     i: number;
     b: boolean;
     s: string;
     v: T;
     static some_static_constant: string;
     static some_static_final: string;
     static some_static_var: string;
@@ skipping 59 matching lines @@
   const b = Symbol("Foo.b");
   const s = Symbol("Foo.s");
   const v$ = Symbol("Foo.v");
   dart.setSignature(Foo, {
     fields: () => ({
       i: dart.finalFieldType(core.int),
       b: dart.fieldType(core.bool),
       s: dart.fieldType(core.String),
       v: dart.fieldType(T)
     }),
-    getters: () => ({prop: dart.definiteFunctionType(core.String, [])}),
-    setters: () => ({prop: dart.definiteFunctionType(dart.void, [core.String])}),
+    getters: () => ({prop: dart.fnType(core.String, [])}),
+    setters: () => ({prop: dart.fnType(dart.void, [core.String])}),
     methods: () => ({
-      untyped_method: dart.definiteFunctionType(dart.dynamic, [dart.dynamic, dart.dynamic]),
-      pass: dart.definiteFunctionType(T, [T]),
-      typed_method: dart.definiteFunctionType(core.String, [closure.Foo, core.List, core.int, core.num, core.double, core.bool, core.String, js.JsArray, js.JsObject, js.JsFunction]),
-      optional_params: dart.definiteFunctionType(dart.dynamic, [dart.dynamic], [dart.dynamic, core.int]),
-      nullary_method: dart.definiteFunctionType(dart.dynamic, []),
-      function_params: dart.definiteFunctionType(dart.dynamic, [dynamic__Toint(), dynamic__Todynamic(), closure.Callback]),
-      run: dart.definiteFunctionType(dart.dynamic, [core.List, core.String, StringToList(), FnToListOfint()], {h: MapOfMap$Map()})
+      untyped_method: dart.fnType(dart.dynamic, [dart.dynamic, dart.dynamic]),
+      pass: dart.fnType(T, [T]),
+      typed_method: dart.fnType(core.String, [closure.Foo, core.List, core.int, core.num, core.double, core.bool, core.String, js.JsArray, js.JsObject, js.JsFunction]),
+      optional_params: dart.fnType(dart.dynamic, [dart.dynamic], [dart.dynamic, core.int]),
+      nullary_method: dart.fnType(dart.dynamic, []),
+      function_params: dart.fnType(dart.dynamic, [dynamic__Toint(), dynamic__Todynamic(), closure.Callback]),
+      run: dart.fnType(dart.dynamic, [core.List, core.String, StringToList(), FnToListOfint()], {h: MapOfMap$Map()})
     }),
-    statics: () => ({named_params: dart.definiteFunctionType(dart.dynamic, [dart.dynamic], {b: dart.dynamic, c: core.int})}),
+    statics: () => ({named_params: dart.fnType(dart.dynamic, [dart.dynamic], {b: dart.dynamic, c: core.int})}),
     names: ['named_params']
   });
   return Foo;
 });
 closure.Foo = Foo();
 dart.defineLazy(closure.Foo, {
   get some_static_constant() {
     return "abc";
   },
   get some_static_final() {
@@ skipping 28 matching lines @@
     return "abc";
   },
   get some_top_level_var() {
     return "abc";
   },
   set some_top_level_var(_) {}
 });
 dart.trackLibraries("closure", {
   "closure.dart": closure
 }, null);