Array.prototype.filter.not.forcing.boolean.type

src/lib/es5.d.ts

@@ -1510,7 +1510,7 @@ interface Int8Array {
       * @param thisArg An object to which the this keyword can refer in the callbackfn function. 
       * If thisArg is omitted, undefined is used as the this value.
       */
-    filter(callbackfn: (value: number, index: number, array: Int8Array) => boolean, thisArg?: any): Int8Array;
+    filter(callbackfn: (value: number, index: number, array: Int8Array) => any, thisArg?: any): Int8Array;
 
     /** 
       * Returns the value of the first element in the array where predicate is true, and undefined 

tests/baselines/reference/arrayFilter.errors.txt

@@ -0,0 +1,15 @@
+tests/cases/compiler/arrayFilter.ts(7,12): error TS2345: Argument of type '(x: { name: string; }) => string' is not assignable to parameter of type '(value: { name: string; }, index: number, array: { name: string; }[]) => boolean'.
+  Type 'string' is not assignable to type 'boolean'.
+
+
+==== tests/cases/compiler/arrayFilter.ts (1 errors) ====
+    var foo = [
+       { name: 'bar' },
+       { name: null },
+       { name: 'baz' }
+    ]
+
+    foo.filter(x => x.name); //should accepted all possible types not only boolean!
+               ~~~~~~~~~~~
+!!! error TS2345: Argument of type '(x: { name: string; }) => string' is not assignable to parameter of type '(value: { name: string; }, index: number, array: { name: string; }[]) => boolean'.
+!!! error TS2345:   Type 'string' is not assignable to type 'boolean'.

tests/baselines/reference/arrayFilter.js

@@ -0,0 +1,16 @@
+//// [arrayFilter.ts]
+var foo = [
+   { name: 'bar' },
+   { name: null },
+   { name: 'baz' }
+]
+
+foo.filter(x => x.name); //should accepted all possible types not only boolean!
+
+//// [arrayFilter.js]
+var foo = [
+    { name: 'bar' },
+    { name: null },
+    { name: 'baz' }
+];
+foo.filter(function (x) { return x.name; }); //should accepted all possible types not only boolean!

tests/cases/compiler/arrayFilter.ts

@@ -0,0 +1,7 @@
+var foo = [
+   { name: 'bar' },
+   { name: null },
+   { name: 'baz' }
+]
+
+foo.filter(x => x.name); //should accepted all possible types not only boolean!