noImplicitAny option do not generate an error when the function generating this coercicion is passed as a function parameter.

[sledorze]

TypeScript Version:

1.9.0-dev.20160523-1.0

Code (with noImplicitAny option turned ON)

class Foo {

  identity<T>(x: T): T {
    return x
  }

  bar<T>(g: (a: T) => T): (a: T) => T {
    return g;
  }

  constructor() {
    let v = a => this.identity(a)
    let w = this.bar(a => this.identity(a))
  }
}

Expected behavior:

The line binding an expression to w should error stating that 'a' implicitely has an 'any' type
OR (better)
v and w should be polymorphic (and have type (a:T) => T

Actual behavior:

v and w both have type (a:{}) => {} AND only the expression of v generates an error stating that 'a' implicitly has an 'any' type. (noImplicitAny option turned on)

[mhegazy]

The current behavior looks right to me.

• a in let v = a => this.identity(a) implicitly has the type any,as there is no type annotation or a contextual type.
• v does not have the type any, it is (a:any) => any, and it is not implicit. so no error should be reported here.
• a in this.bar(a => this.identity(a)) has a contextual type, that is the result of the inference for T, which happens to get no useful type, so falls back to the {}. and a gets that. again nothing implicit about this. see Type inference defaults to '{}' in call sites. #5254 for this.
• w does not have the type any, it is (a:{}) => {}, and it is not implicit. so no error should be reported here.

i think #5254 is the real culprit and not implictAny warnings.