Problem inferring generic types only used in returns

[xunilrj]

predicate;

use std::inputs::input_predicate_data;

fn main() -> bool {
    let input: bool = input_predicate_data(0);
    input == true
}

This generates the following error:

          2936 | 
          2937 | pub trait AbiDecode {
          2938 |     fn abi_decode(ref mut buffer: BufferReader) -> Self;
               |        ^^^^^^^^^^ Internal compiler error: Method abi_decode_5 is a trait method dummy and was not properly replaced.
          Please file an issue on the repository and include the code that triggered this error.
          2939 | }

But the fully typed, and even the explicit version works fine

let input = input_predicate_data::<bool>(0);

[xunilrj]

I think the issue is that at instantiate_function_application, we do not check for unbound generic arguments. Nor do we check for generic arguments never solved later.

This example compiles, and runs!

script;

fn input_predicate_data2<T> () -> bool {
    true
}

fn main() -> bool {
    let input: bool = input_predicate_data2();
    input == true
}

rustc gives the correct error:

error[E0282]: type annotations needed
 --> src/main.rs:6:23
  |
6 |     let input: bool = input_predicate_data2();
  |                       ^^^^^^^^^^^^^^^^^^^^^ cannot infer type of the type parameter `T` declared on the function `input_predicate_data2`
  |
help: consider specifying the generic argument
  |
6 |     let input: bool = input_predicate_data2::<T>();
  |                                            +++++