[Bug][move-compiler-v2] problems with errors about lambda types in test hide panics due to missing error checks

[brmataptos]

🐛 Bug

Comparing

• third_party/move/move-compiler/tests/move_check/typing/lambda.exp
• third_party/move/move-compiler-v2/tests/checking/typing/lambda.exp

We see:

• line 40: V2 describes the error as the actual type of action (|&T|) being different from the type which would be expected from the context in which it is used (|(&T, u64)|_). The user will be confused by this, since the entire expression is pointed to. This should be changed to clarify somehow:

        error: expected `|(&T, u64)|_` but found a value of type `|&T|`
           ┌─ tests/checking/typing/lambda.move:40:13
           │
        40 │             action(XVector::borrow(v, i), i); // expected to have wrong argument count
           │             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

• line 45: similarly confusing error message from V2
• line 61: V2 has a very confusing message, given that the previous line declares x: u64:

         error: cannot return `u64` from a function with result type `|integer|`
          ┌─ tests/checking/typing/lambda.move:61:9
          │
       61 │         x(1) // expected to be not a function
          │         ^^^^

• line 67 and 73: describe the error in terms of the internals of the type system, rather than the programmer's view. Better would be to special-case built-in operations like + and say something like: a value of reference type &integer is not allowed as an argument to operator +.

       error: reference type `&integer` is not allowed as a type argument (type was inferred)
          ┌─ tests/checking/typing/lambda.move:67:35
          │
       67 │         foreach(&v, |e| sum = sum + e) // expected to cannot infer type
          │                                   ^
          │
          = required by instantiating type parameter `T` of function `+`

• lines 77, 81, 84, 86. 89 have errors in V1 which are missing from the V2 case.
  • Removing earlier errors allows V2 to catch line 84, but others are missing
• commenting out the code at line 84 causes a panic in recursive_struct_checker.rs:105.

The following is the part of the test code that doesn't yield an error and falls through to panic:

    public fun lambda_not_allowed() {
        let _x = |i| i + 1; // expected lambda not allowed
    }

    struct FieldFunNotAllowed {
        f: |u64|u64, // expected lambda not allowed
    }

    public inline fun macro_result_lambda_not_allowed(): |u64| {  // expected lambda not allowed
        abort (1)
    }
    public fun fun_result_lambda_not_allowed(): |u64| {  // expected lambda not allowed
        abort (1)
    }