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Description
{This specific case originates from the following issue & comment: #47168 (comment) }
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I tried this code:
test(array.len());I expected to see this happen:
error[E0308]: mismatched types
--> src/main.rs:3:10
|
3 | test(array.len());
| ^^^^^^^^^^^ expected u32, found usize
help: you can convert an `usize` to `u32` or panic if it the converted value wouldn't fit
|
3 | use std::convert::TryInto;
4 | test(array.len().try_into().unwrap());
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
(Or similar.)
i.e. An error message that includes the required use line necessary for the suggestion to compile.
Instead, this happened:
error[E0308]: mismatched types
--> src/main.rs:3:10
|
3 | test(array.len());
| ^^^^^^^^^^^ expected u32, found usize
help: you can convert an `usize` to `u32` or panic if it the converted value wouldn't fit
|
3 | test(array.len().try_into().unwrap());
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
(Which would be fine if there is a pre-existing use std::convert::TryInto;.)
This meant that--after applying the suggested fix--when compiling I got another error relating to the suggested code:
error[E0599]: no method named `try_into` found for type `usize` in the current scope
--> src/main.rs:3:22
|
3 | test(array.len().try_into().unwrap());
| ^^^^^^^^
|
= help: items from traits can only be used if the trait is in scope
help: the following trait is implemented but not in scope, perhaps add a `use` for it:
|
1 | use std::convert::TryInto;
This was surprising to me because I thought the compiler diagnostics were magic & infallible . :D
Note: Example code & messages were copy & pasted from original issue.