2017-08-14 17:21:36 -05:00
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error[E0308]: mismatched types
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--> $DIR/deref-suggestion.rs:18:9
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2018-02-22 18:42:32 -06:00
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LL | foo(s); //~ ERROR mismatched types
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type error method suggestions use whitelisted identity-like conversions
Previously, on a type mismatch (and if this wasn't preëmpted by a
higher-priority suggestion), we would look for argumentless methods
returning the expected type, and list them in a `help` note.
This had two major shortcomings. Firstly, a lot of the suggestions didn't
really make sense (if you used a &str where a String was expected,
`.to_ascii_uppercase()` is probably not the solution you were hoping
for). Secondly, we weren't generating suggestions from the most useful
traits!
We address the first problem with an internal
`#[rustc_conversion_suggestion]` attribute meant to mark methods that keep
the "same value" in the relevant sense, just converting the type. We
address the second problem by making `FnCtxt.probe_for_return_type` pass
the `ProbeScope::AllTraits` to `probe_op`: this would seem to be safe
because grep reveals no other callers of `probe_for_return_type`.
Also, structured suggestions are preferred (because they're pretty, but
also for RLS and friends).
Also also, we make the E0055 autoderef recursion limit error use the
one-time-diagnostics set, because we can potentially hit the limit a lot
during probing. (Without this,
test/ui/did_you_mean/recursion_limit_deref.rs would report "aborting due to
51 errors").
Unfortunately, the trait probing is still not all one would hope for: at a
minimum, we don't know how to rule out `into()` in cases where it wouldn't
actually work, and we don't know how to rule in `.to_owned()` where it
would. Issues #46459 and #46460 have been filed and are ref'd in a FIXME.
This is hoped to resolve #42929, #44672, and #45777.
2017-11-19 13:25:35 -06:00
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| ^
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| |
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| expected struct `std::string::String`, found reference
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| help: try using a conversion method: `s.to_string()`
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2017-08-14 17:21:36 -05:00
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= note: expected type `std::string::String`
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found type `&std::string::String`
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error[E0308]: mismatched types
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--> $DIR/deref-suggestion.rs:23:10
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2018-02-22 18:42:32 -06:00
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LL | foo3(u); //~ ERROR mismatched types
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2017-11-25 08:00:26 -06:00
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| ^
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| |
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| expected u32, found &u32
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| help: consider dereferencing the borrow: `*u`
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2017-08-14 17:21:36 -05:00
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= note: expected type `u32`
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found type `&u32`
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error[E0308]: mismatched types
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--> $DIR/deref-suggestion.rs:30:9
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2018-02-22 18:42:32 -06:00
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LL | foo(&"aaa".to_owned()); //~ ERROR mismatched types
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2017-11-25 08:00:26 -06:00
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| ^^^^^^^^^^^^^^^^^
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| |
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| expected struct `std::string::String`, found reference
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| help: consider removing the borrow: `"aaa".to_owned()`
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2017-08-14 17:21:36 -05:00
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= note: expected type `std::string::String`
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found type `&std::string::String`
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error[E0308]: mismatched types
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--> $DIR/deref-suggestion.rs:31:9
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2018-02-22 18:42:32 -06:00
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LL | foo(&mut "aaa".to_owned()); //~ ERROR mismatched types
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2017-11-25 08:00:26 -06:00
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| ^^^^^^^^^^^^^^^^^^^^^
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| |
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| expected struct `std::string::String`, found mutable reference
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| help: consider removing the borrow: `"aaa".to_owned()`
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2017-08-14 17:21:36 -05:00
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= note: expected type `std::string::String`
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found type `&mut std::string::String`
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error[E0308]: mismatched types
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--> $DIR/deref-suggestion.rs:12:20
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2018-02-22 18:42:32 -06:00
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LL | ($x:expr) => { &$x } //~ ERROR mismatched types
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2017-08-14 17:21:36 -05:00
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| ^^^ expected u32, found &{integer}
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...
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2018-02-22 18:42:32 -06:00
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LL | foo3(borrow!(0));
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2017-08-14 17:21:36 -05:00
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| ---------- in this macro invocation
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= note: expected type `u32`
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found type `&{integer}`
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error: aborting due to 5 previous errors
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2018-03-03 08:59:40 -06:00
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For more information about this error, try `rustc --explain E0308`.
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