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Auto merge of #85596 - scottmcm:more-on-unimplemented, r=estebank

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Extend `rustc_on_implemented` to improve more `?` error messages

`_Self` could match the generic definition; this adds that functionality for matching the generic definition of type parameters too.

Your advice welcome on the wording of all these messages, and which things belong in the message/label/note.

r? `@estebank`
This commit is contained in:
bors 2021-05-24 15:24:38 +00:00
commit ef0ec303fa
5 changed files with 47 additions and 15 deletions
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9
compiler/rustc_trait_selection/src/traits/error_reporting/on_unimplemented.rs
View File

@ -186,6 +186,15 @@ fn on_unimplemented_note(
};
let name = param.name;
flags.push((name, Some(value)));
if let GenericParamDefKind::Type { .. } = param.kind {
let param_ty = trait_ref.substs[param.index as usize].expect_ty();
if let Some(def) = param_ty.ty_adt_def() {
// We also want to be able to select the parameter's
// original signature with no type arguments resolved
flags.push((name, Some(self.tcx.type_of(def.did).to_string())));
}
}
}
if let Some(true) = self_ty.ty_adt_def().map(|def| def.did.is_local()) {

29
library/core/src/ops/try_trait.rs
View File

@ -254,6 +254,18 @@ pub trait Try: FromResidual {
label = "this `?` produces `{R}`, which is incompatible with `{Self}`",
enclosing_scope = "this function returns a `Result`"
),
on(
all(
from_method = "from_residual",
from_desugaring = "QuestionMark",
_Self = "std::option::Option<T>",
R = "std::result::Result<T, E>",
),
message = "the `?` operator can only be used on `Option`s, not `Result`s, \
in {ItemContext} that returns `Option`",
label = "use `.ok()?` if you want to discard the `{R}` error information",
enclosing_scope = "this function returns an `Option`"
),
on(
all(
from_method = "from_residual",
@ -272,13 +284,26 @@ pub trait Try: FromResidual {
from_method = "from_residual",
from_desugaring = "QuestionMark",
_Self = "std::ops::ControlFlow<B, C>",
R = "std::ops::ControlFlow<B, C>",
),
message = "the `?` operator can only be used on `ControlFlow<B, _>`s \
in {ItemContext} that returns `ControlFlow<B, _>`",
message = "the `?` operator in {ItemContext} that returns `ControlFlow<B, _>` \
can only be used on other `ControlFlow<B, _>`s (with the same Break type)",
label = "this `?` produces `{R}`, which is incompatible with `{Self}`",
enclosing_scope = "this function returns a `ControlFlow`",
note = "unlike `Result`, there's no `From`-conversion performed for `ControlFlow`"
),
on(
all(
from_method = "from_residual",
from_desugaring = "QuestionMark",
_Self = "std::ops::ControlFlow<B, C>",
// `R` is not a `ControlFlow`, as that case was matched previously
),
message = "the `?` operator can only be used on `ControlFlow`s \
in {ItemContext} that returns `ControlFlow`",
label = "this `?` produces `{R}`, which is incompatible with `{Self}`",
enclosing_scope = "this function returns a `ControlFlow`",
),
on(
all(
from_method = "from_residual",

8
src/test/ui/try-trait/bad-interconversion.rs
View File

@ -20,7 +20,7 @@ fn control_flow_to_result() -> Result<u64, String> {
fn result_to_option() -> Option<u16> {
Some(Err("hello")?)
//~^ ERROR the `?` operator can only be used on `Option`s in a function that returns `Option`
//~^ ERROR the `?` operator can only be used on `Option`s, not `Result`s, in a function that returns `Option`
}
fn control_flow_to_option() -> Option<u64> {
@ -30,18 +30,18 @@ fn control_flow_to_option() -> Option<u64> {
fn result_to_control_flow() -> ControlFlow<String> {
ControlFlow::Continue(Err("hello")?)
//~^ ERROR the `?` operator can only be used on `ControlFlow<B, _>`s in a function that returns `ControlFlow<B, _>`
//~^ ERROR the `?` operator can only be used on `ControlFlow`s in a function that returns `ControlFlow`
}
fn option_to_control_flow() -> ControlFlow<u64> {
Some(3)?;
//~^ ERROR the `?` operator can only be used on `ControlFlow<B, _>`s in a function that returns `ControlFlow<B, _>`
//~^ ERROR the `?` operator can only be used on `ControlFlow`s in a function that returns `ControlFlow`
ControlFlow::Break(10)
}
fn control_flow_to_control_flow() -> ControlFlow<i64> {
ControlFlow::Break(4_u8)?;
//~^ ERROR the `?` operator can only be used on `ControlFlow<B, _>`s in a function that returns `ControlFlow<B, _>`
//~^ ERROR the `?` operator in a function that returns `ControlFlow<B, _>` can only be used on other `ControlFlow<B, _>`s
ControlFlow::Continue(())
}

12
src/test/ui/try-trait/bad-interconversion.stderr
View File

@ -40,12 +40,12 @@ LL | | }
= help: the trait `FromResidual<ControlFlow<{integer}, Infallible>>` is not implemented for `Result<u64, String>`
= note: required by `from_residual`
error[E0277]: the `?` operator can only be used on `Option`s in a function that returns `Option`
error[E0277]: the `?` operator can only be used on `Option`s, not `Result`s, in a function that returns `Option`
--> $DIR/bad-interconversion.rs:22:22
|
LL | / fn result_to_option() -> Option<u16> {
LL | | Some(Err("hello")?)
| | ^ this `?` produces `Result<Infallible, &str>`, which is incompatible with `Option<u16>`
| | ^ use `.ok()?` if you want to discard the `Result<Infallible, &str>` error information
LL | |
LL | | }
| |_- this function returns an `Option`
@ -66,7 +66,7 @@ LL | | }
= help: the trait `FromResidual<ControlFlow<{integer}, Infallible>>` is not implemented for `Option<u64>`
= note: required by `from_residual`
error[E0277]: the `?` operator can only be used on `ControlFlow<B, _>`s in a function that returns `ControlFlow<B, _>`
error[E0277]: the `?` operator can only be used on `ControlFlow`s in a function that returns `ControlFlow`
--> $DIR/bad-interconversion.rs:32:39
|
LL | / fn result_to_control_flow() -> ControlFlow<String> {
@ -77,10 +77,9 @@ LL | | }
| |_- this function returns a `ControlFlow`
|
= help: the trait `FromResidual<Result<Infallible, &str>>` is not implemented for `ControlFlow<String>`
= note: unlike `Result`, there's no `From`-conversion performed for `ControlFlow`
= note: required by `from_residual`
error[E0277]: the `?` operator can only be used on `ControlFlow<B, _>`s in a function that returns `ControlFlow<B, _>`
error[E0277]: the `?` operator can only be used on `ControlFlow`s in a function that returns `ControlFlow`
--> $DIR/bad-interconversion.rs:37:12
|
LL | / fn option_to_control_flow() -> ControlFlow<u64> {
@ -92,10 +91,9 @@ LL | | }
| |_- this function returns a `ControlFlow`
|
= help: the trait `FromResidual<Option<Infallible>>` is not implemented for `ControlFlow<u64>`
= note: unlike `Result`, there's no `From`-conversion performed for `ControlFlow`
= note: required by `from_residual`
error[E0277]: the `?` operator can only be used on `ControlFlow<B, _>`s in a function that returns `ControlFlow<B, _>`
error[E0277]: the `?` operator in a function that returns `ControlFlow<B, _>` can only be used on other `ControlFlow<B, _>`s (with the same Break type)
--> $DIR/bad-interconversion.rs:43:29
|
LL | / fn control_flow_to_control_flow() -> ControlFlow<i64> {

4
src/test/ui/try-trait/option-to-result.stderr
View File

@ -12,13 +12,13 @@ LL | | }
= help: the trait `FromResidual<Option<Infallible>>` is not implemented for `Result<(), ()>`
= note: required by `from_residual`
error[E0277]: the `?` operator can only be used on `Option`s in a function that returns `Option`
error[E0277]: the `?` operator can only be used on `Option`s, not `Result`s, in a function that returns `Option`
--> $DIR/option-to-result.rs:11:6
|
LL | / fn test_option() -> Option<i32>{
LL | | let a:Result<i32, i32> = Ok(5);
LL | | a?;
| | ^ this `?` produces `Result<Infallible, i32>`, which is incompatible with `Option<i32>`
| | ^ use `.ok()?` if you want to discard the `Result<Infallible, i32>` error information
LL | | Some(5)
LL | | }
| |_- this function returns an `Option`