Suggest calling await on method call and field access
When encountering a failing method or field resolution on a `Future`,
look at the `Output` and try the same operation on it. If successful,
suggest calling `.await` on the `Future`.
This had already been introduced in #72784, but at some point they
stopped working.
Built on top of #78214, only last commit is relevant.
r? @oli-obk
When encountering a failing method or field resolution on a `Future`,
look at the `Output` and try the same operation on it. If successful,
suggest calling `.await` on the `Future`.
This had already been introduced in #72784, but at some point they
stopped working.
Overhaul const-checking diagnostics
The primary purpose of this PR was to remove `NonConstOp::STOPS_CONST_CHECKING`, which causes any additional errors found by the const-checker to be silenced. I used this flag to preserve diagnostic parity with `qualify_min_const_fn.rs`, which has since been removed.
However, simply removing the flag caused a deluge of errors in some cases, since an error would be emitted any time a local or temporary had a wrong type. To remedy this, I added an alternative system (`DiagnosticImportance`) to silence additional error messages that were likely to distract the user from the underlying issue. When an error of the highest importance occurs, all less important errors are silenced. When no error of the highest importance occurs, all less important errors are emitted after checking is complete. Following the suggestions from the important error is usually enough to fix the less important errors, so this should lead to better UX most of the time.
There's also some unrelated diagnostics improvements in this PR isolated in their own commits. Splitting them out would be possible, but a bit of a pain. This isn't as tidy as some of my other PRs, but it should *only* affect diagnostics, never whether or not something passes const-checking. Note that there are a few trivial exceptions to this, like banning `Yield` in all const-contexts, not just `const fn`.
As always, meant to be reviewed commit-by-commit.
r? `@oli-obk`
If a symbol name can only be imported from one place for a type, and
as long as it was not glob-imported anywhere in the current crate, we
can trim its printed path and print only the name.
This has wide implications on error messages with types, for example,
shortening `std::vec::Vec` to just `Vec`, as long as there is no other
`Vec` importable anywhere.
This adds a new '-Z trim-diagnostic-paths=false' option to control this
feature.
On the good path, with no diagnosis printed, we should try to avoid
issuing this query, so we need to prevent trimmed_def_paths query on
several cases.
This change also relies on a previous commit that differentiates
between `Debug` and `Display` on various rustc types, where the latter
is trimmed and presented to the user and the former is not.
Await on mismatched future types
Closes#61076
This PR suggests to `await` on:
1. `async_fn().bar() => async_fn().await.bar()`
2. `async_fn().field => async_fn().await.field`
3. ` if let x = async() {} => if let x = async().await {}`
r? @tmandry @estebank
Be consistent when describing a move as a 'partial' in diagnostics
When an error occurs due to a partial move, we would use the world
"partial" in some parts of the error message, but not in others. This
commit ensures that we use the word 'partial' in either all or none of
the diagnostic messages.
Additionally, we no longer describe a move out of a `Box` via `*` as
a 'partial move'. This was a pre-existing issue, but became more
noticable when the word 'partial' is used in more places.
Currently, the def span of a funtion encompasses the entire function
signature and body. However, this is usually unnecessarily verbose - when we are
pointing at an entire function in a diagnostic, we almost always want to
point at the signature. The actual contents of the body tends to be
irrelevant to the diagnostic we are emitting, and just takes up
additional screen space.
This commit changes the `def_span` of all function items (freestanding
functions, `impl`-block methods, and `trait`-block methods) to be the
span of the signature. For example, the function
```rust
pub fn foo<T>(val: T) -> T { val }
```
now has a `def_span` corresponding to `pub fn foo<T>(val: T) -> T`
(everything before the opening curly brace).
Trait methods without a body have a `def_span` which includes the
trailing semicolon. For example:
```rust
trait Foo {
fn bar();
}```
the function definition `Foo::bar` has a `def_span` of `fn bar();`
This makes our diagnostic output much shorter, and emphasizes
information that is relevant to whatever diagnostic we are reporting.
We continue to use the full span (including the body) in a few of
places:
* MIR building uses the full span when building source scopes.
* 'Outlives suggestions' use the full span to sort the diagnostics being
emitted.
* The `#[rustc_on_unimplemented(enclosing_scope="in this scope")]`
attribute points the entire scope body.
* The 'unconditional recursion' lint uses the full span to show
additional context for the recursive call.
All of these cases work only with local items, so we don't need to
add anything extra to crate metadata.
When an error occurs due to a partial move, we would use the world
"partial" in some parts of the error message, but not in others. This
commit ensures that we use the word 'partial' in either all or none of
the diagnostic messages.
Additionally, we no longer describe a move out of a `Box` via `*` as
a 'partial move'. This was a pre-existing issue, but became more
noticable when the word 'partial' is used in more places.
expand: Stop using nonterminals for passing tokens to attribute and derive macros
Make one more step towards fully token-based expansion and fix issues described in https://github.com/rust-lang/rust/issues/72545#issuecomment-640276791.
Now `struct S;` is passed to `foo!(struct S;)` and `#[foo] struct S;` in the same way - as a token stream `struct S ;`, rather than a single non-terminal token `NtItem` which is then broken into parts later.
The cost is making pretty-printing of token streams less pretty.
Some of the pretty-printing regressions will be recovered by keeping jointness with each token, which we will need to do anyway.
Unfortunately, this is not exactly the same thing as https://github.com/rust-lang/rust/pull/73102.
One more observable effect is how `$crate` is printed in the attribute input.
Inside `NtItem` was printed as `crate` or `that_crate`, now as a part of a token stream it's printed as `$crate` (there are good reasons for these differences, see https://github.com/rust-lang/rust/pull/62393 and related PRs).
This may break old proc macros (custom derives) written before the main portion of the proc macro API (macros 1.2) was stabilized, those macros did `input.to_string()` and reparsed the result, now that result can contain `$crate` which cannot be reparsed.
So, I think we should do this regardless, but we need to run crater first.
r? @Aaron1011
Use an 'approximate' universal upper bound when reporting region errors
Fixes#67765
When reporting errors during MIR region inference, we sometimes use
`universal_upper_bound` to obtain a named universal region that we
can display to the user. However, this is not always possible - in a
case like `fn foo<'a, 'b>() { .. }`, the only upper bound for a region
containing `'a` and `'b` is `'static`. When displaying diagnostics, it's
usually better to display *some* named region (even if there are
multiple involved) rather than fall back to a generic error involving
`'static`.
This commit adds a new `approx_universal_upper_bound` method, which
uses the lowest-numbered universal region if the only alternative is to
return `'static`.
Fixes#67765
When reporting errors during MIR region inference, we sometimes use
`universal_upper_bound` to obtain a named universal region that we
can display to the user. However, this is not always possible - in a
case like `fn foo<'a, 'b>() { .. }`, the only upper bound for a region
containing `'a` and `'b` is `'static`. When displaying diagnostics, it's
usually better to display *some* named region (even if there are
multiple involved) rather than fall back to a generic error involving
`'static`.
This commit adds a new `approx_universal_upper_bound` method, which
uses the lowest-numbered universal region if the only alternative is to
return `'static`.
Display information about captured variable in `FnMut` error
Fixes#69446
When we encounter a region error involving an `FnMut` closure, we
display a specialized error message. However, we currently do not
tell the user which upvar was captured. This makes it difficult to
determine the cause of the error, especially when the closure is large.
This commit records marks constraints involving closure upvars
with `ConstraintCategory::ClosureUpvar`. When we decide to 'blame'
a `ConstraintCategory::Return`, we additionall store
the captured upvar if we found a `ConstraintCategory::ClosureUpvar` in
the path.
When generating an error message, we point to relevant spans if we have
closure upvar information available. We further customize the message if
an `async` closure is being returned, to make it clear that the captured
variable is being returned indirectly.
Allow inference regions when relating consts
As first noticed by @eddyb, `super_relate_consts` doesn't need to check for inference vars since `eval` does it already (and handles lifetimes correctly by erasing them).
Fixes#73050
r? @oli-obk
