Hint correct extern constant syntax
Error message for `extern "C" { const …}` is terse, and the right syntax is hard to guess given unfortunate difference between meaning of `static` in C and Rust.
I've added a hint for the right syntax.
rustc: Rearchitect lints to be emitted more eagerly
In preparation for incremental compilation this commit refactors the lint
handling infrastructure in the compiler to be more "eager" and overall more
incremental-friendly. Many passes of the compiler can emit lints at various
points but before this commit all lints were buffered in a table to be emitted
at the very end of compilation. This commit changes these lints to be emitted
immediately during compilation using pre-calculated lint level-related data
structures.
Linting today is split into two phases, one set of "early" lints run on the
`syntax::ast` and a "late" set of lints run on the HIR. This commit moves the
"early" lints to running as late as possible in compilation, just before HIR
lowering. This notably means that we're catching resolve-related lints just
before HIR lowering. The early linting remains a pass very similar to how it was
before, maintaining context of the current lint level as it walks the tree.
Post-HIR, however, linting is structured as a method on the `TyCtxt` which
transitively executes a query to calculate lint levels. Each request to lint on
a `TyCtxt` will query the entire crate's 'lint level data structure' and then go
from there about whether the lint should be emitted or not.
The query depends on the entire HIR crate but should be very quick to calculate
(just a quick walk of the HIR) and the red-green system should notice that the
lint level data structure rarely changes, and should hopefully preserve
incrementality.
Overall this resulted in a pretty big change to the test suite now that lints
are emitted much earlier in compilation (on-demand vs only at the end). This in
turn necessitated the addition of many `#![allow(warnings)]` directives
throughout the compile-fail test suite and a number of updates to the UI test
suite.
Closes https://github.com/rust-lang/rust/issues/42511
Point at return type always when type mismatch against it
Before this, the diagnostic errors would only point at the return type
when changing it would be a possible solution to a type error. Add a
label to the return type without a suggestion to change in order to make
the source of the expected type obvious.
Follow up to #42850, fixes#25133, fixes#41897.
In preparation for incremental compilation this commit refactors the lint
handling infrastructure in the compiler to be more "eager" and overall more
incremental-friendly. Many passes of the compiler can emit lints at various
points but before this commit all lints were buffered in a table to be emitted
at the very end of compilation. This commit changes these lints to be emitted
immediately during compilation using pre-calculated lint level-related data
structures.
Linting today is split into two phases, one set of "early" lints run on the
`syntax::ast` and a "late" set of lints run on the HIR. This commit moves the
"early" lints to running as late as possible in compilation, just before HIR
lowering. This notably means that we're catching resolve-related lints just
before HIR lowering. The early linting remains a pass very similar to how it was
before, maintaining context of the current lint level as it walks the tree.
Post-HIR, however, linting is structured as a method on the `TyCtxt` which
transitively executes a query to calculate lint levels. Each request to lint on
a `TyCtxt` will query the entire crate's 'lint level data structure' and then go
from there about whether the lint should be emitted or not.
The query depends on the entire HIR crate but should be very quick to calculate
(just a quick walk of the HIR) and the red-green system should notice that the
lint level data structure rarely changes, and should hopefully preserve
incrementality.
Overall this resulted in a pretty big change to the test suite now that lints
are emitted much earlier in compilation (on-demand vs only at the end). This in
turn necessitated the addition of many `#![allow(warnings)]` directives
throughout the compile-fail test suite and a number of updates to the UI test
suite.
Add a more precise error message for issue #35976
When trying to perform static dispatch on something which derefs to a trait object, and the target trait is not in scope, we had confusing error messages if the target method had a `Self: Sized` bound. We add a more precise error message in this case: "consider using trait ...".
Fixes#35976.
r? @nikomatsakis
field does not exist error: note fields if Levenshtein suggestion fails
When trying to access or initialize a nonexistent field, if we can't infer what
field was meant (by virtue of the purported field in the source being a small
Levenshtein distance away from an actual field, suggestive of a typo), issue a
note listing all the available fields. To reduce terminal clutter, we don't
issue the note when we have a `find_best_match_for_name` Levenshtein
suggestion: the suggestion is probably right.
The third argument of the call to `find_best_match_for_name` is changed to
`None`, accepting the default maximum Levenshtein distance of one-third of the
identifier supplied for correction. The previous value of `Some(name.len())`
was overzealous, inappropriately very Levenshtein-distant suggestions when the
attempted field access could not plausibly be a mere typo. For example, if a
struct has fields `mule` and `phone`, but I type `.donkey`, I'd rather the
error have a note listing that the available fields are, in fact, `mule` and
`phone` (which is the behavior induced by this patch) rather than the error
asking "did you mean `phone`?" (which is the behavior on master). The "only
find fits with at least one matching letter" comment was accurate when it was
first introduced in 09d992471 (January 2015), but is a vicious lie in its
present context before a call to `find_best_match_for_name` and must be
destroyed (replacing every letter is within a Levenshtein distance of name.len()).
The present author claims that this suffices to resolve#42599.
trans::mir::constant - fix assignment error recovery
trans::mir::constant - fix assignment error recovery
We used to not store anything when the RHS of an assignment returned an error, which caused ICEs downstream.
Fixes#43197.
resolve: Try to fix instability in import suggestions
cc https://github.com/rust-lang/rust/pull/42033
`lookup_import_candidates` walks module graph in DFS order and skips modules that were already visited (which is correct because there can be cycles).
However it means that if we visited `std::prelude::v1::Result::Ok` first, we will never visit `std::result::Result::Ok` because `Result` will be skipped as already visited (note: enums are also modules here), and otherwise, if we visited `std::result::Result::Ok` first, we will never get to `std::prelude::v1::Result::Ok`.
What child module of `std` (`prelude` or `result`) we will visit first, depends on randomized hashing, so we have instability in diagnostics.
With this patch modules' children are visited in stable order in `lookup_import_candidates`, this should fix the issue, but let's see what Travis will say.
r? @oli-obk
Extended error message for mut borrow conflicts in loops
RFC issue: https://github.com/rust-lang/rfcs/issues/2080
The error message for multiple mutable borrows on the same value over loop iterations now makes it clear that the conflict comes from the borrow outlasting the loop. The wording of the error is based on the special case of the moved-value error for a value moved in a loop. Following the example of that error, the code remains the same for the special case.
This is mainly because I felt the current message is confusing in the loop case : https://github.com/rust-lang/rust/issues/43437. It's not clear that the two conflicting borrows are in different iterations of the loop, and instead it just looks like the compiler has an issue with a single line.
Point at path segment on module not found
Point at the correct path segment on a import statement where a module
doesn't exist.
New output:
```rust
error[E0432]: unresolved import `std::bar`
--> <anon>:1:10
|
1 | use std::bar::{foo1, foo2};
| ^^^ Could not find `bar` in `std`
```
instead of:
```rust
error[E0432]: unresolved import `std::bar::foo1`
--> <anon>:1:16
|
1 | use std::bar::{foo1, foo2};
| ^^^^ Could not find `bar` in `std`
error[E0432]: unresolved import `std::bar::foo2`
--> <anon>:1:22
|
1 | use std::bar::{foo1, foo2};
| ^^^^ Could not find `bar` in `std`
```
Fix#43040.
Make the "main" constructors of NonZero/Shared/Unique return Option
Per discussion in https://github.com/rust-lang/rust/issues/27730#issuecomment-303939441.
This is a breaking change to unstable APIs.
The old behavior is still available under the name `new_unchecked`. Note that only that one can be `const fn`, since `if` is currently not allowed in constant contexts.
In the case of `NonZero` this requires adding a new `is_zero` method to the `Zeroable` trait. I mildly dislike this, but it’s not much worse than having a `Zeroable` trait in the first place. `Zeroable` and `NonZero` are both unstable, this can be reworked later.
Before this, the diagnostic errors would only point at the return type
when changing it would be a possible solution to a type error. Add a
label to the return type without a suggestion to change in order to make
the source of the expected type obvious.
Follow up to #42850, fixes#25133, fixes#41897.
Point at the correct path segment on a import statement where a module
doesn't exist.
New output:
```rust
error[E0432]: unresolved import `std::bar`
--> <anon>:1:10
|
1 | use std::bar::{foo1, foo2};
| ^^^ Could not find `bar` in `std`
```
instead of:
```rust
error[E0432]: unresolved import `std::bar::foo1`
--> <anon>:1:16
|
1 | use std::bar::{foo1, foo2};
| ^^^^ Could not find `bar` in `std`
error[E0432]: unresolved import `std::bar::foo2`
--> <anon>:1:22
|
1 | use std::bar::{foo1, foo2};
| ^^^^ Could not find `bar` in `std`
```
When trying to access or initialize a nonexistent field, if we can't infer what
field was meant (by virtue of the purported field in the source being a small
Levenshtein distance away from an actual field, suggestive of a typo), issue a
note listing all the available fields. To reduce terminal clutter, we don't
issue the note when we have a `find_best_match_for_name` Levenshtein
suggestion: the suggestion is probably right.
The third argument of the call to `find_best_match_for_name` is changed to
`None`, accepting the default maximum Levenshtein distance of one-third of the
identifier supplied for correction. The previous value of `Some(name.len())`
was overzealous, inappropriately very Levenshtein-distant suggestions when the
attempted field access could not plausibly be a mere typo. For example, if a
struct has fields `mule` and `phone`, but I type `.donkey`, I'd rather the
error have a note listing that the available fields are, in fact, `mule` and
`phone` (which is the behavior induced by this patch) rather than the error
asking "did you mean `phone`?" (which is the behavior on master). The "only
find fits with at least one matching letter" comment was accurate when it was
first introduced in 09d992471 (January 2015), but is a vicious lie in its
present context before a call to `find_best_match_for_name` and must be
destroyed (replacing every letter is a Levenshtein distance of name.len()).
The present author claims that this suffices to resolve#42599.
Point at `:` when using it instead of `;`
When triggering type ascription in such a way that we can infer a
statement end was intended, add a suggestion for the change. Always
point out the reason for the expectation of a type is due to type
ascription.
Fix#42057, #41928.
