bjoernager/rust
bjoernager/rust
1
Fork 0
Code Activity

Auto merge of #77354 - ecstatic-morse:const-checking-moar-errors, r=oli-obk

Browse source 
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`
This commit is contained in:
bors 2020-10-01 07:38:47 +00:00
commit fc42fb8e70
58 changed files with 594 additions and 607 deletions
Download patch file Download diff file Expand all files Collapse all files

2
compiler/rustc_error_codes/src/error_codes.rs
View file

@ -18,7 +18,6 @@ E0010: include_str!("./error_codes/E0010.md"),
E0013: include_str!("./error_codes/E0013.md"),
E0014: include_str!("./error_codes/E0014.md"),
E0015: include_str!("./error_codes/E0015.md"),
E0019: include_str!("./error_codes/E0019.md"),
E0023: include_str!("./error_codes/E0023.md"),
E0025: include_str!("./error_codes/E0025.md"),
E0026: include_str!("./error_codes/E0026.md"),
@ -463,6 +462,7 @@ E0776: include_str!("./error_codes/E0776.md"),
;
// E0006, // merged with E0005
// E0008, // cannot bind by-move into a pattern guard
// E0019, merged into E0015
// E0035, merged into E0087/E0089
// E0036, merged into E0087/E0089
// E0068,

36
compiler/rustc_error_codes/src/error_codes/E0019.md
View file

@ -1,36 +0,0 @@
A function call isn't allowed in the const's initialization expression
because the expression's value must be known at compile-time.
Erroneous code example:
```compile_fail,E0019
#![feature(box_syntax)]
fn main() {
struct MyOwned;
static STATIC11: Box<MyOwned> = box MyOwned; // error!
}
```
Remember: you can't use a function call inside a const's initialization
expression! However, you can totally use it anywhere else:
```
enum Test {
V1
}
impl Test {
fn func(&self) -> i32 {
12
}
}
fn main() {
const FOO: Test = Test::V1;
FOO.func(); // here is good
let x = FOO.func(); // or even here!
}
```