Fix is_const_context, update check_for_cast
#72380
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estebank
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| LL | let f = [0; -4_isize]; | ||
| | ^^^^^^^^ expected `usize`, found `isize` | ||
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| help: you can convert an `isize` to `usize` and panic if the converted value wouldn't fit | ||
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| LL | let f = [0; (-4_isize).try_into().unwrap()]; | ||
| | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | ||
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It'd be interesting if we could add a note saying that -4 can't fit in usize, but that's independent of this PR.
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@bors r+ |
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📌 Commit 6da17d2 has been approved by |
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RalfJung
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Fix `is_const_context`, update `check_for_cast` A better version of rust-lang#71477 Adds `fn enclosing_body_owner` and uses it in `is_const_context`. `is_const_context` now uses the same mechanism as `mir_const_qualif` as it was previously incorrect. Renames `is_const_context` to `is_inside_const_context`. I also updated `check_for_cast` in the second commit, so r? @estebank (I removed one lvl of indentation, so it might be easier to review by hiding whitespace changes)
bors
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Jun 11, 2020
Rollup of 11 pull requests Successful merges: - rust-lang#72380 (Fix `is_const_context`, update `check_for_cast`) - rust-lang#72941 (Ensure stack when building MIR for matches) - rust-lang#72976 (Clean up E0642 explanation) - rust-lang#73080 (doc/rustdoc: Fix incorrect external_doc feature flag) - rust-lang#73155 (save_analysis: better handle paths and functions signature) - rust-lang#73164 (Add new E0762 error code) - rust-lang#73172 (Fix more clippy warnings) - rust-lang#73181 (Automatically prioritize unsoundness issues) - rust-lang#73183 (Support proc macros in intra doc link resolution) - rust-lang#73208 (Fix doctest template) - rust-lang#73219 (x.py: with --json-output, forward cargo's JSON) Failed merges: r? @ghost
ayazhafiz
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Jun 13, 2020
re rust-lang#72380 (comment) Given the toy code ```rust fn is_positive(n: usize) { n > -1_isize; } ``` We currently get a type mismatch error like the following: ``` error[E0308]: mismatched types --> src/main.rs:2:9 | 2 | n > -1_isize; | ^^^^^^^^ expected `usize`, found `isize` | help: you can convert an `isize` to `usize` and panic if the converted value wouldn't fit | 2 | n > (-1_isize).try_into().unwrap(); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ``` But clearly, `-1` can never fit into a `usize`, so the suggestion will always panic. A more useful message would tell the user that the value can never fit in the expected type: ``` error[E0308]: mismatched types --> test.rs:2:9 | 2 | n > -1_isize; | ^^^^^^^^ expected `usize`, found `isize` | note: `-1_isize` can never fit into `usize` --> test.rs:2:9 | 2 | n > -1_isize; | ^^^^^^^^ ``` Which is what this commit implements. I only added this check for negative literals because - Currently we can only perform such a check for literals (constant value propagation is outside the scope of the typechecker at this point) - A lint error for out-of-range numeric literals is already emitted IMO it makes more sense to put this check in librustc_lint, but as far as I can tell the typecheck pass happens before the lint pass, so I've added it here. r? @estebank
Manishearth
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Jun 18, 2020
…r=estebank Note numeric literals that can never fit in an expected type re rust-lang#72380 (comment) Given the toy code ```rust fn is_positive(n: usize) { n > -1_isize; } ``` We currently get a type mismatch error like the following: ``` error[E0308]: mismatched types --> src/main.rs:2:9 | 2 | n > -1_isize; | ^^^^^^^^ expected `usize`, found `isize` | help: you can convert an `isize` to `usize` and panic if the converted value wouldn't fit | 2 | n > (-1_isize).try_into().unwrap(); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ``` But clearly, `-1` can never fit into a `usize`, so the suggestion will always panic. A more useful message would tell the user that the value can never fit in the expected type: ``` error[E0308]: mismatched types --> test.rs:2:9 | 2 | n > -1_isize; | ^^^^^^^^ expected `usize`, found `isize` | note: `-1_isize` can never fit into `usize` --> test.rs:2:9 | 2 | n > -1_isize; | ^^^^^^^^ ``` Which is what this commit implements. I only added this check for negative literals because - Currently we can only perform such a check for literals (constant value propagation is outside the scope of the typechecker at this point) - A lint error for out-of-range numeric literals is already emitted IMO it makes more sense to put this check in librustc_lint, but as far as I can tell the typecheck pass happens before the lint pass, so I've added it here. r? @estebank
Manishearth
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Jun 19, 2020
…r=estebank Note numeric literals that can never fit in an expected type re rust-lang#72380 (comment) Given the toy code ```rust fn is_positive(n: usize) { n > -1_isize; } ``` We currently get a type mismatch error like the following: ``` error[E0308]: mismatched types --> src/main.rs:2:9 | 2 | n > -1_isize; | ^^^^^^^^ expected `usize`, found `isize` | help: you can convert an `isize` to `usize` and panic if the converted value wouldn't fit | 2 | n > (-1_isize).try_into().unwrap(); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ``` But clearly, `-1` can never fit into a `usize`, so the suggestion will always panic. A more useful message would tell the user that the value can never fit in the expected type: ``` error[E0308]: mismatched types --> test.rs:2:9 | 2 | n > -1_isize; | ^^^^^^^^ expected `usize`, found `isize` | note: `-1_isize` can never fit into `usize` --> test.rs:2:9 | 2 | n > -1_isize; | ^^^^^^^^ ``` Which is what this commit implements. I only added this check for negative literals because - Currently we can only perform such a check for literals (constant value propagation is outside the scope of the typechecker at this point) - A lint error for out-of-range numeric literals is already emitted IMO it makes more sense to put this check in librustc_lint, but as far as I can tell the typecheck pass happens before the lint pass, so I've added it here. r? @estebank
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A better version of #71477
Adds
fn enclosing_body_ownerand uses it inis_const_context.is_const_contextnow uses the same mechanism asmir_const_qualifas it was previously incorrect.Renames
is_const_contexttois_inside_const_context.I also updated
check_for_castin the second commit, so r? @estebank(I removed one lvl of indentation, so it might be easier to review by hiding whitespace changes)