Improve error msgs when found type is deref of expected #82364

osa1 · 2021-02-21T10:30:42Z

This improves help messages in two cases:

When expected type is T and found type is &T, we now look through blocks
and suggest dereferencing the expression of the block, rather than the whole
block.
In the above case, if the expression is an &, we not suggest removing the
& instead of adding *.

Both of these are demonstrated in the regression test. Before this patch the
first error in the test would be:

error[E0308]: `if` and `else` have incompatible types
 --> test.rs:8:9
  |
5 | /     if true {
6 | |         a
  | |         - expected because of this
7 | |     } else {
8 | |         b
  | |         ^ expected `usize`, found `&usize`
9 | |     };
  | |_____- `if` and `else` have incompatible types
  |
help: consider dereferencing the borrow
  |
7 |     } else *{
8 |         b
9 |     };
  |

Now:

error[E0308]: `if` and `else` have incompatible types
 --> test.rs:8:9
  |
5 | /     if true {
6 | |         a
  | |         - expected because of this
7 | |     } else {
8 | |         b
  | |         ^
  | |         |
  | |         expected `usize`, found `&usize`
  | |         help: consider dereferencing the borrow: `*b`
9 | |     };
  | |_____- `if` and `else` have incompatible types

The second error:

error[E0308]: `if` and `else` have incompatible types
  --> test.rs:14:9
   |
11 | /     if true {
12 | |         1
   | |         - expected because of this
13 | |     } else {
14 | |         &1
   | |         ^^ expected integer, found `&{integer}`
15 | |     };
   | |_____- `if` and `else` have incompatible types
   |
help: consider dereferencing the borrow
   |
13 |     } else *{
14 |         &1
15 |     };
   |

now:

error[E0308]: `if` and `else` have incompatible types
  --> test.rs:14:9
   |
11 | /     if true {
12 | |         1
   | |         - expected because of this
13 | |     } else {
14 | |         &1
   | |         ^-
   | |         ||
   | |         |help: consider removing the `&`: `1`
   | |         expected integer, found `&{integer}`
15 | |     };
   | |_____- `if` and `else` have incompatible types

Fixes #82361

r? @estebank

compiler/rustc_typeck/src/check/demand.rs

estebank · 2021-02-22T00:23:03Z

@bors r+

bors · 2021-02-22T00:23:05Z

📌 Commit d2c0a4433c5d057ca93eb19d6e57dad4288728e5 has been approved by estebank

osa1 · 2021-02-22T15:56:22Z

@rustbot label: -S-waiting-on-bors +S-waiting-on-review

@estebank addressed your comment. Could you review again?

estebank

There's one minor change that is needed for the suggestion to be correct, otherwise <3.

src/test/ui/suggestions/issue-82361.stderr

compiler/rustc_typeck/src/check/demand.rs

src/test/ui/suggestions/issue-82361.rs

osa1 · 2021-02-22T20:31:35Z

@estebank all done

estebank · 2021-02-22T22:03:57Z

@bors r+

bors · 2021-02-22T22:03:59Z

📌 Commit b5ec7f36ce5394882b983f5368ac8da17e1d3a6d has been approved by estebank

bors · 2021-02-23T07:47:23Z

☔ The latest upstream changes (presumably #82430) made this pull request unmergeable. Please resolve the merge conflicts.

This improves help messages in two cases: - When expected type is `T` and found type is `&T`, we now look through blocks and suggest dereferencing the expression of the block, rather than the whole block. - In the above case, if the expression is an `&`, we not suggest removing the `&` instead of adding `*`. Both of these are demonstrated in the regression test. Before this patch the first error in the test would be: error[E0308]: `if` and `else` have incompatible types --> test.rs:8:9 | 5 | / if true { 6 | | a | | - expected because of this 7 | | } else { 8 | | b | | ^ expected `usize`, found `&usize` 9 | | }; | |_____- `if` and `else` have incompatible types | help: consider dereferencing the borrow | 7 | } else *{ 8 | b 9 | }; | Now: error[E0308]: `if` and `else` have incompatible types --> test.rs:8:9 | 5 | / if true { 6 | | a | | - expected because of this 7 | | } else { 8 | | b | | ^ | | | | | expected `usize`, found `&usize` | | help: consider dereferencing the borrow: `*b` 9 | | }; | |_____- `if` and `else` have incompatible types The second error: error[E0308]: `if` and `else` have incompatible types --> test.rs:14:9 | 11 | / if true { 12 | | 1 | | - expected because of this 13 | | } else { 14 | | &1 | | ^^ expected integer, found `&{integer}` 15 | | }; | |_____- `if` and `else` have incompatible types | help: consider dereferencing the borrow | 13 | } else *{ 14 | &1 15 | }; | now: error[E0308]: `if` and `else` have incompatible types --> test.rs:14:9 | 11 | / if true { 12 | | 1 | | - expected because of this 13 | | } else { 14 | | &1 | | ^- | | || | | |help: consider removing the `&`: `1` | | expected integer, found `&{integer}` 15 | | }; | |_____- `if` and `else` have incompatible types Fixes rust-lang#82361

osa1 · 2021-02-23T07:50:50Z

@estebank I had to rebase this so this needs another approval now :-(

osa1 · 2021-02-23T08:15:55Z

@rustbot label: -S-waiting-on-author +S-waiting-on-review

estebank · 2021-02-23T16:56:20Z

@bors r+

bors · 2021-02-23T16:56:22Z

📌 Commit fa74d48 has been approved by estebank

Improve error msgs when found type is deref of expected This improves help messages in two cases: - When expected type is `T` and found type is `&T`, we now look through blocks and suggest dereferencing the expression of the block, rather than the whole block. - In the above case, if the expression is an `&`, we not suggest removing the `&` instead of adding `*`. Both of these are demonstrated in the regression test. Before this patch the first error in the test would be: error[E0308]: `if` and `else` have incompatible types --> test.rs:8:9 | 5 | / if true { 6 | | a | | - expected because of this 7 | | } else { 8 | | b | | ^ expected `usize`, found `&usize` 9 | | }; | |_____- `if` and `else` have incompatible types | help: consider dereferencing the borrow | 7 | } else *{ 8 | b 9 | }; | Now: error[E0308]: `if` and `else` have incompatible types --> test.rs:8:9 | 5 | / if true { 6 | | a | | - expected because of this 7 | | } else { 8 | | b | | ^ | | | | | expected `usize`, found `&usize` | | help: consider dereferencing the borrow: `*b` 9 | | }; | |_____- `if` and `else` have incompatible types The second error: error[E0308]: `if` and `else` have incompatible types --> test.rs:14:9 | 11 | / if true { 12 | | 1 | | - expected because of this 13 | | } else { 14 | | &1 | | ^^ expected integer, found `&{integer}` 15 | | }; | |_____- `if` and `else` have incompatible types | help: consider dereferencing the borrow | 13 | } else *{ 14 | &1 15 | }; | now: error[E0308]: `if` and `else` have incompatible types --> test.rs:14:9 | 11 | / if true { 12 | | 1 | | - expected because of this 13 | | } else { 14 | | &1 | | ^- | | || | | |help: consider removing the `&`: `1` | | expected integer, found `&{integer}` 15 | | }; | |_____- `if` and `else` have incompatible types Fixes rust-lang#82361 --- r? `@estebank`

Improve error msgs when found type is deref of expected This improves help messages in two cases: - When expected type is `T` and found type is `&T`, we now look through blocks and suggest dereferencing the expression of the block, rather than the whole block. - In the above case, if the expression is an `&`, we not suggest removing the `&` instead of adding `*`. Both of these are demonstrated in the regression test. Before this patch the first error in the test would be: error[E0308]: `if` and `else` have incompatible types --> test.rs:8:9 | 5 | / if true { 6 | | a | | - expected because of this 7 | | } else { 8 | | b | | ^ expected `usize`, found `&usize` 9 | | }; | |_____- `if` and `else` have incompatible types | help: consider dereferencing the borrow | 7 | } else *{ 8 | b 9 | }; | Now: error[E0308]: `if` and `else` have incompatible types --> test.rs:8:9 | 5 | / if true { 6 | | a | | - expected because of this 7 | | } else { 8 | | b | | ^ | | | | | expected `usize`, found `&usize` | | help: consider dereferencing the borrow: `*b` 9 | | }; | |_____- `if` and `else` have incompatible types The second error: error[E0308]: `if` and `else` have incompatible types --> test.rs:14:9 | 11 | / if true { 12 | | 1 | | - expected because of this 13 | | } else { 14 | | &1 | | ^^ expected integer, found `&{integer}` 15 | | }; | |_____- `if` and `else` have incompatible types | help: consider dereferencing the borrow | 13 | } else *{ 14 | &1 15 | }; | now: error[E0308]: `if` and `else` have incompatible types --> test.rs:14:9 | 11 | / if true { 12 | | 1 | | - expected because of this 13 | | } else { 14 | | &1 | | ^- | | || | | |help: consider removing the `&`: `1` | | expected integer, found `&{integer}` 15 | | }; | |_____- `if` and `else` have incompatible types Fixes rust-lang#82361 --- r? ``@estebank``

Improve error msgs when found type is deref of expected This improves help messages in two cases: - When expected type is `T` and found type is `&T`, we now look through blocks and suggest dereferencing the expression of the block, rather than the whole block. - In the above case, if the expression is an `&`, we not suggest removing the `&` instead of adding `*`. Both of these are demonstrated in the regression test. Before this patch the first error in the test would be: error[E0308]: `if` and `else` have incompatible types --> test.rs:8:9 | 5 | / if true { 6 | | a | | - expected because of this 7 | | } else { 8 | | b | | ^ expected `usize`, found `&usize` 9 | | }; | |_____- `if` and `else` have incompatible types | help: consider dereferencing the borrow | 7 | } else *{ 8 | b 9 | }; | Now: error[E0308]: `if` and `else` have incompatible types --> test.rs:8:9 | 5 | / if true { 6 | | a | | - expected because of this 7 | | } else { 8 | | b | | ^ | | | | | expected `usize`, found `&usize` | | help: consider dereferencing the borrow: `*b` 9 | | }; | |_____- `if` and `else` have incompatible types The second error: error[E0308]: `if` and `else` have incompatible types --> test.rs:14:9 | 11 | / if true { 12 | | 1 | | - expected because of this 13 | | } else { 14 | | &1 | | ^^ expected integer, found `&{integer}` 15 | | }; | |_____- `if` and `else` have incompatible types | help: consider dereferencing the borrow | 13 | } else *{ 14 | &1 15 | }; | now: error[E0308]: `if` and `else` have incompatible types --> test.rs:14:9 | 11 | / if true { 12 | | 1 | | - expected because of this 13 | | } else { 14 | | &1 | | ^- | | || | | |help: consider removing the `&`: `1` | | expected integer, found `&{integer}` 15 | | }; | |_____- `if` and `else` have incompatible types Fixes rust-lang#82361 --- r? ```@estebank```

Rollup of 16 pull requests Successful merges: - rust-lang#75807 (Convert core/num/mod.rs to intra-doc links) - rust-lang#80534 (Use #[doc = include_str!()] in std) - rust-lang#80553 (Add an impl of Error on `Arc<impl Error>`.) - rust-lang#81167 (Make ptr::write const) - rust-lang#81575 (rustdoc: Name fields of `ResolutionFailure::WrongNamespace`) - rust-lang#81713 (Account for associated consts in the "unstable assoc item name colission" lint) - rust-lang#82078 (Make char and u8 methods const) - rust-lang#82087 (Fix ICE caused by suggestion with no code substitutions) - rust-lang#82090 (Do not consider using a semicolon inside of a different-crate macro) - rust-lang#82213 (Slices for vecs) - rust-lang#82214 (Remove redundant to_string calls) - rust-lang#82220 (fix the false 'defined here' messages) - rust-lang#82313 (Update normalize.css to 8.0.1) - rust-lang#82321 (AST: Remove some unnecessary boxes) - rust-lang#82364 (Improve error msgs when found type is deref of expected) - rust-lang#82514 (Update Clippy) Failed merges: r? `@ghost` `@rustbot` modify labels: rollup

rust-highfive assigned estebank Feb 21, 2021

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Feb 21, 2021

osa1 force-pushed the issue82361 branch from 0e398bb to d2c0a44 Compare February 21, 2021 10:33

estebank approved these changes Feb 22, 2021

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osa1 force-pushed the issue82361 branch from d2c0a44 to e55f3c5 Compare February 22, 2021 15:55

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osa1 force-pushed the issue82361 branch from e55f3c5 to b5ec7f3 Compare February 22, 2021 20:30

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camelid added A-diagnostics Area: Messages for errors, warnings, and lints A-suggestion-diagnostics Area: Suggestions generated by the compiler applied by `cargo fix` labels Feb 22, 2021

bors added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Feb 23, 2021

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Dylan-DPC-zz mentioned this pull request Feb 24, 2021

Rollup of 14 pull requests #82458

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Dylan-DPC-zz mentioned this pull request Feb 24, 2021

Rollup of 14 pull requests #82460

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Dylan-DPC-zz mentioned this pull request Feb 24, 2021

Rollup of 13 pull requests #82481

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Dylan-DPC-zz mentioned this pull request Feb 25, 2021

Rollup of 16 pull requests #82517

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bors merged commit 12ea0f6 into rust-lang:master Feb 25, 2021

rustbot added this to the 1.52.0 milestone Feb 25, 2021

osa1 deleted the issue82361 branch February 26, 2021 04:51

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Improve error msgs when found type is deref of expected #82364

Improve error msgs when found type is deref of expected #82364

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Improve error msgs when found type is deref of expected #82364

Improve error msgs when found type is deref of expected #82364

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