Provide context for missing comma in match arm and if statement without block #48338

estebank · 2018-02-18T23:14:28Z

When finding:

match &Some(3) {
    &None => 1
    &Some(2) => { 3 }
    _ => 2
}

provide the following diagnostic:

error: expected one of `,`, `.`, `?`, `}`, or an operator, found `=>`
 --> $DIR/missing-comma-in-match.rs:15:18
  |
X |         &None => 1
  |               --  - help: missing comma
  |               |
  |               while parsing the match arm starting here
X |         &Some(2) => { 3 }
  |                  ^^ expected one of `,`, `.`, `?`, `}`, or an operator here

When unnecessarily using a fat arrow after an if condition, suggest the
removal of it.

error: expected `{`, found `=>`
  --> $DIR/missing-block-hint.rs:13:18
   |
13 |         if (foo) => {} //~ ERROR expected `{`, found `=>`
   |                  ^^ help: only necessary in match arms, not before if blocks

When finding an if statement with no block, point at the if keyword to
provide more context:


error: expected `{`, found `}`
  --> file.rs:6:1
   |
13 |     if 5 == {
   |     -- this `if` statement has a condition, but no block
...
17 | }
   | ^

Fix #29586, fix #30035.

rust-highfive · 2018-02-18T23:14:39Z

r? @pnkfelix

(rust_highfive has picked a reviewer for you, use r? to override)

estebank · 2018-02-19T06:38:30Z

r? @nikomatsakis

nikomatsakis · 2018-02-20T21:02:13Z

src/libsyntax/parse/parser.rs

+            if let Some(sp) = fat_arrow_sp {
+                // if cond => expr
+                err.span_suggestion(sp,
+                                    "only necessary in match arms, not before if blocks",


Nit: I found this confusingly phrased. Maybe this?

"only necessary with `match`, not `if`"

I'm also aiming to avoid jargon like "arms" and "blocks", which users may not be familiar with.

nikomatsakis · 2018-02-20T21:03:07Z

src/libsyntax/parse/parser.rs

+
+        let expr = self.parse_expr_res(Restrictions::STMT_EXPR, None)
+            .map_err(|mut err| {
+                err.span_label(arrow_span, "while parsing the match arm starting here");


I would say:

"while parsing the `match` arm starting here"

nikomatsakis · 2018-02-20T21:06:49Z

src/test/ui/suggestions/missing-comma-in-match.stderr

+13 |         &None => 1
+   |               --  - help: missing a comma here to end this match arm
+   |               |
+   |               while parsing the match arm starting here


I feel like this is "heavy", but I'm not sure how to suggest an improvement yet. I wonder if just the suggestion would be enough?

error: expected one of `,`, `.`, `?`, `}`, or an operator, found `=>` --> $DIR/missing-comma-in-match.rs:14:18 | 13 | &None => 1 | - help: maybe missing a comma here: `1,` 14 | &Some(2) => { 3 } | ^^ expected one of `,`, `.`, `?`, `}`, or an operator here error: aborting due to previous error

Would that be hard to add?

It shouldn't.

petrochenkov · 2018-02-21T19:29:38Z

src/libsyntax/parse/parser.rs

+        };
+        let thn = self.parse_block().map_err(|mut err| {
+            if let Some(sp) = fat_arrow_sp {
+                // if cond => expr


Is there an issue about this or any other confirmation that this mistake is realistic?

There was an existing test case, but it is indeed a big corner case. I can remove the special diagnostic.

Yes, I think just removing this would be for the better.

petrochenkov · 2018-02-21T19:30:04Z

LGTM except for maybe removing special diagnostics for https://github.com/rust-lang/rust/pull/48338/files#r169751541

petrochenkov · 2018-02-25T20:26:17Z

@bors r+

bors · 2018-02-25T20:26:17Z

📌 Commit 3e730aa has been approved by petrochenkov

bors · 2018-02-27T03:19:26Z

☔ The latest upstream changes (presumably #48449) made this pull request unmergeable. Please resolve the merge conflicts.

When finding: ```rust match &Some(3) { &None => 1 &Some(2) => { 3 } _ => 2 } ``` provide the following diagnostic: ``` error: expected one of `,`, `.`, `?`, `}`, or an operator, found `=>` --> $DIR/missing-comma-in-match.rs:15:18 | X | &None => 1 | -- - help: missing comma | | | while parsing the match arm starting here X | &Some(2) => { 3 } | ^^ expected one of `,`, `.`, `?`, `}`, or an operator here ```

When unnecessarily using a fat arrow after an if condition, suggest the removal of it. When finding an if statement with no block, point at the `if` keyword to provide more context.

nikomatsakis · 2018-02-27T19:53:13Z

@bors r=petrochenkov

bors · 2018-02-27T19:53:13Z

📌 Commit d63d363 has been approved by petrochenkov

bors · 2018-03-01T10:18:25Z

💔 Test failed - status-appveyor

kennytm · 2018-03-01T10:32:07Z

@bors retry #46903 (check i686-pc-windows-msvc)

34 minutes spent on building stage1-rustc.

bors · 2018-03-02T03:03:37Z

⌛ Testing commit 24be75d with merge b78bf234740ed8f040c8546e21d509fc137cb468...

Manishearth · 2018-03-02T03:07:09Z

@bors retry

(rollup priority)

bors · 2018-03-02T07:03:37Z

💥 Test timed out

petrochenkov · 2018-03-02T08:59:48Z

Looks like this hasn't landed as a part of rollup.

petrochenkov · 2018-03-02T09:00:12Z

@bors r+

bors · 2018-03-02T09:00:13Z

💡 This pull request was already approved, no need to approve it again.

This pull request previously failed. You should add more commits to fix the bug, or use retry to trigger a build again.
There's another pull request that is currently being tested, blocking this pull request: rust: Import LLD for linking wasm objects #48125

bors · 2018-03-02T09:00:13Z

📌 Commit 24be75d has been approved by petrochenkov

@nrc

…rochenkov Fixes rust-lang#47311. r? @nrc

@nrc

…rochenkov Fixes rust-lang#47311. r? @nrc

@nrc

…rochenkov Fixes rust-lang#47311. r? @nrc

rust-highfive assigned pnkfelix Feb 18, 2018

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Feb 18, 2018

estebank force-pushed the match-missing-comma branch 3 times, most recently from 8d880f5 to aabfe31 Compare February 19, 2018 06:31

estebank changed the title ~~Provide missing comma in match arm suggestion~~ Provide context for missing comma in match arm and if statement without block Feb 19, 2018

rust-highfive assigned nikomatsakis and unassigned pnkfelix Feb 19, 2018

petrochenkov self-assigned this Feb 19, 2018

nikomatsakis reviewed Feb 20, 2018

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petrochenkov reviewed Feb 21, 2018

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petrochenkov 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-review Status: Awaiting review from the assignee but also interested parties. labels Feb 21, 2018

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Feb 25, 2018

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 27, 2018

estebank added 4 commits February 27, 2018 10:45

Detect missing if blocks

ba7039c

When unnecessarily using a fat arrow after an if condition, suggest the removal of it. When finding an if statement with no block, point at the `if` keyword to provide more context.

Add label to primary span in some parse errors

36baa81

Diagnostic tweaks (review)

d63d363

estebank force-pushed the match-missing-comma branch from 3e730aa to d63d363 Compare February 27, 2018 18:48

bors added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Mar 1, 2018

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Mar 1, 2018

Manishearth mentioned this pull request Mar 2, 2018

Rollup of 9 pull requests #48652

Merged

Manishearth closed this Mar 2, 2018

Manishearth reopened this Mar 2, 2018

bors added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Mar 2, 2018

petrochenkov closed this Mar 2, 2018

petrochenkov reopened this Mar 2, 2018

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Mar 2, 2018

Manishearth added a commit to Manishearth/rust that referenced this pull request Mar 2, 2018

Rollup merge of rust-lang#48338 - estebank:match-missing-comma, r=pet…

9d2f1e5

…rochenkov Fixes rust-lang#47311. r? @nrc

Manishearth added a commit to Manishearth/rust that referenced this pull request Mar 3, 2018

Rollup merge of rust-lang#48338 - estebank:match-missing-comma, r=pet…

23bfa23

…rochenkov Fixes rust-lang#47311. r? @nrc

Manishearth added a commit to Manishearth/rust that referenced this pull request Mar 3, 2018

Rollup merge of rust-lang#48338 - estebank:match-missing-comma, r=pet…

8c7c8fb

…rochenkov Fixes rust-lang#47311. r? @nrc

bors merged commit 24be75d into rust-lang:master Mar 3, 2018

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Provide context for missing comma in match arm and if statement without block #48338

Provide context for missing comma in match arm and if statement without block #48338

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Provide context for missing comma in match arm and if statement without block #48338

Provide context for missing comma in match arm and if statement without block #48338

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