Fix incorrect span when using byte-escaped rbrace #103828

cassaundra · 2022-11-01T02:04:34Z

Fix #103826, a format args span issue introduced in #102214.

The current solution for tracking skipped characters made it so that certain situations were ambiguous enough that the original span couldn't be worked out later. This PR improves on the original solution by keeping track of groups of skipped characters using a map, and fixes the previous bug. See an example of this ambiguity in the previous PR's discussion.

rustbot · 2022-11-01T02:04:42Z

r? @oli-obk

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cassaundra · 2022-11-01T02:09:54Z

compiler/rustc_parse_format/src/lib.rs

-                        // consume `\xAB` literal
-                        if let Some((pos, _)) = s.next() {
-                            skips.push(pos);
-                        } else {
-                            break;
-                        }


Note: a small check removed here. The lexer will raise "numeric character escape is too short" before we ever get to this code if there aren't three characters following the \.

oli-obk · 2022-11-08T10:49:17Z

r? @cjgillot since you also reviewed #102214

bors · 2022-11-08T10:56:08Z

☔ The latest upstream changes (presumably #104138) made this pull request unmergeable. Please resolve the merge conflicts.

cjgillot · 2022-11-12T13:40:16Z

compiler/rustc_parse_format/src/lib.rs

    let snippet = match snippet {
        Some(ref s) if s.starts_with('"') || s.starts_with("r\"") || s.starts_with("r#") => s,
        _ => return (vec![], false),
    };

-    fn find_skips(snippet: &str, is_raw: bool) -> Vec<usize> {
+    fn find_width_map(snippet: &str, is_raw: bool) -> Vec<InnerWidthMapping> {


This will be changed by #104193.
cc @TaKO8Ki

Given that there are conflicts from both #103651 and #104193, I'll go ahead and resolve the other issues before I try sort those out.

cjgillot · 2022-11-12T13:41:29Z

compiler/rustc_parse_format/src/lib.rs

-    /// Characters that need to be shifted
-    skips: Vec<usize>,
+    /// Inner span width of characters that need to be shifted
+    width_map: Vec<InnerWidthMapping>,


Could you elaborate the comment? Notably: what is the index of the Vec?

cjgillot · 2022-11-12T13:41:43Z

compiler/rustc_parse_format/src/lib.rs

+pub struct InnerWidthMapping {
+    pub position: usize,
+    pub before: usize,
+    pub after: usize,


Could you comment the individual fields?
What are they: positions? Starting at which point of reference?

Added some comments.

For what it's worth, I think this could also be refactored to instead have a InnerSpan and a usize, which might make some of the intent more clear.

cjgillot · 2022-11-12T13:45:43Z

compiler/rustc_parse_format/src/lib.rs

@@ -224,7 +237,7 @@ impl<'a> Iterator for Parser<'a> {
                '{' => {
                    let curr_last_brace = self.last_opening_brace;
                    let byte_pos = self.to_span_index(pos);
-                    let lbrace_end = self.to_span_index(pos + 1);
+                    let lbrace_end = InnerOffset(byte_pos.0 + self.to_span_width(pos));


Could we wrap all creations of InnerOffset?

Hmm, not exactly sure what you mean.

Maybe related: a function that gives you both position and width could clean this up

cjgillot · 2022-11-12T13:48:56Z

compiler/rustc_parse_format/src/lib.rs

-                pos += 1;
-            } else if pos == *skip && raw == 0 {
-                pos += 1;
+    fn remap_pos(&self, mut pos: usize) -> usize {


Could you add a comment: what are the input and output usizes?
Should we introduce some type to differentiate "raw" from "remapped" positions?

Yes, that should be InnerOffset, my bad.

Fix rust-lang#103826.

cassaundra · 2022-11-22T04:37:40Z

Rebased against master.

cjgillot · 2022-12-26T10:14:21Z

Thanks @cassaundra. Sorry for the slow review.
@bors r+

bors · 2022-12-26T10:14:23Z

📌 Commit 35c7939 has been approved by cjgillot

It is now in the queue for this repository.

bors · 2022-12-26T12:03:50Z

⌛ Testing commit 35c7939 with merge 731e0bf...

bors · 2022-12-26T15:10:26Z

☀️ Test successful - checks-actions
Approved by: cjgillot
Pushing 731e0bf to master...

rust-timer · 2022-12-26T16:30:35Z

Finished benchmarking commit (731e0bf): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

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…cjgillot Fix incorrect span when using byte-escaped rbrace Fix rust-lang#103826, a format args span issue introduced in rust-lang#102214. The current solution for tracking skipped characters made it so that certain situations were ambiguous enough that the original span couldn't be worked out later. This PR improves on the original solution by keeping track of groups of skipped characters using a map, and fixes the previous bug. See an example of this ambiguity in the [previous PR's discussion](rust-lang#102214 (comment)).

rustbot assigned oli-obk Nov 1, 2022

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Nov 1, 2022

cassaundra commented Nov 1, 2022

View reviewed changes

rustbot assigned cjgillot and unassigned oli-obk Nov 8, 2022

cjgillot reviewed Nov 12, 2022

View reviewed changes

cassaundra force-pushed the fix-format-args-span2 branch from af0d14c to 4ccc7f3 Compare November 18, 2022 05:27

Fix incorrect span when using byte-escaped rbrace

35c7939

Fix rust-lang#103826.

cassaundra force-pushed the fix-format-args-span2 branch from 4ccc7f3 to 35c7939 Compare November 22, 2022 04:37

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 Dec 26, 2022

bors added the merged-by-bors This PR was explicitly merged by bors. label Dec 26, 2022

bors merged commit 731e0bf into rust-lang:master Dec 26, 2022

rustbot added this to the 1.68.0 milestone Dec 26, 2022

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Fix incorrect span when using byte-escaped rbrace #103828

Fix incorrect span when using byte-escaped rbrace #103828

cassaundra commented Nov 1, 2022 •

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Fix incorrect span when using byte-escaped rbrace #103828

Fix incorrect span when using byte-escaped rbrace #103828

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cassaundra commented Nov 22, 2022

cjgillot commented Dec 26, 2022

bors commented Dec 26, 2022

bors commented Dec 26, 2022

bors commented Dec 26, 2022

rust-timer commented Dec 26, 2022

Overall result: no relevant changes - no action needed

cassaundra commented Nov 1, 2022 •

edited

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