Rollup merge of rust-lang#89956 - JohnTitor:suggest-case-insensitive-match-names, r=estebank

Suggest a case insensitive match name regardless of levenshtein distance

Fixes rust-lang#86170

Currently, `find_best_match_for_name` only returns a case insensitive match name depending on a Levenshtein distance. It's a bit unfortunate that that hides some suggestions for typos like `Bar` -> `BAR`. That idea is from rust-lang#46347 (comment), but I think it still makes some sense to show a candidate when we find a case insensitive match name as it's more like a typo.
Skipped the `candidate != lookup` check because the current (i.e, `levenshtein_match`) returns the exact same `Symbol` anyway but it doesn't seem to confuse anything on UI tests.

r? ``@estebank``

Author: matthiaskrgr

compiler/rustc_span/src/lev_distance.rs

@@ -58,34 +58,28 @@ pub fn find_best_match_for_name(
     let lookup = &lookup.as_str();
     let max_dist = dist.unwrap_or_else(|| cmp::max(lookup.len(), 3) / 3);
 
-    let (case_insensitive_match, levenshtein_match) = name_vec
+    // Priority of matches:
+    // 1. Exact case insensitive match
+    // 2. Levenshtein distance match
+    // 3. Sorted word match
+    if let Some(case_insensitive_match) =
+        name_vec.iter().find(|candidate| candidate.as_str().to_uppercase() == lookup.to_uppercase())
+    {
+        return Some(*case_insensitive_match);
+    }
+    let levenshtein_match = name_vec
         .iter()
         .filter_map(|&name| {
             let dist = lev_distance(lookup, &name.as_str());
             if dist <= max_dist { Some((name, dist)) } else { None }
         })
         // Here we are collecting the next structure:
-        // (case_insensitive_match, (levenshtein_match, levenshtein_distance))
-        .fold((None, None), |result, (candidate, dist)| {
-            (
-                if candidate.as_str().to_uppercase() == lookup.to_uppercase() {
-                    Some(candidate)
-                } else {
-                    result.0
-                },
-                match result.1 {
-                    None => Some((candidate, dist)),
-                    Some((c, d)) => Some(if dist < d { (candidate, dist) } else { (c, d) }),
-                },
-            )
+        // (levenshtein_match, levenshtein_distance)
+        .fold(None, |result, (candidate, dist)| match result {
+            None => Some((candidate, dist)),
+            Some((c, d)) => Some(if dist < d { (candidate, dist) } else { (c, d) }),
         });
-    // Priority of matches:
-    // 1. Exact case insensitive match
-    // 2. Levenshtein distance match
-    // 3. Sorted word match
-    if let Some(candidate) = case_insensitive_match {
-        Some(candidate)
-    } else if levenshtein_match.is_some() {
+    if levenshtein_match.is_some() {
         levenshtein_match.map(|(candidate, _)| candidate)
     } else {
         find_match_by_sorted_words(name_vec, lookup)

compiler/rustc_span/src/lev_distance/tests.rs

@@ -31,16 +31,12 @@ fn test_find_best_match_for_name() {
 
         assert_eq!(find_best_match_for_name(&input, Symbol::intern("1111111111"), None), None);
 
-        let input = vec![Symbol::intern("aAAA")];
+        let input = vec![Symbol::intern("AAAA")];
         assert_eq!(
-            find_best_match_for_name(&input, Symbol::intern("AAAA"), None),
-            Some(Symbol::intern("aAAA"))
+            find_best_match_for_name(&input, Symbol::intern("aaaa"), None),
+            Some(Symbol::intern("AAAA"))
         );
 
-        let input = vec![Symbol::intern("AAAA")];
-        // Returns None because `lev_distance > max_dist / 3`
-        assert_eq!(find_best_match_for_name(&input, Symbol::intern("aaaa"), None), None);
-
         let input = vec![Symbol::intern("AAAA")];
         assert_eq!(
             find_best_match_for_name(&input, Symbol::intern("aaaa"), Some(4)),

src/test/ui/hygiene/rustc-macro-transparency.stderr

@@ -2,29 +2,43 @@ error[E0425]: cannot find value `Opaque` in this scope
   --> $DIR/rustc-macro-transparency.rs:26:5
    |
 LL |     Opaque;
-   |     ^^^^^^ help: a local variable with a similar name exists (notice the capitalization): `opaque`
+   |     ^^^^^^ not found in this scope
 
 error[E0423]: expected value, found macro `semitransparent`
   --> $DIR/rustc-macro-transparency.rs:29:5
    |
+LL |     struct SemiTransparent;
+   |     ----------------------- similarly named unit struct `SemiTransparent` defined here
+...
 LL |     semitransparent;
    |     ^^^^^^^^^^^^^^^ not a value
    |
 help: use `!` to invoke the macro
    |
 LL |     semitransparent!;
    |                    +
+help: a unit struct with a similar name exists
+   |
+LL |     SemiTransparent;
+   |     ~~~~~~~~~~~~~~~
 
 error[E0423]: expected value, found macro `opaque`
   --> $DIR/rustc-macro-transparency.rs:30:5
    |
+LL |     struct Opaque;
+   |     -------------- similarly named unit struct `Opaque` defined here
+...
 LL |     opaque;
    |     ^^^^^^ not a value
    |
 help: use `!` to invoke the macro
    |
 LL |     opaque!;
    |           +
+help: a unit struct with a similar name exists
+   |
+LL |     Opaque;
+   |     ~~~~~~
 
 error: aborting due to 3 previous errors
 

src/test/ui/issues/issue-22933-2.stderr

@@ -5,7 +5,10 @@ LL | enum Delicious {
    | -------------- variant or associated item `PIE` not found here
 ...
 LL |     ApplePie = Delicious::Apple as isize | Delicious::PIE as isize,
-   |                                                       ^^^ variant or associated item not found in `Delicious`
+   |                                                       ^^^
+   |                                                       |
+   |                                                       variant or associated item not found in `Delicious`
+   |                                                       help: there is a variant with a similar name: `Pie`
 
 error: aborting due to previous error