Rollup merge of #108200 - jhpratt:restricted-damerau-levenshtein-distance, r=tmiasko

Use restricted Damerau-Levenshtein distance for diagnostics

This replaces the existing Levenshtein algorithm with the Damerau-Levenshtein algorithm. This means that "ab" to "ba" is one change (a transposition) instead of two (a deletion and insertion). More specifically, this is a _restricted_ implementation, in that "ca" to "abc" cannot be performed as "ca" → "ac" → "abc", as there is an insertion in the middle of a transposition. I believe that errors like that are sufficiently rare that it's not worth taking into account.

This was first brought up [on IRLO](https://internals.rust-lang.org/t/18227) when it was noticed that the diagnostic for `prinltn!` (transposed L and T) was `print!` and not `println!`. Only a single existing UI test was effected, with the result being an objective improvement.

~~I have left the method name and various other references to the Levenshtein algorithm untouched, as the exact manner in which the edit distance is calculated should not be relevant to the caller.~~

r? ``@estebank``

``@rustbot`` label +A-diagnostics +C-enhancement
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Matthias Krüger 2023-02-20 14:32:55 +01:00 committed by GitHub
commit 226ce31edd
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21 changed files with 357 additions and 271 deletions

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@ -37,8 +37,8 @@ use rustc_middle::ty::DynKind;
use rustc_middle::ty::GenericParamDefKind;
use rustc_middle::ty::{self, Const, DefIdTree, IsSuggestable, Ty, TyCtxt, TypeVisitable};
use rustc_session::lint::builtin::{AMBIGUOUS_ASSOCIATED_ITEMS, BARE_TRAIT_OBJECTS};
use rustc_span::edit_distance::find_best_match_for_name;
use rustc_span::edition::Edition;
use rustc_span::lev_distance::find_best_match_for_name;
use rustc_span::symbol::{kw, Ident, Symbol};
use rustc_span::{sym, Span, DUMMY_SP};
use rustc_target::spec::abi;