Spell checking identifiers

Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.invalid>
Wed, 24 Jun 2020 01:38:11 +0800

          From comp.compilers

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From: Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.invalid>
Newsgroups: comp.compilers
Date: Wed, 24 Jun 2020 01:38:11 +0800
Organization: Easynews - www.easynews.com
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Keywords: lex, errors, question, comment
Posted-Date: 23 Jun 2020 14:40:37 EDT
Content-Language: en-GB

Dear c.compilers,

While experimenting with Rust, I came across this suggestion.

    --> foo.rs:5:9
5 | return j; // the variable, not the type.
      | ^ help: a local variable with a similar name exists: `i`

Here it is suggesting i where I typed j. This is the same problem as
spell checking identifiers with fuzzy matching, so apologies for a po-
tentially misleading subject.

So, without going through the source of rustc to find out, I'm curious
about what general techniques people use to make this work? In particu-
lar the Damerau–Levenshtein distance algorithm is not appropriate for
dictionary lookups, as far as I know.

I've come across a survey of fuzzy matching algorithms, some of which
work with dictionaries but I have no idea which data structures would
be appropriate in a compiler, nor do I know what criteria I'd use to
choose an appropriate algorithm from such a survey.

As an added bonus, the same technique can of course be used to spell
check identifiers against a natural language dictionary. But since
such a dictionary is more static than the list of identifiers in the
current source file, a precomputed database will work, and a more
expensive indexing method can be used. Is there an indexing method
that works for this, but would not be appropriate for fuzzy matching
against identifiers?

[Apologies for not responding to my other topic yet, I should be able
to reply soon.]

Johann | email: invalid -> com | www.myrkraverk.com/blog/
I'm not from the Internet, I just work there. | twitter: @myrkraverk
[There's a vast amount of work on edit distance. My guess is they
use something like Levenshtein, but rather than use a constant
distance of 1 between different letters, the distance varies depending
on how different the letters look. -John]

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