rust-lang / rust-lang/rfcs

`match for` syntax to simplify matching across a for loop

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Description

I'm offering a simple suggestion for improving the readability of Rust code. If you think it's a bad idea, feel free to close the issue. I've noticed a pattern throughout my experience of writing code in Rust that could be better written with a simpler syntax, match for. The current syntax for writing a match for loop is as follows:

for token in pattern {
    match token {
        // matching code
    }
}

However, I am suggesting that it might be a good idea to also implement the following which will serve as syntactic sugar for the above and will eliminate the redundancy:

match for token in pattern {
    // matching code
}

As an example in some real world code, I currently have the following:

for pattern in self.template.clone() {
    match pattern {
        TemplateToken::Character(value) => filename.push(value),
        TemplateToken::Series  => if !self.no_name { filename.push_str(self.series_name.clone().as_str()); },
        TemplateToken::Season  => filename.push_str(self.season_number.to_string().as_str()),
        TemplateToken::Episode => filename.push_str(episode.to_padded_string('0', self.pad_length).as_str()),
        TemplateToken::Title   => if self.tvdb { filename.push_str(title); }
    }
}

However, it could be better written as the following simplified form:

match for pattern in self.template.clone() {
    TemplateToken::Character(value) => filename.push(value),
    TemplateToken::Series  => if !self.no_name { filename.push_str(self.series_name.clone().as_str()); },
    TemplateToken::Season  => filename.push_str(self.season_number.to_string().as_str()),
    TemplateToken::Episode => filename.push_str(episode.to_padded_string('0', self.pad_length).as_str()),
    TemplateToken::Title   => if self.tvdb { filename.push_str(title); }
}

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by reviewing the proposed match for examples and compare them with the existing for-then-match form. Determine whether the suggested syntax fits Rust's language design and RFC process; done means reaching a documented decision on the proposal.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
compilers
Issue type
Feature
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Clearly specified
Newbie friendliness
25/100

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