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Parser: accept exprs like `$$0++--`.

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#67 2 comments 0 reactions 0 assignees View on GitHub

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Assessment

Difficulty
3/5
Estimated time
1-2 days
Newbie friendliness
62/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Quiet
Tech stack
rust
Domain
compilers

Research direction

Start by locating the Rust parser entry points that handle prefix $ and postfix ++/--, then compare their behavior with the already accepted $($0++)-- form. Add regression coverage for $$0++-- and verify that it parses successfully while preserving existing precedence behavior; keep the parser change easy to revert.

Written by the indexing model from the issue text.

Description

GNU bug

Title. Isomorphic expressions also fail to parse. These should parse the same way we currently accept $($0++)--. This is a bug because GNU AWK does accept them, but very amusingly, their docs give it as an example of an incorrect expression:

Also, operators cannot be combined in a way that violates the precedence rules; for example, $$0++-- is not a valid expression because the first $ has higher precedence than the ++; to avoid the problem the expression can be rewritten as $($0++)--.

Thus, and if possible, I would like the patch to be easily revertible.

Dominant language
Rust
Stars
27
Forks
7
Avg merge
4h 32m
Merged PRs (30d)
11

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