[Bug]: Swift: a local with same name as a modifier (prefix, open, final...) used in a switch case body gives a syntax-parse error from tree-sitter-swift

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Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
65/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
python, swift
Domain
developer-experience, tooling

Research direction

The issue names extract.py, the Swift test parametrization, and the changelog. Read the existing handling for modifier-named identifiers and run the two Swift test files mentioned in the issue. Done means the covered switch-case expressions parse, the six additional names are included, and those tests pass; the listed exceptions remain unchanged.

Written by the indexing model from the issue text.

Description

bug
Pre-flight checks
  • I have checked the Troubleshooting section in the README
What happened?

Summary:
tree-sitter-swift 0.7.4 cannot parse a local value whose name is a Swift contextual modifier when it is used as return name <operator> or return name.member inside a switch case. The grammar reads the identifier as a declaration modifier waiting for a declaration, and the surrounding code collapses into ERROR nodes. Graphify warns about a syntax-parse error at line: X and extracts the file only partially.

Related but distinct: #3540 (another tree-sitter-swift parse failure, if let x = await ...).

The trigger is a modifier-named identifier at the start of an expression statement inside a case body, followed by an operator or member access.

Limits and unfixed exceptions (the fix doesn't cover these, so behavior is unchanged: partial extraction plus the warning):

  1. A function parameter named like a modifier. Renaming it would change the argument label and every call site.
  2. A closure parameter, as in xs.map { prefix in ... }.
  3. Tuple destructuring, as in let (prefix, b) = t.
  4. A file with any other syntax error, because the rewrite is accepted only if the whole file then parses cleanly.
  5. Names I haven't tested. The list is only what I verified.

Covered: if let prefix = x, and a type-scope property with the same name.

Code change: added six names that also fail to extract.py, the test parametrization, and the changelog: distributed, nonmutating, public, private, internal and fileprivate.

Validation: The Swift tests pass, 36 of 36 in the two files I re-ran after the change. I did not re-run the full suite because it had 8 failures before this change, and they also fail without this fix.

static, class and inout also error, but they are reserved keywords, so let class = 1 isn't valid Swift.

Steps to reproduce

Minimal repro

let prefix = "x"
switch kind {
case 0:
return prefix + "a" // error

Case body Result
return prefix + "a" error
return prefix.count > 0 ? "a" : "b" error
return prefix ok
print(prefix) ok
let y = prefix ok
x = prefix + "a" ok
return "a" + prefix ok
return pfx + "a" (local renamed) ok
return prefix + "a" inside if k == 0 { ... } instead of a switch ok
return prefix + "a" after the switch, outside any case ok
Error output or graph output
codefile.swift had a syntax-parse error at line X, so its extraction may be partial (Y symbols found).
Graphify version

0.9.102

Operating System

macOS

Python Version

3.13

Installation Method

uv tool install (recommended)

Additional Environment Details

No response

Additional context

No response

Dominant language
Python
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Merged PRs (30d)
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