Add ast-grep custom-language wiring for .hew#2147
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ast-grep does not parse .hew natively. Register Hew as a custom language so
structural search and rewrite work across the codebase:
- sgconfig.yml registers the `hew` language, backed by a compiled copy of the
tree-sitter-hew grammar at .ast-grep/hew-lang.so (relative path; ast-grep
auto-discovers the config from anywhere in the tree).
- scripts/build-ast-grep-lang.sh compiles that grammar into the git-ignored
library; run it once after cloning, or after the grammar changes.
Example:
ast-grep run --lang hew --pattern 'fn $NAME($$$) -> $RET { $$$ }' std/
Structural lint rules run by `ast-grep scan` (wired via sgconfig.yml ruleDirs),
each validated against the current tree (see per-domain _REPORT.md):
- Rust fail-closed (error): `.ok()?` in the lowering pipeline and `Ty::Var`
constructed after inference (CLAUDE.md §2/§3).
- Rust panic/NYI (warning): bare `unreachable!()`, `todo!`/`unimplemented!`,
empty `.expect("")`.
- Rust concurrency/drop (advisory): poisoned-lock unwraps, and `mem::forget`/
`Box::leak` escapes to audit for drop-safety (CLAUDE.md §1/§9).
- Hew (.hew): redundant constructs — `len() == 0` -> `is_empty()`, a boolean
`match` -> `is_some()`, `== ""` -> `is_empty()`, no-op `clone` of a literal.
scripts/ast-grep-lint.sh runs the set and fails only on error-severity findings.
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Summary
Wire ast-grep to parse
.hewvia the tree-sitter-hew grammar, so structural search and rewrite work in this repo.sgconfig.ymlregistershewas a custom language (relativelibraryPath,expandoChar: _); ast-grep auto-discovers it from anywhere in the tree.scripts/build-ast-grep-lang.shcompiles the grammar into.ast-grep/hew-lang.sofrom a siblingtree-sitter-hewcheckout (or$TREE_SITTER_HEW_DIR).The compiled library is platform-specific and git-ignored (existing
*.sorule); contributors run the build script once after cloning.Verification
scripts/build-ast-grep-lang.shbuilds the library, thenast-grep run --lang hew -p 'fn $NAME($$$) { $$$ }' std/matches across the standard library.git statusshows only these two files; the.sostays ignored.Notes
Item-level patterns (
fn,impl,supervisor, …) work directly. Expression-level patterns use ast-grep'scontext+selector, since a bare top-level expression isn't valid Hew.Out of scope
The grammar itself lives in the tree-sitter-hew repository; this only adds the ast-grep integration.