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unified: Swift grammar cleanup part 1 - #21821
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7c91dd9CompareThe astute reader will note that we seem to _lose_ some node types in the process. Apparently, these were unreachable in the grammar, and the newer version of tree-sitter removes such "dead code".
This caused any field containing an _expression to appear as if it could countain any number of such nodes. It also threw away the information that there was a `?` marker there. To fix it, we simply move the definition into its own named node.
We make _referenceable_operator a named node. This prevents it from bleeding through to the _expression definition. It likely also makes the output easier to deal with, as bare operators used as arguments now have a named node wrapping them in the AST. Also removes a duplicated inclusion of _comparison_operator that served no purpose.
Before, the `condition` field of an if statement supposedly could contain things like parentheses and commas, due to bleeding from referenced anonymous nodes. Making the node named makes this issue go away.
Supertypes are a honking great idea. We should use more of them. This massively cleans up the node types, without polluting the AST with `expression` nodes.
Gets rid of a bunch of ad-hoc node type unions.
You know the drill. We just make an anonymous node named instead. In this case, however, we have to be a bit more clever about how to rewrite it. We turn the sequence of a type followed by an optional ! into a _choice_ between mere type or type followed by bang (the latter being our new named node).
Adds a new type `nested_type_identifier`, which contains the choice-branch that previously allowed those tokens to bleed through into the closest parent field.
Because `_type` was anonymous, its body was inlined in all of the places it appeared. Because this body contained a `name` field, this field was _also_ inlined. This caused a bunch of nodes to have spurious `name` fields, and for some of them (that already had such a field) it caused that field have multiplicity greater than one. To fix this, we make the `_type` node named, which prevents the errant field from escaping.
Same pattern we've seen many times before: a field on an anonymous node gets attached to the parent node instead. I'm not 100% sure this is the right solution, but it seemed wrong to just make `_parenthesized_type` named instead (we don't usually name parentheticals). At the very least, this cleans up the spurious navigation_expression.element and tuple_type_item.element fields.
Same procedure as before -- we change the anonymous node to a named node, and the problem magically goes away.
Hides a bunch of huge unions under (hopefully) sensible supertypes.
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May 12, 2026 13:17
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Pull request overview
This PR continues the unified Swift grammar cleanup by introducing explicit supertypes and normalizing several grammar rules (types, expressions, conditions), then updating the unified Swift dbscheme and QL AST library to match the regenerated tree-sitter schema. It also adds tooling and documentation to make future grammar edits easier to regenerate and review.
Changes:
- Add
unified/scripts/regenerate-grammar.shand document the Swift grammar regeneration workflow inunified/AGENTS.md. - Refactor
unified/extractor/tree-sitter-swift/grammar.jsto introduce supertypes and make key constructs (e.g.expression,type,if_condition) first-class named rules. - Regenerate/adjust Swift schema surfaces:
unified/ql/lib/unified.dbscheme,unified/ql/lib/codeql/unified/Ast.qll, and addunified/extractor/tree-sitter-swift/node-types.yml.
Show a summary per file
| File | Description |
|---|---|
| unified/scripts/regenerate-grammar.sh | Adds a one-shot script to regenerate tree-sitter outputs and refresh node-types.yml. |
| unified/ql/lib/unified.dbscheme | Updates Swift dbscheme to reflect the new/cleaned grammar structure (including new supertypes and field normalization). |
| unified/ql/lib/codeql/unified/Ast.qll | Aligns the Swift AST QL wrappers with the updated Swift dbscheme/schema. |
| unified/extractor/tree-sitter-swift/node-types.yml | Adds a human-readable node-types view for reviewing grammar changes. |
| unified/extractor/tree-sitter-swift/grammar.js | Introduces supertypes and refactors rules to reduce ambiguity and standardize node shapes. |
| unified/AGENTS.md | Documents how to regenerate and review Swift grammar changes. |
Copilot's findings
- Files reviewed: 5/6 changed files
- Comments generated: 1
| - ">" | ||
| - ">=" | ||
| - ">>" | ||
| - "?" |
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A lot of commits, but most of the churn is just files being regenerated. This only happens in separate commits, so those commits do not need to be reviewed.