This change introduces experimental AST support for the "declaring
constructors" (DeCo) feature and wires the parser to build explicit
nodes for primary constructors. The new behavior is gated by a static
switch:
analyzer/dart/ast/ast.dart: useDeclaringConstructorsAst (experimental)
When the flag is **true** (must be set once before parsing and not
changed thereafter):
* Declarations expose structured bodies:
- `ClassDeclaration.body` / `MixinDeclaration.body`
- `EnumDeclaration.body`
- `ExtensionDeclaration.body`
- `ExtensionTypeDeclaration.body`
Legacy bracket/members tokens (`leftBracket`, `members`,
`rightBracket`) throw `UnsupportedError`.
* The declaration "name" area is modeled as `namePart: ClassNamePart`,
which is either:
- `NameWithTypeParameters` (e.g., `A<T>`), or
- `PrimaryConstructorDeclaration` (e.g., `A<T>.named(...)`).
Legacy fields (`name`, `typeParameters`) throw `UnsupportedError`.
For extension types, `representation` also throws under the flag and
is represented via `PrimaryConstructorDeclaration`.
* Child iteration (`childEntities`), visiting (`visitChildren`), and
token boundaries (`endToken`) adapt to the new shape.
Parser changes:
* Build `PrimaryConstructorDeclaration` / `PrimaryConstructorName` via a
new `_PrimaryConstructorBuilder`. For extension types, the existing
representation syntax is mapped to a primary constructor when the flag
is enabled.
* Add `NullValue.PrimaryConstructor` to the stack listener to carry the
parsed primary constructor through the builder pipeline.
Implementation details:
* Introduce small internal *Stub classes (e.g., `ClassBodyImplStub`,
`EnumBodyImplStub`, `RepresentationDeclarationImplStub`) to satisfy
constructor requirements for fields that are not surfaced under the
current mode, avoiding API churn while the feature is gated.
* Update API surface to make `body` and `namePart` available on the
affected declarations and document which legacy getters throw when the
flag is enabled.
Rationale:
This lays the AST groundwork for DeCo while preserving backwards
compatibility by default. Consumers can opt in to validate workflows and
migrate incrementally.
Bug: https://github.com/dart-lang/sdk/issues/61701
Change-Id: Ie5300b2958383bf3b2e9d6faf138bb7f74c9d7ed
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/455820
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>
Reviewed-by: Paul Berry <paulberry@google.com>
Konstantin Shcheglov
7ef361bda0