[code-reflection] RFR: JavaRef extends TypeElement

[Maurizio Cimadamore]

On Tue, 29 Apr 2025 22:12:34 GMT, Paul Sandoz <psandoz at openjdk.org> wrote:

> Each implementation of `JavaRef` supports an external form, using the sigil prefix `&` to indicate a reference of some kind.
> 
> The externalized form of `TypeVarRef` is changed to be uniformly structured. This required update to the code model text of a few tests. Arguably we are taking a step back in terms of readability, but we can address that later - it was easier to update a few tests rather than preserve the existing encoding in a few places.
> 
> We still rely on the bespoke string form for java refs, which is used as the value of an externalized attribute. Ideally such attribute values are either instances of `JavaRef` or `ExternalizedTypeElement` to be transformed into the appropriate `JavaRef`. We can address that later to further separate out parsing.
> 
> I believe we have what we need to further enhance the code model builder to not rely on bespoke parsing logic of types and refs. We can either construct `ExternalizedTypeElement` tree instances explicitly or parse from a very simple grammar. If we are careful i believe we can share the results of nested type elements if reused e.g. as in `List<Double>` and `Set<Double>`.
> 
> More generally it now means we can generate a simple s-expression-like tree for the whole code model, e.g., a string where the `(` and `)` characters represent tree structure and say `L` represents a leaf node, and a list of leaf node values in topological order.
> 
> --
> 
> Below is the type grammar, which i believe is consistent with what we have implemented.
> 
> # Type element grammar
> 
> ## General structure
> 
> 
> identifier
>   string
> 
> name
>   identifier
> 
> sigil
>   # | . | & | + | - | [
> 
> type
>   sigil
>   identifier
>   sigil identifier
>   identifier < types >
>   sigil identifier < types >
> 
> types
>    type
>    type , types
> 
> 
> ## Core types
> 
> 
> varType
>   "var" < type >
> 
> tupleType
>   "tuple"
>   "tuple" < types >
> 
> funcType
>   "func" < types >
> 
> 
> # Java types
> 
> 
> javaType
>   primitiveType | classType | wildCardType | arrayType | typeVariableType
> 
> javaType-no-wildCardType
>   primitiveType | classType | arrayType | typeVariableType
> 
> primitiveType
>   boolean | byte | ... | void
> 
> classType
>   name
>   name < paramTypes >
>   . < enclosingType , innerType >
> paramTypes
>   javaType
>   javaType , javaTypes
> enclosingType
>   classType
> innerType
>   classType
> 
> wildcardType
>   + < wildcardTypeBound >
>   - < wildcardTypeBound >
> wildcardTypeBound
>   javaType-no-wildCardType
> 
> arrayType
>   dims < javaType >
> dims
>  [
>  [ dims
> 
> typeVariableType
>   "#" name < typeVariableTypeOwner , typeVariableTypeBound >
> typeVa...

src/jdk.incubator.code/share/classes/jdk/incubator/code/type/ConstructorRef.java line 47:

> 45:     FunctionType type();
> 46: 
> 47:     default TypeElement refType() {

I don't get this default method -- the concrete impl overrides it.

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PR Review Comment: https://git.openjdk.org/babylon/pull/416#discussion_r2068183388