[SR-6572] Specialize ExtensionDeclSyntax in libSyntax Parsing

[nkcsgexi]

Previous ID	SR-6572
Radar	None
Original Reporter	@nkcsgexi
Type	Task
Status	Resolved
Resolution	Done

Additional Detail from JIRA

Votes	0
Component/s	Source Tooling
Labels	Task
Assignee	sigito (JIRA)
Priority	Medium

md5: 0c91fdc7ba3ed9ea78b10c4bea2ed8fd

Issue Description:

Currently, libSyntax parsing doesn't specialize extension declarations, meaning all extension declarations are manifested as UnkownDecl. Since libSyntax clients will very likely interested in specialized analysis on extensions. We need to teach the parser to specialize them.

To demo what we have now:

$cat ~/Desktop/test.swift
extension C{}
func foo() {}
$../build/Ninja-DebugAssert/swift-macosx-x86_64/bin/swift-syntax-test -input-source-filename ~/Desktop/test.swift -parse-gen -print-node-kind -print-trivial-node-kind
<SourceFile><DeclList><TopLevelCodeDecl><StmtList><DeclarationStmt><UnknownDecl>extension <SimpleTypeIdentifier>C</SimpleTypeIdentifier>{<DeclList></DeclList>}</UnknownDecl></DeclarationStmt><DeclarationStmt><FunctionDecl>
func foo<FunctionSignature>(<FunctionParameterList></FunctionParameterList>) </FunctionSignature><CodeBlock>{<StmtList></StmtList>}</CodeBlock></FunctionDecl></DeclarationStmt></StmtList></TopLevelCodeDecl></DeclList>
</SourceFile>

See that the function decl is specialized however the extension decl is not. The desirable feature will be having extension decls specialized as well. One can follow the patch we specialized struct declaration from: c4604d7

[swift-ci]

Comment by Yura Samsoniuk (JIRA)

I have noticed some differences in what libSyntax emits for structs and extensions:

1. struct name is not parsed as a type, while extension has a defined type node (same is for a function, shouldn't foo in the example be part of the signature?);

2. struct member list is additionally wrapped in MemberDeclList which includes braces + DeclList, while in extension braces are consumed as independent tokens.

Are these differences intentional? Should they be addressed as a part of this bug?

[swift-ci]

Comment by Yura Samsoniuk (JIRA)

Done in #13632