Rust: refactor pre_emit! and post_emit! to a trait

[redsun82]

This refactors the macro-based magic of pre_emit and post_emit to use a trait on Translator, with the corresponding ast node as generic parameter. This needs to be explicitly requested for an AST node in the ast-generator code (changing the has_special_emission function).

This is safer, less error-prone, and nicer to the IDE.

[Copilot]

Pull Request Overview

Refactors the existing macro-based pre_emit!/post_emit! logic into a trait-driven approach, improving IDE support and reducing hidden macro magic. Key changes include:

• Introduce HasTrapClass and Emission<T> traits in mappings.rs and implement them for all AST nodes in base.rs.
• Remove pre_emit!/post_emit! macros and update the ast-generator templates to emit self.pre_emit(node) and self.post_emit(node, label) calls.
• Extend the AST generator to emit HasTrapClass impls and guard template sections with a new has_special_emission flag.

Reviewed Changes

Copilot reviewed 7 out of 8 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
rust/extractor/src/translate/mappings.rs	Add HasTrapClass and Emission traits
rust/extractor/src/translate/base.rs	Remove macros, implement Emission<T> for AST nodes, add emit_else_branch
rust/ast-generator/templates/{pre_emission,post_emission}.mustache	Generate trait-based pre/post emission calls
rust/ast-generator/templates/trap_class_mapping.mustache	Emit HasTrapClass impls for nodes with special emission
rust/ast-generator/templates/extractor.mustache	Remove macro imports, update imports and include new template partials
rust/ast-generator/src/main.rs	Add has_special_emission helper and propagate flag

Comments suppressed due to low confidence (1)

rust/extractor/src/translate/mappings.rs:6

• [nitpick] Consider adding a doc comment to explain the purpose of the HasTrapClass trait and its associated TrapClass type for future maintainers.

pub(crate) trait HasTrapClass: AstNode {

[Copilot]

The import ast::RangeItem is unused in this file. Consider removing it to clean up unused dependencies.

Suggested change

	use ra_ap_syntax::{AstNode, ast, ast::RangeItem};
	use ra_ap_syntax::{AstNode, ast};