crates/hir_expand/src/builtin_attr_macro.rs

   1 //! Builtin attributes.
   2
   3 use mbe::ExpandResult;
   4 use syntax::ast;
   5
   6 use crate::{db::AstDatabase, name, AstId, CrateId, MacroCallId, MacroDefId, MacroDefKind};
   7
   8 macro_rules! register_builtin {
   9     ( $(($name:ident, $variant:ident) => $expand:ident),* ) => {
  10         #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
  11         pub enum BuiltinAttrExpander {
  12             $($variant),*
  13         }
  14
  15         impl BuiltinAttrExpander {
  16             pub fn expand(
  17                 &self,
  18                 db: &dyn AstDatabase,
  19                 id: MacroCallId,
  20                 tt: &tt::Subtree,
  21             ) -> ExpandResult<tt::Subtree> {
  22                 let expander = match *self {
  23                     $( BuiltinAttrExpander::$variant => $expand, )*
  24                 };
  25                 expander(db, id, tt)
  26             }
  27
  28             fn find_by_name(name: &name::Name) -> Option<Self> {
  29                 match name {
  30                     $( id if id == &name::name![$name] => Some(BuiltinAttrExpander::$variant), )*
  31                      _ => None,
  32                 }
  33             }
  34         }
  35
  36     };
  37 }
  38
  39 register_builtin! {
  40     (bench, Bench) => dummy_attr_expand,
  41     (cfg_accessible, CfgAccessible) => dummy_attr_expand,
  42     (cfg_eval, CfgEval) => dummy_attr_expand,
  43     (derive, Derive) => dummy_attr_expand,
  44     (global_allocator, GlobalAllocator) => dummy_attr_expand,
  45     (test, Test) => dummy_attr_expand,
  46     (test_case, TestCase) => dummy_attr_expand
  47 }
  48
  49 pub fn find_builtin_attr(
  50     ident: &name::Name,
  51     krate: CrateId,
  52     ast_id: AstId<ast::Macro>,
  53 ) -> Option<MacroDefId> {
  54     let expander = BuiltinAttrExpander::find_by_name(ident)?;
  55     Some(MacroDefId {
  56         krate,
  57         kind: MacroDefKind::BuiltInAttr(expander, ast_id),
  58         local_inner: false,
  59     })
  60 }
  61
  62 fn dummy_attr_expand(
  63     _db: &dyn AstDatabase,
  64     _id: MacroCallId,
  65     tt: &tt::Subtree,
  66 ) -> ExpandResult<tt::Subtree> {
  67     ExpandResult::ok(tt.clone())
  68 }