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//! Proc Macro Expander stub
use crate::db::AstDatabase;
use base_db::{CrateId, ProcMacroId};
#[derive(Debug, Clone, Copy, Eq, PartialEq, Hash)]
pub struct ProcMacroExpander {
krate: CrateId,
proc_macro_id: Option<ProcMacroId>,
}
macro_rules! err {
($fmt:literal, $($tt:tt),*) => {
mbe::ExpandError::ProcMacroError(tt::ExpansionError::Unknown(format!($fmt, $($tt),*)))
};
($fmt:literal) => {
mbe::ExpandError::ProcMacroError(tt::ExpansionError::Unknown($fmt.to_string()))
}
}
impl ProcMacroExpander {
pub fn new(krate: CrateId, proc_macro_id: ProcMacroId) -> Self {
Self { krate, proc_macro_id: Some(proc_macro_id) }
}
pub fn dummy(krate: CrateId) -> Self {
// FIXME: Should store the name for better errors
Self { krate, proc_macro_id: None }
}
pub fn is_dummy(&self) -> bool {
self.proc_macro_id.is_none()
}
pub fn expand(
self,
db: &dyn AstDatabase,
calling_crate: CrateId,
tt: &tt::Subtree,
attr_arg: Option<&tt::Subtree>,
) -> Result<tt::Subtree, mbe::ExpandError> {
match self.proc_macro_id {
Some(id) => {
let krate_graph = db.crate_graph();
let proc_macro = krate_graph[self.krate]
.proc_macro
.get(id.0 as usize)
.ok_or_else(|| err!("No derive macro found."))?;
// Proc macros have access to the environment variables of the invoking crate.
let env = &krate_graph[calling_crate].env;
proc_macro.expander.expand(tt, attr_arg, env).map_err(mbe::ExpandError::from)
}
None => Err(mbe::ExpandError::UnresolvedProcMacro),
}
}
}
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