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|
/// Machinery for macro expansion.
///
/// One of the more complicated things about macros is managing the source code
/// that is produced after expansion. See `HirFileId` and `MacroCallId` for how
/// do we do that.
///
/// When the file-management question is resolved, all that is left is a
/// token-tree-to-token-tree transformation plus hygiene. We don't have either of
/// those yet, so all macros are string based at the moment!
use std::sync::Arc;
use ra_syntax::{
TextRange, TextUnit, SourceFile, AstNode, SyntaxNode, TreeArc, SyntaxNodePtr,
ast,
};
use crate::{MacroCallId, PersistentHirDatabase};
// Hard-coded defs for now :-(
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum MacroDef {
Vec,
}
impl MacroDef {
/// Expands macro call, returning the expansion and offset to be used to
/// convert ranges between expansion and original source.
pub fn ast_expand(macro_call: &ast::MacroCall) -> Option<(TextUnit, MacroExpansion)> {
let (def, input) = MacroDef::from_call(macro_call)?;
let exp = def.expand(input)?;
let off = macro_call.token_tree()?.syntax().range().start();
Some((off, exp))
}
fn from_call(macro_call: &ast::MacroCall) -> Option<(MacroDef, MacroInput)> {
let def = {
let path = macro_call.path()?;
let name_ref = path.segment()?.name_ref()?;
if name_ref.text() == "vec" {
MacroDef::Vec
} else {
return None;
}
};
let input = {
let arg = macro_call.token_tree()?.syntax();
MacroInput { text: arg.text().to_string() }
};
Some((def, input))
}
fn expand(self, input: MacroInput) -> Option<MacroExpansion> {
match self {
MacroDef::Vec => self.expand_vec(input),
}
}
fn expand_vec(self, input: MacroInput) -> Option<MacroExpansion> {
let text = format!(r"fn dummy() {{ {}; }}", input.text);
let file = SourceFile::parse(&text);
let array_expr = file.syntax().descendants().find_map(ast::ArrayExpr::cast)?;
let ptr = SyntaxNodePtr::new(array_expr.syntax());
let src_range = TextRange::offset_len(0.into(), TextUnit::of_str(&input.text));
let ranges_map = vec![(src_range, array_expr.syntax().range())];
let res = MacroExpansion { text, ranges_map, ptr };
Some(res)
}
}
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct MacroInput {
// Should be token trees
pub text: String,
}
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct MacroExpansion {
/// The result of macro expansion. Should be token tree as well.
text: String,
/// Correspondence between ranges in the original source code and ranges in
/// the macro.
ranges_map: Vec<(TextRange, TextRange)>,
/// Implementation detail: internally, a macro is expanded to the whole file,
/// even if it is an expression. This `ptr` selects the actual expansion from
/// the expanded file.
ptr: SyntaxNodePtr,
}
impl MacroExpansion {
// FIXME: does not really make sense, macro expansion is not necessary a
// whole file. See `MacroExpansion::ptr` as well.
pub(crate) fn file(&self) -> TreeArc<SourceFile> {
SourceFile::parse(&self.text)
}
pub fn syntax(&self) -> TreeArc<SyntaxNode> {
self.ptr.to_node(&self.file()).to_owned()
}
/// Maps range in the source code to the range in the expanded code.
pub fn map_range_forward(&self, src_range: TextRange) -> Option<TextRange> {
for (s_range, t_range) in self.ranges_map.iter() {
if src_range.is_subrange(&s_range) {
let src_at_zero_range = src_range - src_range.start();
let src_range_offset = src_range.start() - s_range.start();
let src_range = src_at_zero_range + src_range_offset + t_range.start();
return Some(src_range);
}
}
None
}
/// Maps range in the expanded code to the range in the source code.
pub fn map_range_back(&self, tgt_range: TextRange) -> Option<TextRange> {
for (s_range, t_range) in self.ranges_map.iter() {
if tgt_range.is_subrange(&t_range) {
let tgt_at_zero_range = tgt_range - tgt_range.start();
let tgt_range_offset = tgt_range.start() - t_range.start();
let src_range = tgt_at_zero_range + tgt_range_offset + s_range.start();
return Some(src_range);
}
}
None
}
}
pub(crate) fn expand_macro_invocation(
db: &impl PersistentHirDatabase,
invoc: MacroCallId,
) -> Option<Arc<MacroExpansion>> {
let loc = invoc.loc(db);
let syntax = db.file_item(loc.source_item_id);
let macro_call = ast::MacroCall::cast(&syntax).unwrap();
let (def, input) = MacroDef::from_call(macro_call)?;
def.expand(input).map(Arc::new)
}
|
