1 files changed, 360 insertions, 0 deletions

diff --git a/crates/hir_def/src/body.rs b/crates/hir_def/src/body.rs
new file mode 100644
index 000000000..9a9a605dd
--- /dev/null
+++ b/crates/hir_def/src/body.rs
@@ -0,0 +1,360 @@
+//! Defines `Body`: a lowered representation of bodies of functions, statics and
+//! consts.
+mod lower;
+pub mod scope;
+
+use std::{mem, ops::Index, sync::Arc};
+
+use arena::{map::ArenaMap, Arena};
+use base_db::CrateId;
+use cfg::CfgOptions;
+use drop_bomb::DropBomb;
+use either::Either;
+use hir_expand::{ast_id_map::AstIdMap, hygiene::Hygiene, AstId, HirFileId, InFile, MacroDefId};
+use rustc_hash::FxHashMap;
+use syntax::{ast, AstNode, AstPtr};
+use test_utils::mark;
+
+pub(crate) use lower::LowerCtx;
+
+use crate::{
+    attr::Attrs,
+    db::DefDatabase,
+    expr::{Expr, ExprId, Pat, PatId},
+    item_scope::BuiltinShadowMode,
+    item_scope::ItemScope,
+    nameres::CrateDefMap,
+    path::{ModPath, Path},
+    src::HasSource,
+    AsMacroCall, DefWithBodyId, HasModule, Lookup, ModuleId,
+};
+
+/// A subset of Expander that only deals with cfg attributes. We only need it to
+/// avoid cyclic queries in crate def map during enum processing.
+pub(crate) struct CfgExpander {
+    cfg_options: CfgOptions,
+    hygiene: Hygiene,
+}
+
+pub(crate) struct Expander {
+    cfg_expander: CfgExpander,
+    crate_def_map: Arc<CrateDefMap>,
+    current_file_id: HirFileId,
+    ast_id_map: Arc<AstIdMap>,
+    module: ModuleId,
+    recursion_limit: usize,
+}
+
+#[cfg(test)]
+const EXPANSION_RECURSION_LIMIT: usize = 32;
+
+#[cfg(not(test))]
+const EXPANSION_RECURSION_LIMIT: usize = 128;
+
+impl CfgExpander {
+    pub(crate) fn new(
+        db: &dyn DefDatabase,
+        current_file_id: HirFileId,
+        krate: CrateId,
+    ) -> CfgExpander {
+        let hygiene = Hygiene::new(db.upcast(), current_file_id);
+        let cfg_options = db.crate_graph()[krate].cfg_options.clone();
+        CfgExpander { cfg_options, hygiene }
+    }
+
+    pub(crate) fn parse_attrs(&self, owner: &dyn ast::AttrsOwner) -> Attrs {
+        Attrs::new(owner, &self.hygiene)
+    }
+
+    pub(crate) fn is_cfg_enabled(&self, owner: &dyn ast::AttrsOwner) -> bool {
+        let attrs = self.parse_attrs(owner);
+        attrs.is_cfg_enabled(&self.cfg_options)
+    }
+}
+
+impl Expander {
+    pub(crate) fn new(
+        db: &dyn DefDatabase,
+        current_file_id: HirFileId,
+        module: ModuleId,
+    ) -> Expander {
+        let cfg_expander = CfgExpander::new(db, current_file_id, module.krate);
+        let crate_def_map = db.crate_def_map(module.krate);
+        let ast_id_map = db.ast_id_map(current_file_id);
+        Expander {
+            cfg_expander,
+            crate_def_map,
+            current_file_id,
+            ast_id_map,
+            module,
+            recursion_limit: 0,
+        }
+    }
+
+    pub(crate) fn enter_expand<T: ast::AstNode>(
+        &mut self,
+        db: &dyn DefDatabase,
+        local_scope: Option<&ItemScope>,
+        macro_call: ast::MacroCall,
+    ) -> Option<(Mark, T)> {
+        self.recursion_limit += 1;
+        if self.recursion_limit > EXPANSION_RECURSION_LIMIT {
+            mark::hit!(your_stack_belongs_to_me);
+            return None;
+        }
+
+        let macro_call = InFile::new(self.current_file_id, &macro_call);
+
+        if let Some(call_id) = macro_call.as_call_id(db, self.crate_def_map.krate, |path| {
+            if let Some(local_scope) = local_scope {
+                if let Some(def) = path.as_ident().and_then(|n| local_scope.get_legacy_macro(n)) {
+                    return Some(def);
+                }
+            }
+            self.resolve_path_as_macro(db, &path)
+        }) {
+            let file_id = call_id.as_file();
+            if let Some(node) = db.parse_or_expand(file_id) {
+                if let Some(expr) = T::cast(node) {
+                    log::debug!("macro expansion {:#?}", expr.syntax());
+
+                    let mark = Mark {
+                        file_id: self.current_file_id,
+                        ast_id_map: mem::take(&mut self.ast_id_map),
+                        bomb: DropBomb::new("expansion mark dropped"),
+                    };
+                    self.cfg_expander.hygiene = Hygiene::new(db.upcast(), file_id);
+                    self.current_file_id = file_id;
+                    self.ast_id_map = db.ast_id_map(file_id);
+                    return Some((mark, expr));
+                }
+            }
+        }
+
+        // FIXME: Instead of just dropping the error from expansion
+        // report it
+        None
+    }
+
+    pub(crate) fn exit(&mut self, db: &dyn DefDatabase, mut mark: Mark) {
+        self.cfg_expander.hygiene = Hygiene::new(db.upcast(), mark.file_id);
+        self.current_file_id = mark.file_id;
+        self.ast_id_map = mem::take(&mut mark.ast_id_map);
+        self.recursion_limit -= 1;
+        mark.bomb.defuse();
+    }
+
+    pub(crate) fn to_source<T>(&self, value: T) -> InFile<T> {
+        InFile { file_id: self.current_file_id, value }
+    }
+
+    pub(crate) fn is_cfg_enabled(&self, owner: &dyn ast::AttrsOwner) -> bool {
+        self.cfg_expander.is_cfg_enabled(owner)
+    }
+
+    fn parse_path(&mut self, path: ast::Path) -> Option<Path> {
+        Path::from_src(path, &self.cfg_expander.hygiene)
+    }
+
+    fn resolve_path_as_macro(&self, db: &dyn DefDatabase, path: &ModPath) -> Option<MacroDefId> {
+        self.crate_def_map
+            .resolve_path(db, self.module.local_id, path, BuiltinShadowMode::Other)
+            .0
+            .take_macros()
+    }
+
+    fn ast_id<N: AstNode>(&self, item: &N) -> AstId<N> {
+        let file_local_id = self.ast_id_map.ast_id(item);
+        AstId::new(self.current_file_id, file_local_id)
+    }
+}
+
+pub(crate) struct Mark {
+    file_id: HirFileId,
+    ast_id_map: Arc<AstIdMap>,
+    bomb: DropBomb,
+}
+
+/// The body of an item (function, const etc.).
+#[derive(Debug, Eq, PartialEq)]
+pub struct Body {
+    pub exprs: Arena<Expr>,
+    pub pats: Arena<Pat>,
+    /// The patterns for the function's parameters. While the parameter types are
+    /// part of the function signature, the patterns are not (they don't change
+    /// the external type of the function).
+    ///
+    /// If this `Body` is for the body of a constant, this will just be
+    /// empty.
+    pub params: Vec<PatId>,
+    /// The `ExprId` of the actual body expression.
+    pub body_expr: ExprId,
+    pub item_scope: ItemScope,
+}
+
+pub type ExprPtr = AstPtr<ast::Expr>;
+pub type ExprSource = InFile<ExprPtr>;
+
+pub type PatPtr = Either<AstPtr<ast::Pat>, AstPtr<ast::SelfParam>>;
+pub type PatSource = InFile<PatPtr>;
+
+/// An item body together with the mapping from syntax nodes to HIR expression
+/// IDs. This is needed to go from e.g. a position in a file to the HIR
+/// expression containing it; but for type inference etc., we want to operate on
+/// a structure that is agnostic to the actual positions of expressions in the
+/// file, so that we don't recompute types whenever some whitespace is typed.
+///
+/// One complication here is that, due to macro expansion, a single `Body` might
+/// be spread across several files. So, for each ExprId and PatId, we record
+/// both the HirFileId and the position inside the file. However, we only store
+/// AST -> ExprId mapping for non-macro files, as it is not clear how to handle
+/// this properly for macros.
+#[derive(Default, Debug, Eq, PartialEq)]
+pub struct BodySourceMap {
+    expr_map: FxHashMap<ExprSource, ExprId>,
+    expr_map_back: ArenaMap<ExprId, Result<ExprSource, SyntheticSyntax>>,
+    pat_map: FxHashMap<PatSource, PatId>,
+    pat_map_back: ArenaMap<PatId, Result<PatSource, SyntheticSyntax>>,
+    field_map: FxHashMap<(ExprId, usize), InFile<AstPtr<ast::RecordExprField>>>,
+    expansions: FxHashMap<InFile<AstPtr<ast::MacroCall>>, HirFileId>,
+}
+
+#[derive(Default, Debug, Eq, PartialEq, Clone, Copy)]
+pub struct SyntheticSyntax;
+
+impl Body {
+    pub(crate) fn body_with_source_map_query(
+        db: &dyn DefDatabase,
+        def: DefWithBodyId,
+    ) -> (Arc<Body>, Arc<BodySourceMap>) {
+        let _p = profile::span("body_with_source_map_query");
+        let mut params = None;
+
+        let (file_id, module, body) = match def {
+            DefWithBodyId::FunctionId(f) => {
+                let f = f.lookup(db);
+                let src = f.source(db);
+                params = src.value.param_list();
+                (src.file_id, f.module(db), src.value.body().map(ast::Expr::from))
+            }
+            DefWithBodyId::ConstId(c) => {
+                let c = c.lookup(db);
+                let src = c.source(db);
+                (src.file_id, c.module(db), src.value.body())
+            }
+            DefWithBodyId::StaticId(s) => {
+                let s = s.lookup(db);
+                let src = s.source(db);
+                (src.file_id, s.module(db), src.value.body())
+            }
+        };
+        let expander = Expander::new(db, file_id, module);
+        let (body, source_map) = Body::new(db, def, expander, params, body);
+        (Arc::new(body), Arc::new(source_map))
+    }
+
+    pub(crate) fn body_query(db: &dyn DefDatabase, def: DefWithBodyId) -> Arc<Body> {
+        db.body_with_source_map(def).0
+    }
+
+    fn new(
+        db: &dyn DefDatabase,
+        def: DefWithBodyId,
+        expander: Expander,
+        params: Option<ast::ParamList>,
+        body: Option<ast::Expr>,
+    ) -> (Body, BodySourceMap) {
+        lower::lower(db, def, expander, params, body)
+    }
+}
+
+impl Index<ExprId> for Body {
+    type Output = Expr;
+
+    fn index(&self, expr: ExprId) -> &Expr {
+        &self.exprs[expr]
+    }
+}
+
+impl Index<PatId> for Body {
+    type Output = Pat;
+
+    fn index(&self, pat: PatId) -> &Pat {
+        &self.pats[pat]
+    }
+}
+
+impl BodySourceMap {
+    pub fn expr_syntax(&self, expr: ExprId) -> Result<ExprSource, SyntheticSyntax> {
+        self.expr_map_back[expr].clone()
+    }
+
+    pub fn node_expr(&self, node: InFile<&ast::Expr>) -> Option<ExprId> {
+        let src = node.map(|it| AstPtr::new(it));
+        self.expr_map.get(&src).cloned()
+    }
+
+    pub fn node_macro_file(&self, node: InFile<&ast::MacroCall>) -> Option<HirFileId> {
+        let src = node.map(|it| AstPtr::new(it));
+        self.expansions.get(&src).cloned()
+    }
+
+    pub fn pat_syntax(&self, pat: PatId) -> Result<PatSource, SyntheticSyntax> {
+        self.pat_map_back[pat].clone()
+    }
+
+    pub fn node_pat(&self, node: InFile<&ast::Pat>) -> Option<PatId> {
+        let src = node.map(|it| Either::Left(AstPtr::new(it)));
+        self.pat_map.get(&src).cloned()
+    }
+
+    pub fn node_self_param(&self, node: InFile<&ast::SelfParam>) -> Option<PatId> {
+        let src = node.map(|it| Either::Right(AstPtr::new(it)));
+        self.pat_map.get(&src).cloned()
+    }
+
+    pub fn field_syntax(&self, expr: ExprId, field: usize) -> InFile<AstPtr<ast::RecordExprField>> {
+        self.field_map[&(expr, field)].clone()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use base_db::{fixture::WithFixture, SourceDatabase};
+    use test_utils::mark;
+
+    use crate::ModuleDefId;
+
+    use super::*;
+
+    fn lower(ra_fixture: &str) -> Arc<Body> {
+        let (db, file_id) = crate::test_db::TestDB::with_single_file(ra_fixture);
+
+        let krate = db.crate_graph().iter().next().unwrap();
+        let def_map = db.crate_def_map(krate);
+        let module = def_map.modules_for_file(file_id).next().unwrap();
+        let module = &def_map[module];
+        let fn_def = match module.scope.declarations().next().unwrap() {
+            ModuleDefId::FunctionId(it) => it,
+            _ => panic!(),
+        };
+
+        db.body(fn_def.into())
+    }
+
+    #[test]
+    fn your_stack_belongs_to_me() {
+        mark::check!(your_stack_belongs_to_me);
+        lower(
+            "
+macro_rules! n_nuple {
+    ($e:tt) => ();
+    ($($rest:tt)*) => {{
+        (n_nuple!($($rest)*)None,)
+    }};
+}
+fn main() { n_nuple!(1,2,3); }
+",
+        );
+    }
+}