1 files changed, 142 insertions, 0 deletions

diff --git a/crates/ra_hir_def/src/body.rs b/crates/ra_hir_def/src/body.rs
index 7447904ea..ac8f8261b 100644
--- a/crates/ra_hir_def/src/body.rs
+++ b/crates/ra_hir_def/src/body.rs
@@ -1,2 +1,144 @@
 //! FIXME: write short doc here
 mod lower;
+
+use std::{ops::Index, sync::Arc};
+
+use hir_expand::{either::Either, HirFileId, MacroDefId, Source};
+use ra_arena::{map::ArenaMap, Arena};
+use ra_syntax::{ast, AstPtr};
+use rustc_hash::FxHashMap;
+
+use crate::{
+    db::DefDatabase2,
+    expr::{Expr, ExprId, Pat, PatId},
+    nameres::CrateDefMap,
+    path::Path,
+    ModuleId,
+};
+
+pub struct MacroResolver {
+    crate_def_map: Arc<CrateDefMap>,
+    module: ModuleId,
+}
+
+impl MacroResolver {
+    pub fn new(db: &impl DefDatabase2, module: ModuleId) -> MacroResolver {
+        MacroResolver { crate_def_map: db.crate_def_map(module.krate), module }
+    }
+
+    pub(crate) fn resolve_path_as_macro(
+        &self,
+        db: &impl DefDatabase2,
+        path: &Path,
+    ) -> Option<MacroDefId> {
+        self.crate_def_map.resolve_path(db, self.module.module_id, path).0.get_macros()
+    }
+}
+
+/// The body of an item (function, const etc.).
+#[derive(Debug, Eq, PartialEq)]
+pub struct Body {
+    exprs: Arena<ExprId, Expr>,
+    pats: Arena<PatId, 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.
+    params: Vec<PatId>,
+    /// The `ExprId` of the actual body expression.
+    body_expr: ExprId,
+}
+
+pub type ExprPtr = Either<AstPtr<ast::Expr>, AstPtr<ast::RecordField>>;
+pub type ExprSource = Source<ExprPtr>;
+
+pub type PatPtr = Either<AstPtr<ast::Pat>, AstPtr<ast::SelfParam>>;
+pub type PatSource = Source<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<ExprPtr, ExprId>,
+    expr_map_back: ArenaMap<ExprId, ExprSource>,
+    pat_map: FxHashMap<PatPtr, PatId>,
+    pat_map_back: ArenaMap<PatId, PatSource>,
+    field_map: FxHashMap<(ExprId, usize), AstPtr<ast::RecordField>>,
+}
+
+impl Body {
+    pub fn new(
+        db: &impl DefDatabase2,
+        resolver: MacroResolver,
+        file_id: HirFileId,
+        params: Option<ast::ParamList>,
+        body: Option<ast::Expr>,
+    ) -> (Body, BodySourceMap) {
+        lower::lower(db, resolver, file_id, params, body)
+    }
+
+    pub fn params(&self) -> &[PatId] {
+        &self.params
+    }
+
+    pub fn body_expr(&self) -> ExprId {
+        self.body_expr
+    }
+
+    pub fn exprs(&self) -> impl Iterator<Item = (ExprId, &Expr)> {
+        self.exprs.iter()
+    }
+
+    pub fn pats(&self) -> impl Iterator<Item = (PatId, &Pat)> {
+        self.pats.iter()
+    }
+}
+
+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) -> Option<ExprSource> {
+        self.expr_map_back.get(expr).copied()
+    }
+
+    pub fn node_expr(&self, node: &ast::Expr) -> Option<ExprId> {
+        self.expr_map.get(&Either::A(AstPtr::new(node))).cloned()
+    }
+
+    pub fn pat_syntax(&self, pat: PatId) -> Option<PatSource> {
+        self.pat_map_back.get(pat).copied()
+    }
+
+    pub fn node_pat(&self, node: &ast::Pat) -> Option<PatId> {
+        self.pat_map.get(&Either::A(AstPtr::new(node))).cloned()
+    }
+
+    pub fn field_syntax(&self, expr: ExprId, field: usize) -> AstPtr<ast::RecordField> {
+        self.field_map[&(expr, field)]
+    }
+}