uncopypaste def sources

crates/ra_hir/src/code_model_impl.rs

@@ -1,3 +1,18 @@
 mod krate; // `crate` is invalid ident :(
 mod module;
 pub(crate) mod function;
+
+use ra_syntax::{AstNode, TreeArc};
+
+use crate::{HirDatabase, DefId, HirFileId};
+
+pub(crate) fn def_id_to_ast<N: AstNode>(
+    db: &impl HirDatabase,
+    def_id: DefId,
+) -> (HirFileId, TreeArc<N>) {
+    let (file_id, syntax) = def_id.source(db);
+    let ast = N::cast(&syntax)
+        .unwrap_or_else(|| panic!("def points to wrong source {:?} {:?}", def_id, syntax))
+        .to_owned();
+    (file_id, ast)
+}