## Getting the type of an expression
-To get the type of an expression, use the `global_ctxt` to get a `TyCtxt`:
+To get the type of an expression, use the `global_ctxt` to get a `TyCtxt`.
+The following should be compiled with <!-- date: 2021-03 --> `nightly-2021-03-28`
+(see [here][example] for the complete example):
+
+[example]: https://github.com/rust-lang/rustc-dev-guide/blob/master/examples/rustc-driver-interacting-with-the-ast.rs
```rust
-// See https://github.com/rust-lang/rustc-dev-guide/blob/master/examples/rustc-driver-interacting-with-the-ast.rs for complete program.
let config = rustc_interface::Config {
input: config::Input::Str {
name: source_map::FileName::Custom("main.rs".to_string()),
// Analyze the crate and inspect the types under the cursor.
queries.global_ctxt().unwrap().take().enter(|tcx| {
// Every compilation contains a single crate.
- let krate = tcx.hir().krate();
+ let hir_krate = tcx.hir().krate();
// Iterate over the top-level items in the crate, looking for the main function.
- for (_, item) in &krate.items {
+ for (_, item) in &hir_krate.items {
// Use pattern-matching to find a specific node inside the main function.
if let rustc_hir::ItemKind::Fn(_, _, body_id) = item.kind {
let expr = &tcx.hir().body(body_id).value;
if let rustc_hir::StmtKind::Local(local) = block.stmts[0].kind {
if let Some(expr) = local.init {
let hir_id = expr.hir_id; // hir_id identifies the string "Hello, world!"
- let def_id = tcx.hir().local_def_id(item.hir_id); // def_id identifies the main function
+ let def_id = tcx.hir().local_def_id(item.hir_id()); // def_id identifies the main function
let ty = tcx.typeck(def_id).node_type(hir_id);
println!("{:?}: {:?}", expr, ty); // prints expr(HirId { owner: DefIndex(3), local_id: 4 }: "Hello, world!"): &'static str
}