src/doc/rustc-dev-guide/examples/rustc-driver-interacting-with-the-ast.rs

   1 #![feature(rustc_private)]
   2
   3 extern crate rustc_ast_pretty;
   4 extern crate rustc_driver;
   5 extern crate rustc_error_codes;
   6 extern crate rustc_errors;
   7 extern crate rustc_hash;
   8 extern crate rustc_hir;
   9 extern crate rustc_interface;
  10 extern crate rustc_session;
  11 extern crate rustc_span;
  12
  13 use std::{path, process, str};
  14
  15 use rustc_ast_pretty::pprust::item_to_string;
  16 use rustc_errors::registry;
  17 use rustc_session::config::{self, CheckCfg};
  18 use rustc_span::source_map;
  19
  20 fn main() {
  21     let out = process::Command::new("rustc")
  22         .arg("--print=sysroot")
  23         .current_dir(".")
  24         .output()
  25         .unwrap();
  26     let sysroot = str::from_utf8(&out.stdout).unwrap().trim();
  27     let config = rustc_interface::Config {
  28         opts: config::Options {
  29             maybe_sysroot: Some(path::PathBuf::from(sysroot)),
  30             ..config::Options::default()
  31         },
  32         input: config::Input::Str {
  33             name: source_map::FileName::Custom("main.rs".to_string()),
  34             input: r#"
  35 fn main() {
  36     let message = "Hello, World!";
  37     println!("{message}");
  38 }
  39 "#
  40             .to_string(),
  41         },
  42         crate_cfg: rustc_hash::FxHashSet::default(),
  43         crate_check_cfg: CheckCfg::default(),
  44         output_dir: None,
  45         output_file: None,
  46         file_loader: None,
  47         locale_resources: rustc_driver::DEFAULT_LOCALE_RESOURCES,
  48         lint_caps: rustc_hash::FxHashMap::default(),
  49         parse_sess_created: None,
  50         register_lints: None,
  51         override_queries: None,
  52         make_codegen_backend: None,
  53         registry: registry::Registry::new(&rustc_error_codes::DIAGNOSTICS),
  54     };
  55     rustc_interface::run_compiler(config, |compiler| {
  56         compiler.enter(|queries| {
  57             // TODO: add this to -Z unpretty
  58             let ast_krate = queries.parse().unwrap().get_mut().clone();
  59             for item in ast_krate.items {
  60                 println!("{}", item_to_string(&item));
  61             }
  62             // Analyze the crate and inspect the types under the cursor.
  63             queries.global_ctxt().unwrap().enter(|tcx| {
  64                 // Every compilation contains a single crate.
  65                 let hir_krate = tcx.hir();
  66                 // Iterate over the top-level items in the crate, looking for the main function.
  67                 for id in hir_krate.items() {
  68                     let item = hir_krate.item(id);
  69                     // Use pattern-matching to find a specific node inside the main function.
  70                     if let rustc_hir::ItemKind::Fn(_, _, body_id) = item.kind {
  71                         let expr = &tcx.hir().body(body_id).value;
  72                         if let rustc_hir::ExprKind::Block(block, _) = expr.kind {
  73                             if let rustc_hir::StmtKind::Local(local) = block.stmts[0].kind {
  74                                 if let Some(expr) = local.init {
  75                                     let hir_id = expr.hir_id; // hir_id identifies the string "Hello, world!"
  76                                     let def_id = item.hir_id().owner.def_id; // def_id identifies the main function
  77                                     let ty = tcx.typeck(def_id).node_type(hir_id);
  78                                     println!("{expr:#?}: {ty:?}");
  79                                 }
  80                             }
  81                         }
  82                     }
  83                 }
  84             })
  85         });
  86     });
  87 }