Fix examples to work with nightly-2025-02-13

While there were comments indicating which nightly versions the examples
were tested with, those versions did not work for me: neither did the
examples compile, nor did they produce the expected output.

This commit fixes the compilation issues, using nightly-2025-02-13 for
all examples (previously the version differed between the examples) and,
in the case of the `rustc_driver` examples, also fixes the argument
passing: rustc ignores the first argument, so we need to pass the
filename as the second (otherwise we only get the help text printed).

Note that the `rustc-interface-getting-diagnostics.rs` example still
does not produce any output, which I assume is not how it is intended.
However, I don't know enough to fix it.

To avoid inconsistencies between the documented version and the actually
required version I've moved the version comment from the Markdown into
the Rust code where it hopefully won't be forgotten as easily.

Finally I've clarified in the examples' README that you also need to use
the proper nightly version when compiling the examples, not just when
running them.

1 files changed, 13 insertions, 3 deletions

diff --git a/src/doc/rustc-dev-guide/examples/rustc-driver-interacting-with-the-ast.rs b/src/doc/rustc-dev-guide/examples/rustc-driver-interacting-with-the-ast.rs
index 9fcb16b0fca..98c6041d0be 100644
--- a/src/doc/rustc-dev-guide/examples/rustc-driver-interacting-with-the-ast.rs
+++ b/src/doc/rustc-dev-guide/examples/rustc-driver-interacting-with-the-ast.rs
@@ -1,3 +1,5 @@
+// Tested with nightly-2025-02-13
+
 #![feature(rustc_private)]
 
 extern crate rustc_ast;
@@ -74,8 +76,8 @@ impl rustc_driver::Callbacks for MyCallbacks {
         for id in hir_krate.items() {
             let item = hir_krate.item(id);
             // 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::ItemKind::Fn { body, .. } = item.kind {
+                let expr = &tcx.hir().body(body).value;
                 if let rustc_hir::ExprKind::Block(block, _) = expr.kind {
                     if let rustc_hir::StmtKind::Let(let_stmt) = block.stmts[0].kind {
                         if let Some(expr) = let_stmt.init {
@@ -94,5 +96,13 @@ impl rustc_driver::Callbacks for MyCallbacks {
 }
 
 fn main() {
-    run_compiler(&["main.rs".to_string()], &mut MyCallbacks);
+    run_compiler(
+        &[
+            // The first argument, which in practice contains the name of the binary being executed
+            // (i.e. "rustc") is ignored by rustc.
+            "ignored".to_string(),
+            "main.rs".to_string(),
+        ],
+        &mut MyCallbacks,
+    );
 }