Demonstrate excessive stack usage

Use this to run the test:

  cargo test --package ra_hir_ty --lib --release -- \
      tests::regression::your_stack_belongs_to_me --exact --nocapture

You can uncomment more branches to see the effect on stack usage.

It seems that we use Sum(branches) in debug, and Max(branches) in
release (as measured by the final depth before SO).

Author: matklad

crates/ra_hir_def/src/body.rs

@@ -1,9 +1,26 @@
 //! Defines `Body`: a lowered representation of bodies of functions, statics and
 //! consts.
+
+pub(crate) static STACK: AtomicUsize = AtomicUsize::new(0);
+
+macro_rules! stack {
+    ($name:literal) => {
+        let anchor = 92;
+        let addr = &anchor as *const _ as usize;
+        let prev = crate::body::STACK.swap(addr, std::sync::atomic::Ordering::Relaxed);
+        let diff = prev.saturating_sub(addr);
+        eprintln!("{:10} {}", $name, diff / std::mem::size_of::<usize>());
+    };
+}
+
 mod lower;
 pub mod scope;
 
-use std::{mem, ops::Index, sync::Arc};
+use std::{
+    mem,
+    ops::Index,
+    sync::{atomic::AtomicUsize, Arc},
+};
 
 use drop_bomb::DropBomb;
 use either::Either;
@@ -91,6 +108,7 @@ impl Expander {
         local_scope: Option<&ItemScope>,
         macro_call: ast::MacroCall,
     ) -> Option<(Mark, T)> {
+        eprintln!("{:?}", self.recursive_limit);
         if self.recursive_limit > 1024 {
             return None;
         }