Auto merge of #130337 - BoxyUwU:anon_const_macro_call, r=camelid

Fix anon const def-creation when macros are involved take 2

Fixes #130321

There were two cases that #129137 did not handle correctly:

- Given a const argument `Foo<{ bar!() }>` in which `bar!()` expands to `N`, we would visit the anon const and then visit the `{ bar() }` expression instead of visiting the macro call. This meant that we would build a def for the anon const as `{ bar!() }` is not a trivial const argument as `bar!()` is not a path.
- Given a const argument `Foo<{ bar!() }>` is which `bar!()` expands to `{ qux!() }` in which `qux!()` expands to `N`, it should not be considered a trivial const argument as `{{ N }}` has two pairs of braces.  If we only looked at `qux`'s expansion it would *look* like a trivial const argument even though it is not. We have to track whether we have "unwrapped" a brace already when recursing into the expansions of `bar`/`qux`/any macro

r? `@camelid`

1 files changed, 5 insertions, 0 deletions

diff --git a/compiler/rustc_resolve/src/lib.rs b/compiler/rustc_resolve/src/lib.rs
index c05bd9e72ea..3bb1f6b52a7 100644
--- a/compiler/rustc_resolve/src/lib.rs
+++ b/compiler/rustc_resolve/src/lib.rs
@@ -190,6 +190,11 @@ impl InvocationParent {
 
 #[derive(Copy, Debug, Clone)]
 struct PendingAnonConstInfo {
+    // A const arg is only a "trivial" const arg if it has at *most* one set of braces
+    // around the argument. We track whether we have stripped an outter brace so that
+    // if a macro expands to a braced expression *and* the macro was itself inside of
+    // some braces then we can consider it to be a non-trivial const argument.
+    block_was_stripped: bool,
     id: NodeId,
     span: Span,
 }