Rollup merge of #86484 - fee1-dead:builtin-macro-recursion, r=petrochenkov

Do not set depth to 0 in fully_expand_fragment

Fixes #84632.

src/test/ui/macros/issue-84632-eager-expansion-recursion-limit.rs

@@ -0,0 +1,16 @@
+// Regression test for #84632: Recursion limit is ignored
+// for builtin macros that eagerly expands.
+
+#![recursion_limit = "15"]
+macro_rules! a {
+    () => ("");
+    (A) => (concat!("", a!()));
+    (A, $($A:ident),*) => (concat!("", a!($($A),*)))
+    //~^ ERROR recursion limit reached
+    //~| HELP consider adding
+}
+
+fn main() {
+    a!(A, A, A, A, A);
+    a!(A, A, A, A, A, A, A, A, A, A, A);
+}

src/test/ui/macros/issue-84632-eager-expansion-recursion-limit.stderr

@@ -0,0 +1,14 @@
+error: recursion limit reached while expanding `concat!`
+  --> $DIR/issue-84632-eager-expansion-recursion-limit.rs:8:28
+   |
+LL |     (A, $($A:ident),*) => (concat!("", a!($($A),*)))
+   |                            ^^^^^^^^^^^^^^^^^^^^^^^^
+...
+LL |     a!(A, A, A, A, A, A, A, A, A, A, A);
+   |     ------------------------------------ in this macro invocation
+   |
+   = help: consider adding a `#![recursion_limit="30"]` attribute to your crate (`issue_84632_eager_expansion_recursion_limit`)
+   = note: this error originates in the macro `a` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to previous error
+