From 37d0d2705de7f4103527ab769e61934c9c4a8953 Mon Sep 17 00:00:00 2001
From: Deadbeef <ent3rm4n@gmail.com>
Date: Mon, 21 Jun 2021 02:05:37 +0800
Subject: [PATCH] Do not set depth to 0 in fully_expand_fragment

---
 compiler/rustc_expand/src/expand.rs              |  2 +-
 ...ssue-84632-eager-expansion-recursion-limit.rs | 16 ++++++++++++++++
 ...-84632-eager-expansion-recursion-limit.stderr | 14 ++++++++++++++
 3 files changed, 31 insertions(+), 1 deletion(-)
 create mode 100644 src/test/ui/macros/issue-84632-eager-expansion-recursion-limit.rs
 create mode 100644 src/test/ui/macros/issue-84632-eager-expansion-recursion-limit.stderr

diff --git a/compiler/rustc_expand/src/expand.rs b/compiler/rustc_expand/src/expand.rs
index 39c0447bd09..37a4765a4be 100644
--- a/compiler/rustc_expand/src/expand.rs
+++ b/compiler/rustc_expand/src/expand.rs
@@ -427,7 +427,6 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
     pub fn fully_expand_fragment(&mut self, input_fragment: AstFragment) -> AstFragment {
         let orig_expansion_data = self.cx.current_expansion.clone();
         let orig_force_mode = self.cx.force_mode;
-        self.cx.current_expansion.depth = 0;
 
         // Collect all macro invocations and replace them with placeholders.
         let (mut fragment_with_placeholders, mut invocations) =
@@ -488,6 +487,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
             };
 
             let ExpansionData { depth, id: expn_id, .. } = invoc.expansion_data;
+            let depth = depth - orig_expansion_data.depth;
             self.cx.current_expansion = invoc.expansion_data.clone();
             self.cx.force_mode = force;
 
diff --git a/src/test/ui/macros/issue-84632-eager-expansion-recursion-limit.rs b/src/test/ui/macros/issue-84632-eager-expansion-recursion-limit.rs
new file mode 100644
index 00000000000..9139775c805
--- /dev/null
+++ b/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);
+}
diff --git a/src/test/ui/macros/issue-84632-eager-expansion-recursion-limit.stderr b/src/test/ui/macros/issue-84632-eager-expansion-recursion-limit.stderr
new file mode 100644
index 00000000000..e6067e33349
--- /dev/null
+++ b/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
+