From 8ecd931a8eb0bb9bde2e7d35e72553b512d01c80 Mon Sep 17 00:00:00 2001
From: Aaron Hill <aa1ronham@gmail.com>
Date: Thu, 25 Mar 2021 15:40:50 -0400
Subject: [PATCH] Don't ICE when using `#[global_alloc]` on a non-item
 statement

Fixes #83469

We need to return an `Annotatable::Stmt` if we were passed an
`Annotatable::Stmt`
---
 .../src/global_allocator.rs                   | 34 +++++++++----------
 .../issue-83469-global-alloc-invalid-stmt.rs  | 10 ++++++
 ...sue-83469-global-alloc-invalid-stmt.stderr |  8 +++++
 3 files changed, 35 insertions(+), 17 deletions(-)
 create mode 100644 src/test/ui/proc-macro/issue-83469-global-alloc-invalid-stmt.rs
 create mode 100644 src/test/ui/proc-macro/issue-83469-global-alloc-invalid-stmt.stderr

diff --git a/compiler/rustc_builtin_macros/src/global_allocator.rs b/compiler/rustc_builtin_macros/src/global_allocator.rs
index 9b43c11f0f3..a97cac7e514 100644
--- a/compiler/rustc_builtin_macros/src/global_allocator.rs
+++ b/compiler/rustc_builtin_macros/src/global_allocator.rs
@@ -14,31 +14,31 @@ pub fn expand(
     ecx: &mut ExtCtxt<'_>,
     _span: Span,
     meta_item: &ast::MetaItem,
-    mut item: Annotatable,
+    item: Annotatable,
 ) -> Vec<Annotatable> {
     check_builtin_macro_attribute(ecx, meta_item, sym::global_allocator);
 
-    let not_static = |item: Annotatable| {
-        ecx.sess.parse_sess.span_diagnostic.span_err(item.span(), "allocators must be statics");
-        vec![item]
-    };
     let orig_item = item.clone();
-    let mut is_stmt = false;
+    let not_static = || {
+        ecx.sess.parse_sess.span_diagnostic.span_err(item.span(), "allocators must be statics");
+        vec![orig_item.clone()]
+    };
 
     // Allow using `#[global_allocator]` on an item statement
-    if let Annotatable::Stmt(stmt) = &item {
-        if let StmtKind::Item(item_) = &stmt.kind {
-            item = Annotatable::Item(item_.clone());
-            is_stmt = true;
-        }
-    }
-
-    let item = match item {
+    // FIXME - if we get deref patterns, use them to reduce duplication here
+    let (item, is_stmt) = match &item {
         Annotatable::Item(item) => match item.kind {
-            ItemKind::Static(..) => item,
-            _ => return not_static(Annotatable::Item(item)),
+            ItemKind::Static(..) => (item, false),
+            _ => return not_static(),
         },
-        _ => return not_static(item),
+        Annotatable::Stmt(stmt) => match &stmt.kind {
+            StmtKind::Item(item_) => match item_.kind {
+                ItemKind::Static(..) => (item_, true),
+                _ => return not_static(),
+            },
+            _ => return not_static(),
+        },
+        _ => return not_static(),
     };
 
     // Generate a bunch of new items using the AllocFnFactory
diff --git a/src/test/ui/proc-macro/issue-83469-global-alloc-invalid-stmt.rs b/src/test/ui/proc-macro/issue-83469-global-alloc-invalid-stmt.rs
new file mode 100644
index 00000000000..25adc5d2578
--- /dev/null
+++ b/src/test/ui/proc-macro/issue-83469-global-alloc-invalid-stmt.rs
@@ -0,0 +1,10 @@
+// Regression test for issue #83469
+// Ensures that we recover from `#[global_alloc]` on an invalid
+// stmt without an ICE
+
+fn outer() {
+    #[global_allocator]
+    fn inner() {} //~ ERROR allocators must be statics
+}
+
+fn main() {}
diff --git a/src/test/ui/proc-macro/issue-83469-global-alloc-invalid-stmt.stderr b/src/test/ui/proc-macro/issue-83469-global-alloc-invalid-stmt.stderr
new file mode 100644
index 00000000000..ec0e3c4c754
--- /dev/null
+++ b/src/test/ui/proc-macro/issue-83469-global-alloc-invalid-stmt.stderr
@@ -0,0 +1,8 @@
+error: allocators must be statics
+  --> $DIR/issue-83469-global-alloc-invalid-stmt.rs:7:5
+   |
+LL |     fn inner() {}
+   |     ^^^^^^^^^^^^^
+
+error: aborting due to previous error
+