add implementation-internal namespace for globalasm

compiler/rustc_symbol_mangling/src/v0.rs

@@ -882,11 +882,11 @@ impl<'tcx> Printer<'tcx> for V0SymbolMangler<'tcx> {
             DefPathData::OpaqueTy => 'i',
             DefPathData::SyntheticCoroutineBody => 's',
             DefPathData::NestedStatic => 'n',
+            DefPathData::GlobalAsm => 'a',
 
             // These should never show up as `print_path_with_simple` arguments.
             DefPathData::CrateRoot
             | DefPathData::Use
-            | DefPathData::GlobalAsm
             | DefPathData::Impl
             | DefPathData::MacroNs(_)
             | DefPathData::LifetimeNs(_)

tests/ui/symbol-names/const-in-global-asm.rs

@@ -0,0 +1,19 @@
+//@ compile-flags: -Clink-dead-code
+//@ build-pass
+
+#![allow(unused)]
+
+// Test that a symbol in a `global_asm` namespace doesn't cause an ICE during v0 symbol mangling
+// due to a lack of missing namespace character for `global_asm`.
+//
+// FIXME: Can't use `#[rustc_symbol_name]` on the `foo` call to check its symbol, so just checking
+// the test compiles.
+
+fn foo<const N: usize>() {}
+
+core::arch::global_asm!("/* {} */", sym foo::<{
+    || {};
+    0
+}>);
+
+fn main() {}