Check for llvm_asm in a const context

src/librustc_mir/transform/check_consts/ops.rs

@@ -147,6 +147,10 @@ impl NonConstOp for IfOrMatch {
     }
 }
 
+#[derive(Debug)]
+pub struct InlineAsm;
+impl NonConstOp for InlineAsm {}
+
 #[derive(Debug)]
 pub struct LiveDrop;
 impl NonConstOp for LiveDrop {

src/librustc_mir/transform/check_consts/validation.rs

@@ -481,11 +481,14 @@ impl Visitor<'tcx> for Validator<'_, 'mir, 'tcx> {
             StatementKind::FakeRead(FakeReadCause::ForMatchedPlace, _) => {
                 self.check_op(ops::IfOrMatch);
             }
+            StatementKind::LlvmInlineAsm { .. } => {
+                self.check_op(ops::InlineAsm);
+            }
+
             // FIXME(eddyb) should these really do nothing?
             StatementKind::FakeRead(..)
             | StatementKind::StorageLive(_)
             | StatementKind::StorageDead(_)
-            | StatementKind::LlvmInlineAsm { .. }
             | StatementKind::Retag { .. }
             | StatementKind::AscribeUserType(..)
             | StatementKind::Nop => {}

src/test/ui/consts/inline_asm.rs

@@ -0,0 +1,6 @@
+#![feature(llvm_asm)]
+
+const _: () = unsafe { llvm_asm!("nop") };
+//~^ ERROR contains unimplemented expression type
+
+fn main() {}

src/test/ui/consts/inline_asm.stderr

@@ -0,0 +1,9 @@
+error[E0019]: constant contains unimplemented expression type
+  --> $DIR/inline_asm.rs:3:1
+   |
+LL | const _: () = unsafe { llvm_asm!("nop") };
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0019`.