Rollup merge of #69836 - JohnTitor:immediate-outputs, r=nagisa

Check if output is immediate value

Fixes #62046

r? @nagisa

src/test/ui/asm/issue-62046.rs

@@ -0,0 +1,11 @@
+// build-fail
+// ignore-emscripten no asm! support
+
+#![feature(asm)]
+
+fn main() {
+    unsafe {
+        asm!("nop" : "+r"("r15"));
+        //~^ malformed inline assembly
+    }
+}

src/test/ui/asm/issue-62046.stderr

@@ -0,0 +1,11 @@
+error[E0668]: malformed inline assembly
+  --> $DIR/issue-62046.rs:8:9
+   |
+LL |         asm!("nop" : "+r"("r15"));
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0668`.