Tweak the lint and add a Miri test

Author: saethlin

compiler/rustc_lint/src/lints.rs

@@ -3974,6 +3974,6 @@ pub(crate) struct MalformedOnConstAttrLint {
 #[note("this method was used to add checks to the `Eq` derive macro")]
 pub(crate) struct EqInternalMethodImplemented;
 
-#[derive(LintDiagnostic)]
+#[derive(Diagnostic)]
 #[diag("this function could have the attribute #[rustc_panic_entrypoint]")]
 pub(crate) struct MissingPanicEntrypoint;

src/tools/miri/src/eval.rs

@@ -288,14 +288,16 @@ pub fn create_ecx<'tcx>(
         MiriMachine::new(config, layout_cx, genmc_ctx),
     );
 
-    // Make sure we have MIR. We check MIR for some stable monomorphic function in libcore.
-    let sentinel =
-        helpers::try_resolve_path(tcx, &["core", "ascii", "escape_default"], Namespace::ValueNS);
-    if !matches!(sentinel, Some(s) if tcx.is_mir_available(s.def.def_id())) {
-        tcx.dcx().fatal(
-            "the current sysroot was built without `-Zalways-encode-mir`, or libcore seems missing.\n\
-            Note that directly invoking the `miri` binary is not supported; please use `cargo miri` instead."
-        );
+    if !rustc_hir::find_attr!(tcx, crate, NoCore(..)) {
+        // Make sure we have MIR. We check MIR for some stable monomorphic function in libcore.
+        let sentinel =
+            helpers::try_resolve_path(tcx, &["core", "ascii", "escape_default"], Namespace::ValueNS);
+        if !matches!(sentinel, Some(s) if tcx.is_mir_available(s.def.def_id())) {
+            tcx.dcx().fatal(
+                "the current sysroot was built without `-Zalways-encode-mir`, or libcore seems missing.\n\
+                Note that directly invoking the `miri` binary is not supported; please use `cargo miri` instead."
+            );
+        }
     }
 
     // Compute argc and argv from `config.args`.

src/tools/miri/tests/fail/immediate-abort.rs

@@ -0,0 +1,46 @@
+// Test that when we call a function with #[rustc_panic_entrypoint], we encounter an abort and do
+// not actually execute the function. Immediate-aborting panics are implemented by a rewrite of such
+// functions, so this tests that the rewrite works with Miri.
+
+//@compile-flags: -Cpanic=immediate-abort -Zunstable-options --target=x86_64-unknown-none
+
+#![no_std]
+#![no_core]
+#![no_main]
+#![feature(rustc_attrs, no_core, lang_items, intrinsics)]
+#![allow(internal_features)]
+
+#[lang = "pointee_sized"]
+#[diagnostic::on_unimplemented(
+    message = "values of type `{Self}` may or may not have a size",
+    label = "may or may not have a known size"
+)]
+pub trait PointeeSized {}
+
+#[lang = "meta_sized"]
+#[diagnostic::on_unimplemented(
+    message = "the size for values of type `{Self}` cannot be known",
+    label = "doesn't have a known size"
+)]
+pub trait MetaSized: PointeeSized {}
+
+#[lang = "sized"]
+#[diagnostic::on_unimplemented(
+    message = "the size for values of type `{Self}` cannot be known at compilation time",
+    label = "doesn't have a size known at compile-time"
+)]
+pub trait Sized: MetaSized {}
+
+#[rustc_nounwind]
+#[rustc_intrinsic]
+#[lang = "abort_intrinsic"]
+fn abort() -> !;
+
+#[no_mangle]
+fn miri_start(_argc: isize, _argv: *const *const u8) -> isize {
+    panic_entrypoint(); //~ ERROR: abnormal termination: the program aborted execution
+    0
+}
+
+#[rustc_panic_entrypoint]
+fn panic_entrypoint() {}

src/tools/miri/tests/fail/immediate-abort.stderr

@@ -0,0 +1,8 @@
+error: abnormal termination: the program aborted execution
+  --> tests/fail/immediate-abort.rs:LL:CC
+   |
+LL |     panic_entrypoint();
+   |     ^^^^^^^^^^^^^^^^^^ abnormal termination occurred here
+
+error: aborting due to 1 previous error
+