Validate and test -Zmir-enable-passes

compiler/rustc_mir_transform/messages.ftl

@@ -34,3 +34,5 @@ mir_transform_undefined_transmute = pointers cannot be transmuted to integers du
     .note = at compile-time, pointers do not have an integer value
     .note2 = avoiding this restriction via `union` or raw pointers leads to compile-time undefined behavior
     .help = for more information, see https://doc.rust-lang.org/std/mem/fn.transmute.html
+
+mir_transform_unknown_pass_name = MIR pass `{$name}` is unknown and will be ignored

compiler/rustc_mir_transform/src/errors.rs

@@ -38,6 +38,12 @@ pub(crate) struct UnalignedPackedRef {
     pub span: Span,
 }
 
+#[derive(Diagnostic)]
+#[diag(mir_transform_unknown_pass_name)]
+pub(crate) struct UnknownPassName<'a> {
+    pub(crate) name: &'a str,
+}
+
 pub(crate) struct AssertLint<P> {
     pub span: Span,
     pub assert_kind: AssertKind<P>,

compiler/rustc_mir_transform/src/lib.rs

@@ -90,7 +90,6 @@ macro_rules! declare_passes {
             )+
         )*
 
-        #[cfg(debug_assertions)]
         static PASS_NAMES: LazyLock<Vec<String>> = LazyLock::new(|| vec![
             // Fake marker pass
             "PreCodegen".to_string(),

compiler/rustc_mir_transform/src/pass_manager.rs

@@ -8,7 +8,7 @@ use rustc_session::Session;
 use tracing::trace;
 
 use crate::lint::lint_body;
-use crate::validate;
+use crate::{errors, validate};
 
 thread_local! {
     static PASS_NAMES: RefCell<FxHashMap<&'static str, &'static str>> = {
@@ -198,13 +198,29 @@ fn run_passes_inner<'tcx>(
     let overridden_passes = &tcx.sess.opts.unstable_opts.mir_enable_passes;
     trace!(?overridden_passes);
 
-    #[cfg(debug_assertions)]
-    {
-        let used_passes: FxIndexSet<_> = passes.iter().map(|p| p.name()).collect();
+    let named_passes: FxIndexSet<_> =
+        overridden_passes.iter().map(|(name, _)| name.as_str()).collect();
     let known_passes: FxIndexSet<_> = crate::PASS_NAMES.iter().map(|p| p.as_str()).collect();
 
-        for &name in used_passes.difference(&known_passes) {
-            tcx.dcx().bug(format!("pass `{name}` is not declared in `PASS_NAMES`"));
+    for &name in named_passes.difference(&known_passes) {
+        tcx.dcx().emit_warn(errors::UnknownPassName { name });
+    }
+
+    // Verify that no passes are missing from the `declare_passes` invocation
+    #[cfg(debug_assertions)]
+    #[allow(rustc::diagnostic_outside_of_impl)]
+    #[allow(rustc::untranslatable_diagnostic)]
+    {
+        let used_passes: FxIndexSet<_> = passes.iter().map(|p| p.name()).collect();
+
+        let undeclared = used_passes.difference(&known_passes).collect::<Vec<_>>();
+        if let Some((name, rest)) = undeclared.split_first() {
+            let mut err =
+                tcx.dcx().struct_bug(format!("pass `{name}` is not declared in `PASS_NAMES`"));
+            for name in rest {
+                err.note(format!("pass `{name}` is also not declared in `PASS_NAMES`"));
+            }
+            err.emit();
         }
     }
 

tests/ui/mir/enable_passes_validation.all_unknown.stderr

@@ -0,0 +1,14 @@
+warning: MIR pass `ThisPass` is unknown and will be ignored
+
+warning: MIR pass `DoesNotExist` is unknown and will be ignored
+
+warning: MIR pass `ThisPass` is unknown and will be ignored
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+warning: MIR pass `DoesNotExist` is unknown and will be ignored
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+warning: 4 warnings emitted
+

tests/ui/mir/enable_passes_validation.empty.stderr

@@ -0,0 +1,2 @@
+error: incorrect value `` for unstable option `mir-enable-passes` - a comma-separated list of strings, with elements beginning with + or - was expected
+

tests/ui/mir/enable_passes_validation.mixed.stderr

@@ -0,0 +1,8 @@
+warning: MIR pass `ThisPassDoesNotExist` is unknown and will be ignored
+
+warning: MIR pass `ThisPassDoesNotExist` is unknown and will be ignored
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+warning: 2 warnings emitted
+

tests/ui/mir/enable_passes_validation.rs

@@ -0,0 +1,21 @@
+//@ revisions: empty unprefixed all_unknown all_known mixed
+
+//@[empty] compile-flags: -Zmir-enable-passes=
+//@[empty] error-pattern error: incorrect value `` for unstable option `mir-enable-passes` - a comma-separated list of strings, with elements beginning with + or - was expected
+
+//@[unprefixed] compile-flags: -Zmir-enable-passes=CheckAlignment
+//@[unprefixed] error-pattern error: incorrect value `CheckAlignment` for unstable option `mir-enable-passes` - a comma-separated list of strings, with elements beginning with + or - was expected
+
+//@[all_unknown] check-pass
+//@[all_unknown] compile-flags: -Zmir-enable-passes=+ThisPass,-DoesNotExist
+//@[all_unknown] error-pattern: warning: MIR pass `ThisPass` is unknown and will be ignored
+//@[all_unknown] error-pattern: warning: MIR pass `DoesNotExist` is unknown and will be ignored
+
+//@[all_known] check-pass
+//@[all_known] compile-flags: -Zmir-enable-passes=+CheckAlignment,+LowerIntrinsics
+
+//@[mixed] check-pass
+//@[mixed] compile-flags: -Zmir-enable-passes=+ThisPassDoesNotExist,+CheckAlignment
+//@[mixed] error-pattern: warning: MIR pass `ThisPassDoesNotExist` is unknown and will be ignored
+
+fn main() {}

tests/ui/mir/enable_passes_validation.unprefixed.stderr

@@ -0,0 +1,2 @@
+error: incorrect value `CheckAlignment` for unstable option `mir-enable-passes` - a comma-separated list of strings, with elements beginning with + or - was expected
+