Warn about invalid mir-enable-passes pass names

Author: clubby789

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/pass_manager.rs

@@ -1,14 +1,14 @@
 use std::cell::RefCell;
 use std::collections::hash_map::Entry;
 
-use rustc_data_structures::fx::FxHashMap;
+use rustc_data_structures::fx::{FxHashMap, FxIndexSet};
 use rustc_middle::mir::{self, Body, MirPhase, RuntimePhase};
 use rustc_middle::ty::TyCtxt;
 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>> = {
@@ -197,6 +197,12 @@ fn run_passes_inner<'tcx>(
 ) {
     let overridden_passes = &tcx.sess.opts.unstable_opts.mir_enable_passes;
     trace!(?overridden_passes);
+    let named_passes =
+        overridden_passes.iter().map(|(name, _)| name.as_str()).collect::<FxIndexSet<_>>();
+    let known_passes = passes.iter().map(|p| p.name()).collect::<FxIndexSet<_>>();
+    for &name in named_passes.difference(&known_passes) {
+        tcx.dcx().emit_warn(errors::UnknownPassName { name });
+    }
 
     let prof_arg = tcx.sess.prof.enabled().then(|| format!("{:?}", body.source.def_id()));
 

tests/ui/mir/invalid_pass_name.rs

@@ -0,0 +1,7 @@
+//@ check-pass
+//@ compile-flags: -Zmir-enable-passes=+ThisPass,-DoesNotExist
+//! Ensure a warning is emitted if unknown pass names are requested
+
+//@ error-pattern: warning: MIR pass `ThisPass` is unknown and will be ignored
+//@ error-pattern: warning: MIR pass `DoesNotExist` is unknown and will be ignored
+fn main() {}

tests/ui/mir/invalid_pass_name.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
+