Normalize closure instance before eagerly monomorphizing it

Author: compiler-errors

compiler/rustc_monomorphize/src/collector.rs

@@ -1509,6 +1509,13 @@ impl<'v> RootCollector<'_, 'v> {
                         }
                         _ => unreachable!(),
                     };
+                    let Ok(instance) = self.tcx.try_normalize_erasing_regions(
+                        ty::TypingEnv::fully_monomorphized(),
+                        instance,
+                    ) else {
+                        // Don't ICE on an impossible-to-normalize closure.
+                        return;
+                    };
                     let mono_item = create_fn_mono_item(self.tcx, instance, DUMMY_SP);
                     if mono_item.node.is_instantiable(self.tcx) {
                         self.output.push(mono_item);

tests/ui/closures/eager-mono-with-normalizable-upvars.rs

@@ -0,0 +1,19 @@
+//@ compile-flags: -Zprint-mono-items=eager -Csymbol-mangling-version=v0
+//@ build-pass
+
+// Ensure that when eagerly collecting `test::{closure#0}`, we don't try
+// collecting an unnormalized version of the closure (specifically its
+// upvars), since the closure captures the RPIT `opaque::{opaque#0}`.
+
+fn opaque() -> impl Sized {}
+
+fn test() -> impl FnOnce() {
+    let opaque = opaque();
+    move || {
+        let opaque = opaque;
+    }
+}
+
+fn main() {
+    test()();
+}

tests/ui/closures/eager-mono-with-normalizable-upvars.stdout

@@ -0,0 +1,12 @@
+MONO_ITEM fn <() as std::process::Termination>::report @@ eager_mono_with_normalizable_upvars.b15aab124d22de9b-cgu.0[Internal]
+MONO_ITEM fn <fn() as std::ops::FnOnce<()>>::call_once - shim(fn()) @@ eager_mono_with_normalizable_upvars.b15aab124d22de9b-cgu.0[Internal]
+MONO_ITEM fn <{closure@std::rt::lang_start<()>::{closure#0}} as std::ops::FnOnce<()>>::call_once - shim @@ eager_mono_with_normalizable_upvars.b15aab124d22de9b-cgu.0[Internal]
+MONO_ITEM fn <{closure@std::rt::lang_start<()>::{closure#0}} as std::ops::FnOnce<()>>::call_once - shim(vtable) @@ eager_mono_with_normalizable_upvars.b15aab124d22de9b-cgu.0[Internal]
+MONO_ITEM fn main @@ eager_mono_with_normalizable_upvars.b15aab124d22de9b-cgu.0[Internal]
+MONO_ITEM fn opaque @@ eager_mono_with_normalizable_upvars.b15aab124d22de9b-cgu.0[Internal]
+MONO_ITEM fn std::ptr::drop_in_place::<{closure@std::rt::lang_start<()>::{closure#0}}> - shim(None) @@ eager_mono_with_normalizable_upvars.b15aab124d22de9b-cgu.0[Internal]
+MONO_ITEM fn std::rt::lang_start::<()> @@ eager_mono_with_normalizable_upvars.b15aab124d22de9b-cgu.0[External]
+MONO_ITEM fn std::rt::lang_start::<()>::{closure#0} @@ eager_mono_with_normalizable_upvars.b15aab124d22de9b-cgu.0[Internal]
+MONO_ITEM fn std::sys::backtrace::__rust_begin_short_backtrace::<fn(), ()> @@ eager_mono_with_normalizable_upvars.b15aab124d22de9b-cgu.0[Internal]
+MONO_ITEM fn test @@ eager_mono_with_normalizable_upvars.b15aab124d22de9b-cgu.0[Internal]
+MONO_ITEM fn test::{closure#0} @@ eager_mono_with_normalizable_upvars.b15aab124d22de9b-cgu.0[Internal]