Rollup merge of #109109 - compiler-errors:polymorphize-foreign, r=Nilstrieb

Use `unused_generic_params` from crate metadata

Due to the way that `separate_provide_extern` interacted with the implementation of `<ty::InstanceDef<'tcx> as Key>::query_crate_is_local`, we actually never hit the foreign provider for `unused_generic_params`.

Additionally, since the *local* provider of `unused_generic_params` calls `should_polymorphize`, which always returns false if the def-id is foreign, this means that we never actually polymorphize monomorphic instances originating from foreign crates.

We don't actually encode `unused_generic_params` for items where all generics are used, so I had to tweak the foreign provider to fall back to `ty::UnusedGenericParams::new_all_used()` to avoid more ICEs when the above bugs were fixed.

2 files changed, 15 insertions, 0 deletions

diff --git a/tests/codegen-units/polymorphization/auxiliary/poly-dep.rs b/tests/codegen-units/polymorphization/auxiliary/poly-dep.rs
new file mode 100644
index 00000000000..fdbfa1b096d
--- /dev/null
+++ b/tests/codegen-units/polymorphization/auxiliary/poly-dep.rs
@@ -0,0 +1,4 @@
+// compile-flags: -Zpolymorphize=on
+
+#[inline(never)]
+pub fn foo<T>() {}
diff --git a/tests/codegen-units/polymorphization/poly-foreign.rs b/tests/codegen-units/polymorphization/poly-foreign.rs
new file mode 100644
index 00000000000..9da082daf11
--- /dev/null
+++ b/tests/codegen-units/polymorphization/poly-foreign.rs
@@ -0,0 +1,11 @@
+// aux-build:poly-dep.rs
+// compile-flags: --crate-type=lib -Zprint-mono-items=eager -Zpolymorphize=on
+
+extern crate poly_dep;
+
+pub static FN1: fn() = poly_dep::foo::<i32>;
+pub static FN2: fn() = poly_dep::foo::<u32>;
+
+//~ MONO_ITEM static FN1
+//~ MONO_ITEM static FN2
+//~ MONO_ITEM fn poly_dep::foo::<T>