instance: always polymorphize substs

By always polymorphizing substitutions, functions which take closures as
arguments (e.g. `impl Fn()`) can have fewer mono items when some of the
argument closures can be polymorphized.

Signed-off-by: David Wood <david@davidtw.co>

1 files changed, 37 insertions, 0 deletions

diff --git a/src/test/codegen-units/polymorphization/pr-75255.rs b/src/test/codegen-units/polymorphization/pr-75255.rs
new file mode 100644
index 00000000000..ea9a6e8b181
--- /dev/null
+++ b/src/test/codegen-units/polymorphization/pr-75255.rs
@@ -0,0 +1,37 @@
+// compile-flags:-Zpolymorphize=on -Zprint-mono-items=lazy -Copt-level=1
+// ignore-tidy-linelength
+
+#![crate_type = "rlib"]
+
+// Test that only one copy of `Iter::map` is generated.
+
+fn foo<T>() {
+    let x = [1, 2, 3, std::mem::size_of::<T>()];
+    x.iter().map(|_| ());
+}
+
+pub fn dispatch() {
+    foo::<String>();
+    foo::<Vec<String>>();
+}
+
+//~ MONO_ITEM fn core::iter[0]::adapters[0]::{{impl}}[29]::new[0]<core::slice[0]::Iter[0]<usize>, pr_75255::foo[0]::{{closure}}[0]<T>> @@ pr_75255-cgu.0[External]
+//~ MONO_ITEM fn core::iter[0]::traits[0]::iterator[0]::Iterator[0]::map[0]<core::slice[0]::Iter[0]<usize>, (), pr_75255::foo[0]::{{closure}}[0]<T>> @@ pr_75255-cgu.1[Internal]
+
+// These are all the items that aren't relevant to the test.
+//~ MONO_ITEM fn core::mem[0]::size_of[0]<alloc::string[0]::String[0]> @@ pr_75255-cgu.1[Internal]
+//~ MONO_ITEM fn core::mem[0]::size_of[0]<alloc::vec[0]::Vec[0]<alloc::string[0]::String[0]>> @@ pr_75255-cgu.1[Internal]
+//~ MONO_ITEM fn core::mem[0]::size_of[0]<usize> @@ pr_75255-cgu.1[Internal]
+//~ MONO_ITEM fn core::ptr[0]::const_ptr[0]::{{impl}}[0]::add[0]<usize> @@ pr_75255-cgu.1[Internal]
+//~ MONO_ITEM fn core::ptr[0]::const_ptr[0]::{{impl}}[0]::is_null[0]<usize> @@ pr_75255-cgu.1[Internal]
+//~ MONO_ITEM fn core::ptr[0]::const_ptr[0]::{{impl}}[0]::offset[0]<usize> @@ pr_75255-cgu.1[Internal]
+//~ MONO_ITEM fn core::ptr[0]::const_ptr[0]::{{impl}}[0]::wrapping_add[0]<u8> @@ pr_75255-cgu.1[Internal]
+//~ MONO_ITEM fn core::ptr[0]::const_ptr[0]::{{impl}}[0]::wrapping_offset[0]<u8> @@ pr_75255-cgu.1[Internal]
+//~ MONO_ITEM fn core::ptr[0]::non_null[0]::{{impl}}[3]::new_unchecked[0]<usize> @@ pr_75255-cgu.1[Internal]
+//~ MONO_ITEM fn core::ptr[0]::null[0]<u8> @@ pr_75255-cgu.1[Internal]
+//~ MONO_ITEM fn core::slice[0]::{{impl}}[0]::as_ptr[0]<usize> @@ pr_75255-cgu.1[Internal]
+//~ MONO_ITEM fn core::slice[0]::{{impl}}[0]::iter[0]<usize> @@ pr_75255-cgu.1[Internal]
+//~ MONO_ITEM fn core::slice[0]::{{impl}}[0]::len[0]<usize> @@ pr_75255-cgu.1[Internal]
+//~ MONO_ITEM fn pr_75255::dispatch[0] @@ pr_75255-cgu.1[External]
+//~ MONO_ITEM fn pr_75255::foo[0]<alloc::string[0]::String[0]> @@ pr_75255-cgu.1[Internal]
+//~ MONO_ITEM fn pr_75255::foo[0]<alloc::vec[0]::Vec[0]<alloc::string[0]::String[0]>> @@ pr_75255-cgu.1[Internal]