From 5703b2863e1b4b815007b5a3380734634acd1f37 Mon Sep 17 00:00:00 2001
From: David Wood <david@davidtw.co>
Date: Sun, 16 Aug 2020 16:35:38 +0100
Subject: polymorphize: ∃ used param ∈ predicate → all used
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This commit modifies polymorphization's handling of predicates so that
if any generic parameter is used in a predicate then all parameters in
that predicate are used.

Signed-off-by: David Wood <david@davidtw.co>
---
 src/test/ui/polymorphization/predicates.rs | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

(limited to 'src/test/ui/polymorphization')

diff --git a/src/test/ui/polymorphization/predicates.rs b/src/test/ui/polymorphization/predicates.rs
index 60555dc12dc..97f1ef2c90a 100644
--- a/src/test/ui/polymorphization/predicates.rs
+++ b/src/test/ui/polymorphization/predicates.rs
@@ -60,6 +60,21 @@ where
     std::mem::size_of::<C>()
 }
 
+// Finally, check that `F` is considered used because `G` is used when neither are in the self-ty
+// of the predicate.
+
+trait Foobar<F, G> {}
+
+impl Foobar<u32, u32> for () {}
+
+#[rustc_polymorphize_error]
+fn foobar<F, G>() -> usize
+where
+    (): Foobar<F, G>,
+{
+    std::mem::size_of::<G>()
+}
+
 fn main() {
     let x = &[2u32];
     foo(x.iter());
@@ -69,4 +84,6 @@ fn main() {
     let _ = a.next();
 
     let _ = quux::<u8, u16, u32>();
+
+    let _ = foobar::<u32, u32>();
 }
-- 
cgit 1.4.1-3-g733a5