From eafa3a888f1aac52a7499fb464414519c434a7ce Mon Sep 17 00:00:00 2001
From: varkor <github@varkor.com>
Date: Thu, 30 May 2019 00:20:52 +0100
Subject: [PATCH 1/2] Sort in-band generic parameter definitions from APIT

---
 src/librustc/hir/lowering.rs | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/src/librustc/hir/lowering.rs b/src/librustc/hir/lowering.rs
index c5bcddcb26623..08fbd0d20d74d 100644
--- a/src/librustc/hir/lowering.rs
+++ b/src/librustc/hir/lowering.rs
@@ -1083,6 +1083,18 @@ impl<'a> LoweringContext<'a> {
             .chain(in_band_defs)
             .collect();
 
+        // FIXME(const_generics): the compiler doesn't always cope with
+        // unsorted generic parameters at the moment, so we make sure
+        // that they're ordered correctly here for now. (When we chain
+        // the `in_band_defs`, we might make the order unsorted.)
+        lowered_generics.params.sort_by_key(|param| {
+            match param.kind {
+                hir::GenericParamKind::Lifetime { .. } => ParamKindOrd::Lifetime,
+                hir::GenericParamKind::Type { .. } => ParamKindOrd::Type,
+                hir::GenericParamKind::Const { .. } => ParamKindOrd::Const,
+            }
+        });
+
         (lowered_generics, res)
     }
 

From 998ef688a39a1b842b5d0a71ea92a8f825650975 Mon Sep 17 00:00:00 2001
From: varkor <github@varkor.com>
Date: Thu, 30 May 2019 00:21:04 +0100
Subject: [PATCH 2/2] Add a regression test for const parameters with impl
 Trait

---
 src/test/ui/const-generics/apit-with-const-param.rs    | 10 ++++++++++
 .../ui/const-generics/apit-with-const-param.stderr     |  6 ++++++
 2 files changed, 16 insertions(+)
 create mode 100644 src/test/ui/const-generics/apit-with-const-param.rs
 create mode 100644 src/test/ui/const-generics/apit-with-const-param.stderr

diff --git a/src/test/ui/const-generics/apit-with-const-param.rs b/src/test/ui/const-generics/apit-with-const-param.rs
new file mode 100644
index 0000000000000..70e718d889029
--- /dev/null
+++ b/src/test/ui/const-generics/apit-with-const-param.rs
@@ -0,0 +1,10 @@
+// run-pass
+
+#![feature(const_generics)]
+//~^ WARN the feature `const_generics` is incomplete and may cause the compiler to crash
+
+trait Trait {}
+
+fn f<const N: usize>(_: impl Trait) {}
+
+fn main() {}
diff --git a/src/test/ui/const-generics/apit-with-const-param.stderr b/src/test/ui/const-generics/apit-with-const-param.stderr
new file mode 100644
index 0000000000000..b3038ee648851
--- /dev/null
+++ b/src/test/ui/const-generics/apit-with-const-param.stderr
@@ -0,0 +1,6 @@
+warning: the feature `const_generics` is incomplete and may cause the compiler to crash
+  --> $DIR/apit-with-const-param.rs:3:12
+   |
+LL | #![feature(const_generics)]
+   |            ^^^^^^^^^^^^^^
+