Add regression test for impl associated items sorting

Author: GuillaumeGomez

tests/rustdoc/impl-associated-items-order.rs

@@ -0,0 +1,42 @@
+// This test ensures that impl associated items always follow this order:
+//
+// 1. Types
+// 2. Consts
+// 3. Functions
+
+#![feature(inherent_associated_types)]
+#![allow(incomplete_features)]
+#![crate_name = "foo"]
+
+//@ has 'foo/struct.Bar.html'
+pub struct Bar;
+
+impl Bar {
+    //@ has - '//*[@id="implementations-list"]//*[@class="impl-items"]/section[3]/h4' \
+    // 'pub fn foo()'
+    pub fn foo() {}
+    //@ has - '//*[@id="implementations-list"]//*[@class="impl-items"]/section[2]/h4' \
+    // 'pub const X: u8 = 12u8'
+    pub const X: u8 = 12;
+    //@ has - '//*[@id="implementations-list"]//*[@class="impl-items"]/section[1]/h4' \
+    // 'pub type Y = u8'
+    pub type Y = u8;
+}
+
+pub trait Foo {
+    const W: u32;
+    fn yeay();
+    type Z;
+}
+
+impl Foo for Bar {
+    //@ has - '//*[@id="trait-implementations-list"]//*[@class="impl-items"]/section[2]/h4' \
+    // 'const W: u32 = 12u32'
+    const W: u32 = 12;
+    //@ has - '//*[@id="trait-implementations-list"]//*[@class="impl-items"]/section[1]/h4' \
+    // 'type Z = u8'
+    type Z = u8;
+    //@ has - '//*[@id="trait-implementations-list"]//*[@class="impl-items"]/section[3]/h4' \
+    // 'fn yeay()'
+    fn yeay() {}
+}