Add tests for uninferred consts during codegen

Author: varkor

src/test/ui/const-generics/uninferred-consts-during-codegen-1.rs

@@ -0,0 +1,18 @@
+// run-pass
+
+#![feature(const_generics)]
+//~^ WARN the feature `const_generics` is incomplete and may cause the compiler to crash
+
+use std::fmt;
+
+struct Array<T, const N: usize>([T; N]);
+
+impl<T: fmt::Debug, const N: usize> fmt::Debug for Array<T, {N}> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_list().entries(self.0.iter()).finish()
+    }
+}
+
+fn main() {
+    println!("{:?}", Array([1, 2, 3]));
+}

src/test/ui/const-generics/uninferred-consts-during-codegen-1.stderr

@@ -0,0 +1,6 @@
+warning: the feature `const_generics` is incomplete and may cause the compiler to crash
+  --> $DIR/uninferred-consts-during-codegen-1.rs:3:12
+   |
+LL | #![feature(const_generics)]
+   |            ^^^^^^^^^^^^^^
+

src/test/ui/const-generics/uninferred-consts-during-codegen-2.rs

@@ -0,0 +1,18 @@
+// run-pass
+
+#![feature(const_generics)]
+//~^ WARN the feature `const_generics` is incomplete and may cause the compiler to crash
+
+use std::fmt;
+
+struct Array<T>(T);
+
+impl<T: fmt::Debug, const N: usize> fmt::Debug for Array<[T; N]> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_list().entries((&self.0 as &[T]).iter()).finish()
+    }
+}
+
+fn main() {
+    println!("{:?}", Array([1, 2, 3]));
+}

src/test/ui/const-generics/uninferred-consts-during-codegen-2.stderr

@@ -0,0 +1,6 @@
+warning: the feature `const_generics` is incomplete and may cause the compiler to crash
+  --> $DIR/uninferred-consts-during-codegen-2.rs:3:12
+   |
+LL | #![feature(const_generics)]
+   |            ^^^^^^^^^^^^^^
+