Add #[default_method_body_is_const]

src/test/ui/rfc-2632-const-trait-impl/impl-with-default-fn.rs

@@ -8,13 +8,31 @@ trait Tr {
         println!("lul");
         self.req();
     }
+
+    #[default_method_body_is_const]
+    fn default() {}
 }
 
 struct S;
 
 impl const Tr for S {
     fn req(&self) {}
+} //~^^ ERROR const trait implementations may not use non-const default functions
+
+impl const Tr for u8 {
+    fn req(&self) {}
+    fn prov(&self) {}
 }
-//~^^^ ERROR const trait implementations may not use default functions
+
+impl const Tr for u16 {
+    fn prov(&self) {}
+    fn default() {}
+} //~^^^ ERROR not all trait items implemented
+
+
+impl const Tr for u32 {
+    fn req(&self) {}
+    fn default() {}
+} //~^^^ ERROR const trait implementations may not use non-const default functions
 
 fn main() {}

src/test/ui/rfc-2632-const-trait-impl/impl-with-default-fn.stderr

@@ -1,10 +1,33 @@
-error: const trait implementations may not use default functions
-  --> $DIR/impl-with-default-fn.rs:15:1
+error: const trait implementations may not use non-const default functions
+  --> $DIR/impl-with-default-fn.rs:18:1
    |
 LL | / impl const Tr for S {
 LL | |     fn req(&self) {}
 LL | | }
    | |_^
+   |
+   = note: `prov` not implemented
 
-error: aborting due to previous error
+error: const trait implementations may not use non-const default functions
+  --> $DIR/impl-with-default-fn.rs:33:1
+   |
+LL | / impl const Tr for u32 {
+LL | |     fn req(&self) {}
+LL | |     fn default() {}
+LL | | }
+   | |_^
+   |
+   = note: `prov` not implemented
 
+error[E0046]: not all trait items implemented, missing: `req`
+  --> $DIR/impl-with-default-fn.rs:27:1
+   |
+LL |     fn req(&self);
+   |     -------------- `req` from trait
+...
+LL | impl const Tr for u16 {
+   | ^^^^^^^^^^^^^^^^^^^^^ missing `req` in implementation
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0046`.