Ensure const impl cannot coexist with non-const impl

Author: ecstatic-morse

src/test/ui/rfc-2632-const-trait-impl/const-and-non-const-impl.rs

@@ -0,0 +1,33 @@
+#![allow(incomplete_features)]
+#![feature(const_trait_impl)]
+
+pub struct Int(i32);
+
+impl const std::ops::Add for i32 {
+    //~^ ERROR conflicting implementations of trait
+    //~| ERROR only traits defined in the current crate can be implemented for arbitrary types
+    type Output = Self;
+
+    fn add(self, rhs: Self) -> Self {
+        self + rhs
+    }
+}
+
+impl std::ops::Add for Int {
+    type Output = Self;
+
+    fn add(self, rhs: Self) -> Self {
+        Int(self.0 + rhs.0)
+    }
+}
+
+impl const std::ops::Add for Int {
+    //~^ ERROR conflicting implementations of trait
+    type Output = Self;
+
+    fn add(self, rhs: Self) -> Self {
+        Int(self.0 + rhs.0)
+    }
+}
+
+fn main() {}

src/test/ui/rfc-2632-const-trait-impl/const-and-non-const-impl.stderr

@@ -0,0 +1,34 @@
+error[E0119]: conflicting implementations of trait `std::ops::Add` for type `i32`:
+  --> $DIR/const-and-non-const-impl.rs:6:1
+   |
+LL | impl const std::ops::Add for i32 {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: conflicting implementation in crate `core`:
+           - impl std::ops::Add for i32;
+
+error[E0119]: conflicting implementations of trait `std::ops::Add` for type `Int`:
+  --> $DIR/const-and-non-const-impl.rs:24:1
+   |
+LL | impl std::ops::Add for Int {
+   | -------------------------- first implementation here
+...
+LL | impl const std::ops::Add for Int {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `Int`
+
+error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
+  --> $DIR/const-and-non-const-impl.rs:6:1
+   |
+LL | impl const std::ops::Add for i32 {
+   | ^^^^^^^^^^^-------------^^^^^---
+   | |          |                 |
+   | |          |                 `i32` is not defined in the current crate
+   | |          `i32` is not defined in the current crate
+   | impl doesn't use only types from inside the current crate
+   |
+   = note: define and implement a trait or new type instead
+
+error: aborting due to 3 previous errors
+
+Some errors have detailed explanations: E0117, E0119.
+For more information about an error, try `rustc --explain E0117`.