Merge pull request #263 from dtolnay/missingdisplay

Restore UI test involving missing Display impl

Author: dtolnay

tests/ui/missing-display.rs

@@ -0,0 +1,9 @@
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+pub enum MyError {
+    First,
+    Second,
+}
+
+fn main() {}

tests/ui/missing-display.stderr

@@ -0,0 +1,13 @@
+error[E0277]: `MyError` doesn't implement `std::fmt::Display`
+ --> tests/ui/missing-display.rs:4:10
+  |
+4 | pub enum MyError {
+  |          ^^^^^^^ `MyError` cannot be formatted with the default formatter
+  |
+  = help: the trait `std::fmt::Display` is not implemented for `MyError`
+  = note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead
+note: required by a bound in `std::error::Error`
+ --> $RUST/core/src/error.rs
+  |
+  | pub trait Error: Debug + Display {
+  |                          ^^^^^^^ required by this bound in `Error`