Add test of consteval error with notes

Author: dtolnay

src/tests/consteval.rs

@@ -0,0 +1,55 @@
+test_normalize! {
+    WORKSPACE="/git/monostate"
+"
+error[E0080]: evaluation panicked: assertion failed: N == mem::size_of::<T::Type>()
+  --> /git/monostate/src/string.rs:46:13
+   |
+46 |             assert!(N == mem::size_of::<T::Type>());
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ evaluation of `<(monostate::alphabet::len<8>, (monostate::alphabet::char<'a'>, monostate::alphabet::char<'s'>, monostate::alphabet::char<'d'>, monostate::alphabet::char<'f'>)) as monostate::string::Sealed>::__private::{constant#0}` failed here
+
+note: erroneous constant encountered
+  --> /git/monostate/src/string.rs:45:9
+   |
+45 | /         const {
+46 | |             assert!(N == mem::size_of::<T::Type>());
+47 | |         }
+   | |_________^
+
+note: erroneous constant encountered
+  --> /git/monostate/src/string.rs:29:33
+   |
+29 |     const VALUE: &'static str = T::__private.0;
+   |                                 ^^^^^^^^^^^^
+
+note: erroneous constant encountered
+   --> /git/monostate/src/value.rs:132:37
+    |
+132 |     pub const VALUE: &'static str = V::VALUE;
+    |                                     ^^^^^^^^
+" "
+error[E0080]: evaluation panicked: assertion failed: N == mem::size_of::<T::Type>()
+ --> $WORKSPACE/src/string.rs
+  |
+  |             assert!(N == mem::size_of::<T::Type>());
+  |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ evaluation of `<(monostate::alphabet::len<8>, (monostate::alphabet::char<'a'>, monostate::alphabet::char<'s'>, monostate::alphabet::char<'d'>, monostate::alphabet::char<'f'>)) as monostate::string::Sealed>::__private::{constant#0}` failed here
+
+note: erroneous constant encountered
+  --> $WORKSPACE/src/string.rs
+   |
+   | /         const {
+   | |             assert!(N == mem::size_of::<T::Type>());
+   | |         }
+   | |_________^
+
+note: erroneous constant encountered
+  --> $WORKSPACE/src/string.rs
+   |
+   |     const VALUE: &'static str = T::__private.0;
+   |                                 ^^^^^^^^^^^^
+
+note: erroneous constant encountered
+   --> $WORKSPACE/src/value.rs
+    |
+    |     pub const VALUE: &'static str = V::VALUE;
+    |                                     ^^^^^^^^
+"}