Improve error message

2 files changed, 39 insertions, 6 deletions

diff --git a/tests/ui/impl-trait/normalize-tait-in-const.rs b/tests/ui/impl-trait/normalize-tait-in-const.rs
index fc90139d640..e3f53e5f8a8 100644
--- a/tests/ui/impl-trait/normalize-tait-in-const.rs
+++ b/tests/ui/impl-trait/normalize-tait-in-const.rs
@@ -24,7 +24,7 @@ mod foo {
 }
 use foo::*;
 
-const fn with_positive<F: ~const for<'a> Fn(&'a Alias<'a>) + ~const Destruct>(fun: F) {
+const fn with_positive<F: for<'a> ~const Fn(&'a Alias<'a>) + ~const Destruct>(fun: F) {
     fun(filter_positive());
 }
 
diff --git a/tests/ui/impl-trait/normalize-tait-in-const.stderr b/tests/ui/impl-trait/normalize-tait-in-const.stderr
index 77de689fb97..b20dabe7b25 100644
--- a/tests/ui/impl-trait/normalize-tait-in-const.stderr
+++ b/tests/ui/impl-trait/normalize-tait-in-const.stderr
@@ -1,8 +1,41 @@
-error: expected a trait, found type
-  --> $DIR/normalize-tait-in-const.rs:27:34
+error: `~const` can only be applied to `#[const_trait]` traits
+  --> $DIR/normalize-tait-in-const.rs:27:42
    |
-LL | const fn with_positive<F: ~const for<'a> Fn(&'a Alias<'a>) + ~const Destruct>(fun: F) {
-   |                                  ^^^^^^^^^^^^^^^^^^^^^^^^^
+LL | const fn with_positive<F: for<'a> ~const Fn(&'a Alias<'a>) + ~const Destruct>(fun: F) {
+   |                                          ^^^^^^^^^^^^^^^^^
 
-error: aborting due to 1 previous error
+error: `~const` can only be applied to `#[const_trait]` traits
+  --> $DIR/normalize-tait-in-const.rs:27:69
+   |
+LL | const fn with_positive<F: for<'a> ~const Fn(&'a Alias<'a>) + ~const Destruct>(fun: F) {
+   |                                                                     ^^^^^^^^
+
+error[E0015]: cannot call non-const closure in constant functions
+  --> $DIR/normalize-tait-in-const.rs:28:5
+   |
+LL |     fun(filter_positive());
+   |     ^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: calls in constant functions are limited to constant functions, tuple structs and tuple variants
+help: consider further restricting this bound
+   |
+LL | const fn with_positive<F: for<'a> ~const Fn(&'a Alias<'a>) + ~const Destruct + ~const Fn(&foo::Alias<'_>)>(fun: F) {
+   |                                                                              ++++++++++++++++++++++++++++
+help: add `#![feature(effects)]` to the crate attributes to enable
+   |
+LL + #![feature(effects)]
+   |
+
+error[E0493]: destructor of `F` cannot be evaluated at compile-time
+  --> $DIR/normalize-tait-in-const.rs:27:79
+   |
+LL | const fn with_positive<F: for<'a> ~const Fn(&'a Alias<'a>) + ~const Destruct>(fun: F) {
+   |                                                                               ^^^ the destructor for this type cannot be evaluated in constant functions
+LL |     fun(filter_positive());
+LL | }
+   | - value is dropped here
+
+error: aborting due to 4 previous errors
 
+Some errors have detailed explanations: E0015, E0493.
+For more information about an error, try `rustc --explain E0015`.