Unlock trailing where-clauses for lazy type aliases

6 files changed, 86 insertions, 2 deletions

diff --git a/tests/ui/lazy-type-alias/leading-where-clause.fixed b/tests/ui/lazy-type-alias/leading-where-clause.fixed
new file mode 100644
index 00000000000..07ebc09b30e
--- /dev/null
+++ b/tests/ui/lazy-type-alias/leading-where-clause.fixed
@@ -0,0 +1,15 @@
+// run-rustfix
+
+#![feature(lazy_type_alias)]
+#![allow(incomplete_features)]
+
+// Check that we *reject* leading where-clauses on lazy type aliases.
+
+type Alias<T>
+
+= T where String: From<T>;
+//~^^^ ERROR where clauses are not allowed before the type for type aliases
+
+fn main() {
+    let _: Alias<&str>;
+}
diff --git a/tests/ui/lazy-type-alias/leading-where-clause.rs b/tests/ui/lazy-type-alias/leading-where-clause.rs
new file mode 100644
index 00000000000..4a654293472
--- /dev/null
+++ b/tests/ui/lazy-type-alias/leading-where-clause.rs
@@ -0,0 +1,16 @@
+// run-rustfix
+
+#![feature(lazy_type_alias)]
+#![allow(incomplete_features)]
+
+// Check that we *reject* leading where-clauses on lazy type aliases.
+
+type Alias<T>
+where
+    String: From<T>,
+= T;
+//~^^^ ERROR where clauses are not allowed before the type for type aliases
+
+fn main() {
+    let _: Alias<&str>;
+}
diff --git a/tests/ui/lazy-type-alias/leading-where-clause.stderr b/tests/ui/lazy-type-alias/leading-where-clause.stderr
new file mode 100644
index 00000000000..8ddf0ce6c65
--- /dev/null
+++ b/tests/ui/lazy-type-alias/leading-where-clause.stderr
@@ -0,0 +1,16 @@
+error: where clauses are not allowed before the type for type aliases
+  --> $DIR/leading-where-clause.rs:9:1
+   |
+LL | / where
+LL | |     String: From<T>,
+   | |____________________^
+   |
+   = note: see issue #89122 <https://github.com/rust-lang/rust/issues/89122> for more information
+help: move it to the end of the type declaration
+   |
+LL + 
+LL ~ = T where String: From<T>;
+   |
+
+error: aborting due to previous error
+
diff --git a/tests/ui/lazy-type-alias/trailing-where-clause.rs b/tests/ui/lazy-type-alias/trailing-where-clause.rs
new file mode 100644
index 00000000000..ac9598fe5f6
--- /dev/null
+++ b/tests/ui/lazy-type-alias/trailing-where-clause.rs
@@ -0,0 +1,13 @@
+#![feature(lazy_type_alias)]
+#![allow(incomplete_features)]
+
+// Check that we allow & respect trailing where-clauses on lazy type aliases.
+
+type Alias<T> = T
+where
+    String: From<T>;
+
+fn main() {
+    let _: Alias<&str>;
+    let _: Alias<()>; //~ ERROR the trait bound `String: From<()>` is not satisfied
+}
diff --git a/tests/ui/lazy-type-alias/trailing-where-clause.stderr b/tests/ui/lazy-type-alias/trailing-where-clause.stderr
new file mode 100644
index 00000000000..d7606ba6b2a
--- /dev/null
+++ b/tests/ui/lazy-type-alias/trailing-where-clause.stderr
@@ -0,0 +1,22 @@
+error[E0277]: the trait bound `String: From<()>` is not satisfied
+  --> $DIR/trailing-where-clause.rs:12:12
+   |
+LL |     let _: Alias<()>;
+   |            ^^^^^^^^^ the trait `From<()>` is not implemented for `String`
+   |
+   = help: the following other types implement trait `From<T>`:
+             <String as From<char>>
+             <String as From<Box<str>>>
+             <String as From<Cow<'a, str>>>
+             <String as From<&str>>
+             <String as From<&mut str>>
+             <String as From<&String>>
+note: required by a bound on the type alias `Alias`
+  --> $DIR/trailing-where-clause.rs:8:13
+   |
+LL |     String: From<T>;
+   |             ^^^^^^^ required by this bound
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0277`.
diff --git a/tests/ui/where-clauses/where-clause-placement-type-alias.stderr b/tests/ui/where-clauses/where-clause-placement-type-alias.stderr
index b3c155a48dd..d341148b04c 100644
--- a/tests/ui/where-clauses/where-clause-placement-type-alias.stderr
+++ b/tests/ui/where-clauses/where-clause-placement-type-alias.stderr
@@ -4,7 +4,8 @@ error: where clauses are not allowed after the type for type aliases
 LL | type Bar = () where u32: Copy;
    |               ^^^^^^^^^^^^^^^
    |
-   = note: see issue #89122 <https://github.com/rust-lang/rust/issues/89122> for more information
+   = note: see issue #112792 <https://github.com/rust-lang/rust/issues/112792> for more information
+   = help: add `#![feature(lazy_type_alias)]` to the crate attributes to enable
 
 error: where clauses are not allowed after the type for type aliases
   --> $DIR/where-clause-placement-type-alias.rs:8:15
@@ -12,7 +13,8 @@ error: where clauses are not allowed after the type for type aliases
 LL | type Baz = () where;
    |               ^^^^^
    |
-   = note: see issue #89122 <https://github.com/rust-lang/rust/issues/89122> for more information
+   = note: see issue #112792 <https://github.com/rust-lang/rust/issues/112792> for more information
+   = help: add `#![feature(lazy_type_alias)]` to the crate attributes to enable
 
 error: aborting due to 2 previous errors