Provide suggestion on missing `let` in binding statement

Fix #78907.

3 files changed, 26 insertions, 0 deletions

diff --git a/src/test/ui/type/missing-let-in-binding.fixed b/src/test/ui/type/missing-let-in-binding.fixed
new file mode 100644
index 00000000000..d1787688950
--- /dev/null
+++ b/src/test/ui/type/missing-let-in-binding.fixed
@@ -0,0 +1,5 @@
+// run-rustfix
+fn main() {
+    let mut _foo: i32 = 1;
+    let _foo: i32 = 4; //~ ERROR type ascription is experimental
+}
diff --git a/src/test/ui/type/missing-let-in-binding.rs b/src/test/ui/type/missing-let-in-binding.rs
new file mode 100644
index 00000000000..ca42f2e6eac
--- /dev/null
+++ b/src/test/ui/type/missing-let-in-binding.rs
@@ -0,0 +1,5 @@
+// run-rustfix
+fn main() {
+    let mut _foo: i32 = 1;
+    _foo: i32 = 4; //~ ERROR type ascription is experimental
+}
diff --git a/src/test/ui/type/missing-let-in-binding.stderr b/src/test/ui/type/missing-let-in-binding.stderr
new file mode 100644
index 00000000000..12759c5096e
--- /dev/null
+++ b/src/test/ui/type/missing-let-in-binding.stderr
@@ -0,0 +1,16 @@
+error[E0658]: type ascription is experimental
+  --> $DIR/missing-let-in-binding.rs:4:5
+   |
+LL |     _foo: i32 = 4;
+   |     ^^^^^^^^^
+   |
+   = note: see issue #23416 <https://github.com/rust-lang/rust/issues/23416> for more information
+   = help: add `#![feature(type_ascription)]` to the crate attributes to enable
+help: you might have meant to introduce a new binding
+   |
+LL |     let _foo: i32 = 4;
+   |     +++
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0658`.