Add regression test for rust-lang#94176

Author: est31

src/test/ui/let-else/issue-94176.rs

@@ -0,0 +1,10 @@
+// Issue #94176: wrong span for the error message of a mismatched type error,
+// if the function uses a `let else` construct.
+#![feature(let_else)]
+
+pub fn test(a: Option<u32>) -> Option<u32> { //~ ERROR mismatched types
+    let Some(_) = a else { return None; };
+    println!("Foo");
+}
+
+fn main() {}

src/test/ui/let-else/issue-94176.stderr

@@ -0,0 +1,19 @@
+error[E0308]: mismatched types
+  --> $DIR/issue-94176.rs:5:32
+   |
+LL | pub fn test(a: Option<u32>) -> Option<u32> {
+   |        ----                    ^^^^^^^^^^^ expected enum `Option`, found `()`
+   |        |
+   |        implicitly returns `()` as its body has no tail or `return` expression
+   |
+   = note:   expected enum `Option<u32>`
+           found unit type `()`
+help: consider returning the local binding `a`
+   |
+LL ~     println!("Foo");
+LL +     a
+   |
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0308`.