Add suggestion to remove if in let...else block

Adds an additional hint to failures where we encounter an else keyword
while we're parsing an if-let block.

This is likely that the user has accidentally mixed if-let and let...else
together.

2 files changed, 25 insertions, 0 deletions

diff --git a/tests/ui/let-else/accidental-if.rs b/tests/ui/let-else/accidental-if.rs
new file mode 100644
index 00000000000..3fba630435c
--- /dev/null
+++ b/tests/ui/let-else/accidental-if.rs
@@ -0,0 +1,6 @@
+fn main() {
+    let x = Some(123);
+    if let Some(y) = x else { //~ ERROR this `if` expression is missing a block
+        return;
+    };
+}
diff --git a/tests/ui/let-else/accidental-if.stderr b/tests/ui/let-else/accidental-if.stderr
new file mode 100644
index 00000000000..5474a67aac4
--- /dev/null
+++ b/tests/ui/let-else/accidental-if.stderr
@@ -0,0 +1,19 @@
+error: this `if` expression is missing a block after the condition
+  --> $DIR/accidental-if.rs:3:5
+   |
+LL |     if let Some(y) = x else {
+   |     ^^
+   |
+help: add a block here
+  --> $DIR/accidental-if.rs:3:23
+   |
+LL |     if let Some(y) = x else {
+   |                       ^
+help: remove the `if` if you meant to write a `let...else` statement
+  --> $DIR/accidental-if.rs:3:5
+   |
+LL |     if let Some(y) = x else {
+   |     ^^
+
+error: aborting due to previous error
+