Suppress erroneous suggestion

The suggestion to use `let else` with an uninitialized refutable `let`
statement was erroneous: `let else` cannot be used with deferred
initialization.

compiler/rustc_mir_build/src/thir/pattern/check_match.rs

@@ -674,6 +674,7 @@ impl<'p, 'tcx> MatchVisitor<'p, 'tcx> {
         if let Some(span) = sp
             && self.tcx.sess.source_map().is_span_accessible(span)
             && interpreted_as_const.is_none()
+            && scrut.is_some()
         {
             let mut bindings = vec![];
             pat.each_binding(|name, _, _, _| bindings.push(name));

tests/ui/half-open-range-patterns/half-open-range-pats-inclusive-dotdotdot-bad-syntax.stderr

@@ -46,10 +46,6 @@ LL |     mac!(0);
    = note: for more information, visit https://doc.rust-lang.org/book/ch18-02-refutability.html
    = note: the matched value is of type `i32`
    = note: this error originates in the macro `mac` (in Nightly builds, run with -Z macro-backtrace for more info)
-help: you might want to use `if let` to ignore the variant that isn't matched
-   |
-LL |             if let ...$e; { todo!() }
-   |             ++            +++++++++++
 
 error: aborting due to 6 previous errors
 

tests/ui/half-open-range-patterns/half-open-range-pats-inclusive-no-end.stderr

@@ -67,10 +67,6 @@ LL |     mac!(0);
    = note: for more information, visit https://doc.rust-lang.org/book/ch18-02-refutability.html
    = note: the matched value is of type `i32`
    = note: this error originates in the macro `mac` (in Nightly builds, run with -Z macro-backtrace for more info)
-help: you might want to use `if let` to ignore the variant that isn't matched
-   |
-LL |             if let $e...; { todo!() }
-   |             ++            +++++++++++
 
 error[E0005]: refutable pattern in local binding
   --> $DIR/half-open-range-pats-inclusive-no-end.rs:20:17
@@ -85,10 +81,6 @@ LL |     mac!(0);
    = note: for more information, visit https://doc.rust-lang.org/book/ch18-02-refutability.html
    = note: the matched value is of type `i32`
    = note: this error originates in the macro `mac` (in Nightly builds, run with -Z macro-backtrace for more info)
-help: you might want to use `if let` to ignore the variant that isn't matched
-   |
-LL |             if let $e..=; { todo!() }
-   |             ++            +++++++++++
 
 error: aborting due to 8 previous errors
 

tests/ui/let-else/uninitialized-refutable-let-issue-123844.rs

@@ -0,0 +1,8 @@
+// https://github.com/rust-lang/rust/issues/123844
+// An uninitialized refutable let should not suggest `let else`, as it can't be used with deferred
+// initialization.
+
+fn main() {
+    let Some(x); //~ ERROR refutable pattern in local binding
+    x = 1;
+}

tests/ui/let-else/uninitialized-refutable-let-issue-123844.stderr

@@ -0,0 +1,13 @@
+error[E0005]: refutable pattern in local binding
+  --> $DIR/uninitialized-refutable-let-issue-123844.rs:6:9
+   |
+LL |     let Some(x);
+   |         ^^^^^^^ pattern `None` not covered
+   |
+   = note: `let` bindings require an "irrefutable pattern", like a `struct` or an `enum` with only one variant
+   = note: for more information, visit https://doc.rust-lang.org/book/ch18-02-refutability.html
+   = note: the matched value is of type `Option<i32>`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0005`.

tests/ui/parser/recover/recover-range-pats.stderr

@@ -491,10 +491,6 @@ LL |     mac2!(0, 1);
    = note: for more information, visit https://doc.rust-lang.org/book/ch18-02-refutability.html
    = note: the matched value is of type `i32`
    = note: this error originates in the macro `mac2` (in Nightly builds, run with -Z macro-backtrace for more info)
-help: you might want to use `if let` to ignore the variants that aren't matched
-   |
-LL |             if let $e1..$e2; { todo!() }
-   |             ++               +++++++++++
 
 error[E0005]: refutable pattern in local binding
   --> $DIR/recover-range-pats.rs:138:17
@@ -509,10 +505,6 @@ LL |     mac2!(0, 1);
    = note: for more information, visit https://doc.rust-lang.org/book/ch18-02-refutability.html
    = note: the matched value is of type `i32`
    = note: this error originates in the macro `mac2` (in Nightly builds, run with -Z macro-backtrace for more info)
-help: you might want to use `if let` to ignore the variants that aren't matched
-   |
-LL |             if let $e1...$e2; { todo!() }
-   |             ++                +++++++++++
 
 error[E0005]: refutable pattern in local binding
   --> $DIR/recover-range-pats.rs:142:17
@@ -527,10 +519,6 @@ LL |     mac2!(0, 1);
    = note: for more information, visit https://doc.rust-lang.org/book/ch18-02-refutability.html
    = note: the matched value is of type `i32`
    = note: this error originates in the macro `mac2` (in Nightly builds, run with -Z macro-backtrace for more info)
-help: you might want to use `if let` to ignore the variants that aren't matched
-   |
-LL |             if let $e1..=$e2; { todo!() }
-   |             ++                +++++++++++
 
 error[E0005]: refutable pattern in local binding
   --> $DIR/recover-range-pats.rs:151:17
@@ -545,10 +533,6 @@ LL |     mac!(0);
    = note: for more information, visit https://doc.rust-lang.org/book/ch18-02-refutability.html
    = note: the matched value is of type `i32`
    = note: this error originates in the macro `mac` (in Nightly builds, run with -Z macro-backtrace for more info)
-help: you might want to use `if let` to ignore the variant that isn't matched
-   |
-LL |             if let ..$e; { todo!() }
-   |             ++           +++++++++++
 
 error[E0005]: refutable pattern in local binding
   --> $DIR/recover-range-pats.rs:153:17
@@ -563,10 +547,6 @@ LL |     mac!(0);
    = note: for more information, visit https://doc.rust-lang.org/book/ch18-02-refutability.html
    = note: the matched value is of type `i32`
    = note: this error originates in the macro `mac` (in Nightly builds, run with -Z macro-backtrace for more info)
-help: you might want to use `if let` to ignore the variant that isn't matched
-   |
-LL |             if let ...$e; { todo!() }
-   |             ++            +++++++++++
 
 error[E0005]: refutable pattern in local binding
   --> $DIR/recover-range-pats.rs:156:17
@@ -581,10 +561,6 @@ LL |     mac!(0);
    = note: for more information, visit https://doc.rust-lang.org/book/ch18-02-refutability.html
    = note: the matched value is of type `i32`
    = note: this error originates in the macro `mac` (in Nightly builds, run with -Z macro-backtrace for more info)
-help: you might want to use `if let` to ignore the variant that isn't matched
-   |
-LL |             if let ..=$e; { todo!() }
-   |             ++            +++++++++++
 
 error[E0005]: refutable pattern in local binding
   --> $DIR/recover-range-pats.rs:158:17
@@ -599,10 +575,6 @@ LL |     mac!(0);
    = note: for more information, visit https://doc.rust-lang.org/book/ch18-02-refutability.html
    = note: the matched value is of type `i32`
    = note: this error originates in the macro `mac` (in Nightly builds, run with -Z macro-backtrace for more info)
-help: you might want to use `if let` to ignore the variant that isn't matched
-   |
-LL |             if let $e..; { todo!() }
-   |             ++           +++++++++++
 
 error[E0005]: refutable pattern in local binding
   --> $DIR/recover-range-pats.rs:160:17
@@ -617,10 +589,6 @@ LL |     mac!(0);
    = note: for more information, visit https://doc.rust-lang.org/book/ch18-02-refutability.html
    = note: the matched value is of type `i32`
    = note: this error originates in the macro `mac` (in Nightly builds, run with -Z macro-backtrace for more info)
-help: you might want to use `if let` to ignore the variant that isn't matched
-   |
-LL |             if let $e...; { todo!() }
-   |             ++            +++++++++++
 
 error[E0005]: refutable pattern in local binding
   --> $DIR/recover-range-pats.rs:162:17
@@ -635,10 +603,6 @@ LL |     mac!(0);
    = note: for more information, visit https://doc.rust-lang.org/book/ch18-02-refutability.html
    = note: the matched value is of type `i32`
    = note: this error originates in the macro `mac` (in Nightly builds, run with -Z macro-backtrace for more info)
-help: you might want to use `if let` to ignore the variant that isn't matched
-   |
-LL |             if let $e..=; { todo!() }
-   |             ++            +++++++++++
 
 error: aborting due to 69 previous errors