Suggest `if let` on `let` refutable binding

13 files changed, 142 insertions, 0 deletions

diff --git a/src/test/ui/consts/const-match-check.eval1.stderr b/src/test/ui/consts/const-match-check.eval1.stderr
index 24d2e3ce539..087cc3c86a6 100644
--- a/src/test/ui/consts/const-match-check.eval1.stderr
+++ b/src/test/ui/consts/const-match-check.eval1.stderr
@@ -3,6 +3,13 @@ error[E0005]: refutable pattern in local binding: `std::i32::MIN..=-1i32` and `1
    |
 LL |     A = { let 0 = 0; 0 },
    |               ^ patterns `std::i32::MIN..=-1i32` and `1i32..=std::i32::MAX` 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
+help: you might want to use `if let` to ignore the variant that isn't matched
+   |
+LL |     A = { if let 0 = 0 { /* */ } 0 },
+   |           ^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/consts/const-match-check.eval2.stderr b/src/test/ui/consts/const-match-check.eval2.stderr
index 5d59d06f798..80d9f794bc1 100644
--- a/src/test/ui/consts/const-match-check.eval2.stderr
+++ b/src/test/ui/consts/const-match-check.eval2.stderr
@@ -3,6 +3,13 @@ error[E0005]: refutable pattern in local binding: `std::i32::MIN..=-1i32` and `1
    |
 LL |     let x: [i32; { let 0 = 0; 0 }] = [];
    |                        ^ patterns `std::i32::MIN..=-1i32` and `1i32..=std::i32::MAX` 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
+help: you might want to use `if let` to ignore the variant that isn't matched
+   |
+LL |     let x: [i32; { if let 0 = 0 { /* */ } 0 }] = [];
+   |                    ^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/consts/const-match-check.matchck.stderr b/src/test/ui/consts/const-match-check.matchck.stderr
index 6d74c26f9f7..e6b2f212bb4 100644
--- a/src/test/ui/consts/const-match-check.matchck.stderr
+++ b/src/test/ui/consts/const-match-check.matchck.stderr
@@ -3,24 +3,52 @@ error[E0005]: refutable pattern in local binding: `std::i32::MIN..=-1i32` and `1
    |
 LL | const X: i32 = { let 0 = 0; 0 };
    |                      ^ patterns `std::i32::MIN..=-1i32` and `1i32..=std::i32::MAX` 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
+help: you might want to use `if let` to ignore the variant that isn't matched
+   |
+LL | const X: i32 = { if let 0 = 0 { /* */ } 0 };
+   |                  ^^^^^^^^^^^^^^^^^^^^^^
 
 error[E0005]: refutable pattern in local binding: `std::i32::MIN..=-1i32` and `1i32..=std::i32::MAX` not covered
   --> $DIR/const-match-check.rs:8:23
    |
 LL | static Y: i32 = { let 0 = 0; 0 };
    |                       ^ patterns `std::i32::MIN..=-1i32` and `1i32..=std::i32::MAX` 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
+help: you might want to use `if let` to ignore the variant that isn't matched
+   |
+LL | static Y: i32 = { if let 0 = 0 { /* */ } 0 };
+   |                   ^^^^^^^^^^^^^^^^^^^^^^
 
 error[E0005]: refutable pattern in local binding: `std::i32::MIN..=-1i32` and `1i32..=std::i32::MAX` not covered
   --> $DIR/const-match-check.rs:13:26
    |
 LL |     const X: i32 = { let 0 = 0; 0 };
    |                          ^ patterns `std::i32::MIN..=-1i32` and `1i32..=std::i32::MAX` 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
+help: you might want to use `if let` to ignore the variant that isn't matched
+   |
+LL |     const X: i32 = { if let 0 = 0 { /* */ } 0 };
+   |                      ^^^^^^^^^^^^^^^^^^^^^^
 
 error[E0005]: refutable pattern in local binding: `std::i32::MIN..=-1i32` and `1i32..=std::i32::MAX` not covered
   --> $DIR/const-match-check.rs:19:26
    |
 LL |     const X: i32 = { let 0 = 0; 0 };
    |                          ^ patterns `std::i32::MIN..=-1i32` and `1i32..=std::i32::MAX` 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
+help: you might want to use `if let` to ignore the variant that isn't matched
+   |
+LL |     const X: i32 = { if let 0 = 0 { /* */ } 0 };
+   |                      ^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to 4 previous errors
 
diff --git a/src/test/ui/empty/empty-never-array.stderr b/src/test/ui/empty/empty-never-array.stderr
index 7d59d553d88..d865b59f0b9 100644
--- a/src/test/ui/empty/empty-never-array.stderr
+++ b/src/test/ui/empty/empty-never-array.stderr
@@ -11,6 +11,13 @@ LL | | }
 ...
 LL |       let Helper::U(u) = Helper::T(t, []);
    |           ^^^^^^^^^^^^ pattern `T(_, _)` 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
+help: you might want to use `if let` to ignore the variant that isn't matched
+   |
+LL |     if let Helper::U(u) = Helper::T(t, []) { /* */ }
+   |
 
 error[E0381]: use of possibly-uninitialized variable: `u`
   --> $DIR/empty-never-array.rs:12:5
diff --git a/src/test/ui/error-codes/E0005.stderr b/src/test/ui/error-codes/E0005.stderr
index 56a4bcffc81..577c6e886d5 100644
--- a/src/test/ui/error-codes/E0005.stderr
+++ b/src/test/ui/error-codes/E0005.stderr
@@ -3,6 +3,13 @@ error[E0005]: refutable pattern in local binding: `None` not covered
    |
 LL |     let Some(y) = 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
+help: you might want to use `if let` to ignore the variant that isn't matched
+   |
+LL |     if let Some(y) = x { /* */ }
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/feature-gates/feature-gate-exhaustive-patterns.nll.stderr b/src/test/ui/feature-gates/feature-gate-exhaustive-patterns.nll.stderr
new file mode 100644
index 00000000000..d77fbc1e823
--- /dev/null
+++ b/src/test/ui/feature-gates/feature-gate-exhaustive-patterns.nll.stderr
@@ -0,0 +1,16 @@
+error[E0005]: refutable pattern in local binding: `Err(_)` not covered
+  --> $DIR/feature-gate-exhaustive-patterns.rs:7:9
+   |
+LL |     let Ok(_x) = foo();
+   |         ^^^^^^ pattern `Err(_)` 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
+help: you might want to use `if let` to ignore the variant that isn't matched
+   |
+LL |     if let Ok(_x) = foo() { /* */ }
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0005`.
diff --git a/src/test/ui/feature-gates/feature-gate-exhaustive-patterns.stderr b/src/test/ui/feature-gates/feature-gate-exhaustive-patterns.stderr
index dd4ca1f67e3..d77fbc1e823 100644
--- a/src/test/ui/feature-gates/feature-gate-exhaustive-patterns.stderr
+++ b/src/test/ui/feature-gates/feature-gate-exhaustive-patterns.stderr
@@ -3,6 +3,13 @@ error[E0005]: refutable pattern in local binding: `Err(_)` not covered
    |
 LL |     let Ok(_x) = foo();
    |         ^^^^^^ pattern `Err(_)` 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
+help: you might want to use `if let` to ignore the variant that isn't matched
+   |
+LL |     if let Ok(_x) = foo() { /* */ }
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/issues/issue-31561.stderr b/src/test/ui/issues/issue-31561.stderr
index 9ec26b024bc..d3c8e876b8a 100644
--- a/src/test/ui/issues/issue-31561.stderr
+++ b/src/test/ui/issues/issue-31561.stderr
@@ -12,6 +12,13 @@ LL | | }
 ...
 LL |       let Thing::Foo(y) = Thing::Foo(1);
    |           ^^^^^^^^^^^^^ patterns `Bar` and `Baz` 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
+help: you might want to use `if let` to ignore the variant that isn't matched
+   |
+LL |     if let Thing::Foo(y) = Thing::Foo(1) { /* */ }
+   |
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/match/non-exhaustive-defined-here.stderr b/src/test/ui/match/non-exhaustive-defined-here.stderr
index 25b8bbdab2d..e5f01174ac1 100644
--- a/src/test/ui/match/non-exhaustive-defined-here.stderr
+++ b/src/test/ui/match/non-exhaustive-defined-here.stderr
@@ -41,6 +41,13 @@ LL | | }
 ...
 LL |       let E::A = e;
    |           ^^^^ patterns `B` and `C` 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
+help: you might want to use `if let` to ignore the variant that isn't matched
+   |
+LL |     if let E::A = e { /* */ }
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error[E0004]: non-exhaustive patterns: `&B` and `&C` not covered
   --> $DIR/non-exhaustive-defined-here.rs:40:11
@@ -85,6 +92,13 @@ LL | | }
 ...
 LL |       let E::A = e;
    |           ^^^^ patterns `&B` and `&C` 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
+help: you might want to use `if let` to ignore the variant that isn't matched
+   |
+LL |     if let E::A = e { /* */ }
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error[E0004]: non-exhaustive patterns: `&&mut &B` and `&&mut &C` not covered
   --> $DIR/non-exhaustive-defined-here.rs:48:11
@@ -129,6 +143,13 @@ LL | | }
 ...
 LL |       let E::A = e;
    |           ^^^^ patterns `&&mut &B` and `&&mut &C` 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
+help: you might want to use `if let` to ignore the variant that isn't matched
+   |
+LL |     if let E::A = e { /* */ }
+   |
 
 error[E0004]: non-exhaustive patterns: `None` not covered
   --> $DIR/non-exhaustive-defined-here.rs:65:11
@@ -163,6 +184,13 @@ LL | | }
 ...
 LL |       let Opt::Some(ref _x) = e;
    |           ^^^^^^^^^^^^^^^^^ 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
+help: you might want to use `if let` to ignore the variant that isn't matched
+   |
+LL |     if let Opt::Some(ref _x) = e { /* */ }
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to 8 previous errors
 
diff --git a/src/test/ui/recursion/recursive-types-are-not-uninhabited.stderr b/src/test/ui/recursion/recursive-types-are-not-uninhabited.stderr
index b9385952faf..f9ae75b1831 100644
--- a/src/test/ui/recursion/recursive-types-are-not-uninhabited.stderr
+++ b/src/test/ui/recursion/recursive-types-are-not-uninhabited.stderr
@@ -3,6 +3,13 @@ error[E0005]: refutable pattern in local binding: `Err(_)` not covered
    |
 LL |     let Ok(x) = res;
    |         ^^^^^ pattern `Err(_)` 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
+help: you might want to use `if let` to ignore the variant that isn't matched
+   |
+LL |     if let Ok(x) = res { /* */ }
+   |
 
 error[E0381]: use of possibly-uninitialized variable: `x`
   --> $DIR/recursive-types-are-not-uninhabited.rs:8:5
diff --git a/src/test/ui/refutable-pattern-errors.stderr b/src/test/ui/refutable-pattern-errors.stderr
index 3b13e25293d..0cf5d9cd5f1 100644
--- a/src/test/ui/refutable-pattern-errors.stderr
+++ b/src/test/ui/refutable-pattern-errors.stderr
@@ -9,6 +9,13 @@ error[E0005]: refutable pattern in local binding: `(std::i32::MIN..=0i32, _)` an
    |
 LL |     let (1, (Some(1), 2..=3)) = (1, (None, 2));
    |         ^^^^^^^^^^^^^^^^^^^^^ patterns `(std::i32::MIN..=0i32, _)` and `(2i32..=std::i32::MAX, _)` 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
+help: you might want to use `if let` to ignore the variant that isn't matched
+   |
+LL |     if let (1, (Some(1), 2..=3)) = (1, (None, 2)) { /* */ }
+   |
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/uninhabited/uninhabited-irrefutable.stderr b/src/test/ui/uninhabited/uninhabited-irrefutable.stderr
index 29ff1dc3760..26e1be34ea7 100644
--- a/src/test/ui/uninhabited/uninhabited-irrefutable.stderr
+++ b/src/test/ui/uninhabited/uninhabited-irrefutable.stderr
@@ -12,6 +12,13 @@ LL | | }
 ...
 LL |       let Foo::D(_y) = x;
    |           ^^^^^^^^^^ pattern `A(_)` 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
+help: you might want to use `if let` to ignore the variant that isn't matched
+   |
+LL |     if let Foo::D(_y) = x { /* */ }
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/uninhabited/uninhabited-matches-feature-gated.stderr b/src/test/ui/uninhabited/uninhabited-matches-feature-gated.stderr
index 25519ab2d6a..a49344e45ce 100644
--- a/src/test/ui/uninhabited/uninhabited-matches-feature-gated.stderr
+++ b/src/test/ui/uninhabited/uninhabited-matches-feature-gated.stderr
@@ -51,6 +51,13 @@ error[E0005]: refutable pattern in local binding: `Err(_)` not covered
    |
 LL |     let Ok(x) = x;
    |         ^^^^^ pattern `Err(_)` 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
+help: you might want to use `if let` to ignore the variant that isn't matched
+   |
+LL |     if let Ok(x) = x { /* */ }
+   |
 
 error: aborting due to 7 previous errors