Visit patterns in THIR let expressions

matthewjasper · matthewjasper · commit 868de8e76bbc · 2023-11-06T16:23:09.000Z
This fixes some THIR unsafety checking errors not being emitted for
let expressions in these situations.
diff --git a/compiler/rustc_middle/src/thir/visit.rs b/compiler/rustc_middle/src/thir/visit.rs
@@ -66,8 +66,9 @@ pub fn walk_expr<'a, 'tcx: 'a, V: Visitor<'a, 'tcx>>(visitor: &mut V, expr: &Exp
         Use { source } => visitor.visit_expr(&visitor.thir()[source]),
         NeverToAny { source } => visitor.visit_expr(&visitor.thir()[source]),
         PointerCoercion { source, cast: _ } => visitor.visit_expr(&visitor.thir()[source]),
-        Let { expr, .. } => {
+        Let { expr, ref pat } => {
             visitor.visit_expr(&visitor.thir()[expr]);
+            visitor.visit_pat(pat);
         }
         Loop { body } => visitor.visit_expr(&visitor.thir()[body]),
         Match { scrutinee, ref arms, .. } => {
diff --git a/compiler/rustc_mir_build/src/check_unsafety.rs b/compiler/rustc_mir_build/src/check_unsafety.rs
@@ -495,14 +495,6 @@ impl<'a, 'tcx> Visitor<'a, 'tcx> for UnsafetyVisitor<'a, 'tcx> {
                     }
                 }
             }
-            ExprKind::Let { expr: expr_id, .. } => {
-                let let_expr = &self.thir[expr_id];
-                if let ty::Adt(adt_def, _) = let_expr.ty.kind()
-                    && adt_def.is_union()
-                {
-                    self.requires_unsafe(expr.span, AccessToUnionField);
-                }
-            }
             _ => {}
         }
         visit::walk_expr(self, expr);
diff --git a/tests/ui/union/union-unsafe.mir.stderr b/tests/ui/union/union-unsafe.mir.stderr
@@ -1,75 +1,83 @@
 error[E0133]: access to union field is unsafe and requires unsafe function or block
-  --> $DIR/union-unsafe.rs:33:5
+  --> $DIR/union-unsafe.rs:34:5
    |
 LL |     *(u.p) = 13;
    |     ^^^^^^^^^^^ access to union field
    |
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
 error[E0133]: access to union field is unsafe and requires unsafe function or block
-  --> $DIR/union-unsafe.rs:46:6
+  --> $DIR/union-unsafe.rs:47:6
    |
 LL |     *u3.a = T::default();
    |      ^^^^ access to union field
    |
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
 error[E0133]: access to union field is unsafe and requires unsafe function or block
-  --> $DIR/union-unsafe.rs:52:6
+  --> $DIR/union-unsafe.rs:53:6
    |
 LL |     *u3.a = T::default();
    |      ^^^^ access to union field
    |
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
 error[E0133]: access to union field is unsafe and requires unsafe function or block
-  --> $DIR/union-unsafe.rs:60:13
+  --> $DIR/union-unsafe.rs:61:13
    |
 LL |     let a = u1.a;
    |             ^^^^ access to union field
    |
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
 error[E0133]: access to union field is unsafe and requires unsafe function or block
-  --> $DIR/union-unsafe.rs:63:14
+  --> $DIR/union-unsafe.rs:64:14
    |
 LL |     let U1 { a } = u1;
    |              ^ access to union field
    |
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
 error[E0133]: access to union field is unsafe and requires unsafe function or block
-  --> $DIR/union-unsafe.rs:64:12
+  --> $DIR/union-unsafe.rs:65:12
    |
 LL |     if let U1 { a: 12 } = u1 {}
    |            ^^^^^^^^^^^^ access to union field
    |
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
 error[E0133]: access to union field is unsafe and requires unsafe function or block
-  --> $DIR/union-unsafe.rs:69:6
+  --> $DIR/union-unsafe.rs:66:12
+   |
+LL |     if let Some(U1 { a: 13 }) = Some(u1) {}
+   |            ^^^^^^^^^^^^^^^^^^ access to union field
+   |
+   = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
+
+error[E0133]: access to union field is unsafe and requires unsafe function or block
+  --> $DIR/union-unsafe.rs:71:6
    |
 LL |     *u2.a = String::from("new");
    |      ^^^^ access to union field
    |
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
 error[E0133]: access to union field is unsafe and requires unsafe function or block
-  --> $DIR/union-unsafe.rs:73:6
+  --> $DIR/union-unsafe.rs:75:6
    |
 LL |     *u3.a = 1;
    |      ^^^^ access to union field
    |
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
 error[E0133]: access to union field is unsafe and requires unsafe function or block
-  --> $DIR/union-unsafe.rs:77:6
+  --> $DIR/union-unsafe.rs:79:6
    |
 LL |     *u3.a = String::from("new");
    |      ^^^^ access to union field
    |
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
-error: aborting due to 9 previous errors
+error: aborting due to 10 previous errors
 
 For more information about this error, try `rustc --explain E0133`.
diff --git a/tests/ui/union/union-unsafe.rs b/tests/ui/union/union-unsafe.rs
@@ -1,30 +1,31 @@
 // revisions: mir thir
 // [thir]compile-flags: -Z thir-unsafeck
 
-use std::mem::ManuallyDrop;
 use std::cell::RefCell;
+use std::mem::ManuallyDrop;
 
 union U1 {
-    a: u8
+    a: u8,
 }
 
 union U2 {
-    a: ManuallyDrop<String>
+    a: ManuallyDrop<String>,
 }
 
 union U3<T> {
-    a: ManuallyDrop<T>
+    a: ManuallyDrop<T>,
 }
 
 union U4<T: Copy> {
-    a: T
+    a: T,
 }
 
 union URef {
     p: &'static mut i32,
 }
 
-union URefCell { // field that does not drop but is not `Copy`, either
+union URefCell {
+    // field that does not drop but is not `Copy`, either
     a: (ManuallyDrop<RefCell<i32>>, i32),
 }
 
@@ -62,6 +63,7 @@ fn main() {
 
     let U1 { a } = u1; //~ ERROR access to union field is unsafe
     if let U1 { a: 12 } = u1 {} //~ ERROR access to union field is unsafe
+    if let Some(U1 { a: 13 }) = Some(u1) {} //~ ERROR access to union field is unsafe
     // let U1 { .. } = u1; // OK
 
     let mut u2 = U2 { a: ManuallyDrop::new(String::from("old")) }; // OK
diff --git a/tests/ui/union/union-unsafe.thir.stderr b/tests/ui/union/union-unsafe.thir.stderr
@@ -1,75 +1,83 @@
 error[E0133]: access to union field is unsafe and requires unsafe function or block
-  --> $DIR/union-unsafe.rs:33:6
+  --> $DIR/union-unsafe.rs:34:6
    |
 LL |     *(u.p) = 13;
    |      ^^^^^ access to union field
    |
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
 error[E0133]: access to union field is unsafe and requires unsafe function or block
-  --> $DIR/union-unsafe.rs:46:6
+  --> $DIR/union-unsafe.rs:47:6
    |
 LL |     *u3.a = T::default();
    |      ^^^^ access to union field
    |
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
 error[E0133]: access to union field is unsafe and requires unsafe function or block
-  --> $DIR/union-unsafe.rs:52:6
+  --> $DIR/union-unsafe.rs:53:6
    |
 LL |     *u3.a = T::default();
    |      ^^^^ access to union field
    |
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
 error[E0133]: access to union field is unsafe and requires unsafe function or block
-  --> $DIR/union-unsafe.rs:60:13
+  --> $DIR/union-unsafe.rs:61:13
    |
 LL |     let a = u1.a;
    |             ^^^^ access to union field
    |
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
 error[E0133]: access to union field is unsafe and requires unsafe function or block
-  --> $DIR/union-unsafe.rs:63:14
+  --> $DIR/union-unsafe.rs:64:14
    |
 LL |     let U1 { a } = u1;
    |              ^ access to union field
    |
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
 error[E0133]: access to union field is unsafe and requires unsafe function or block
-  --> $DIR/union-unsafe.rs:64:8
+  --> $DIR/union-unsafe.rs:65:20
    |
 LL |     if let U1 { a: 12 } = u1 {}
-   |        ^^^^^^^^^^^^^^^^^^^^^ access to union field
+   |                    ^^ access to union field
    |
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
 error[E0133]: access to union field is unsafe and requires unsafe function or block
-  --> $DIR/union-unsafe.rs:69:6
+  --> $DIR/union-unsafe.rs:66:25
+   |
+LL |     if let Some(U1 { a: 13 }) = Some(u1) {}
+   |                         ^^ access to union field
+   |
+   = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
+
+error[E0133]: access to union field is unsafe and requires unsafe function or block
+  --> $DIR/union-unsafe.rs:71:6
    |
 LL |     *u2.a = String::from("new");
    |      ^^^^ access to union field
    |
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
 error[E0133]: access to union field is unsafe and requires unsafe function or block
-  --> $DIR/union-unsafe.rs:73:6
+  --> $DIR/union-unsafe.rs:75:6
    |
 LL |     *u3.a = 1;
    |      ^^^^ access to union field
    |
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
 error[E0133]: access to union field is unsafe and requires unsafe function or block
-  --> $DIR/union-unsafe.rs:77:6
+  --> $DIR/union-unsafe.rs:79:6
    |
 LL |     *u3.a = String::from("new");
    |      ^^^^ access to union field
    |
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
-error: aborting due to 9 previous errors
+error: aborting due to 10 previous errors
 
 For more information about this error, try `rustc --explain E0133`.
diff --git a/tests/ui/unsafe/ranged_ints2.mirunsafeck.stderr b/tests/ui/unsafe/ranged_ints2.mirunsafeck.stderr
@@ -6,6 +6,14 @@ LL |     let y = &mut x.0;
    |
    = note: mutating layout constrained fields cannot statically be checked for valid values
 
-error: aborting due to previous error
+error[E0133]: mutation of layout constrained field is unsafe and requires unsafe function or block
+  --> $DIR/ranged_ints2.rs:12:25
+   |
+LL |     if let Some(NonZero(ref mut y)) = Some(x) {}
+   |                         ^^^^^^^^^ mutation of layout constrained field
+   |
+   = note: mutating layout constrained fields cannot statically be checked for valid values
+
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0133`.
diff --git a/tests/ui/unsafe/ranged_ints2.rs b/tests/ui/unsafe/ranged_ints2.rs
@@ -9,4 +9,5 @@ pub(crate) struct NonZero<T>(pub(crate) T);
 fn main() {
     let mut x = unsafe { NonZero(1) };
     let y = &mut x.0; //~ ERROR mutation of layout constrained field is unsafe
+    if let Some(NonZero(ref mut y)) = Some(x) {} //~ ERROR mutation of layout constrained field is unsafe
 }
diff --git a/tests/ui/unsafe/ranged_ints2.thirunsafeck.stderr b/tests/ui/unsafe/ranged_ints2.thirunsafeck.stderr
@@ -6,6 +6,14 @@ LL |     let y = &mut x.0;
    |
    = note: mutating layout constrained fields cannot statically be checked for valid values
 
-error: aborting due to previous error
+error[E0133]: mutation of layout constrained field is unsafe and requires unsafe function or block
+  --> $DIR/ranged_ints2.rs:12:25
+   |
+LL |     if let Some(NonZero(ref mut y)) = Some(x) {}
+   |                         ^^^^^^^^^ mutation of layout constrained field
+   |
+   = note: mutating layout constrained fields cannot statically be checked for valid values
+
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0133`.

Original file line number	Diff line number	Diff line change
`@@ -495,14 +495,6 @@ impl<'a, 'tcx> Visitor<'a, 'tcx> for UnsafetyVisitor<'a, 'tcx> {`
`495`	`495`	`}`
`496`	`496`	`}`
`497`	`497`	`}`
`498`		`- ExprKind::Let { expr: expr_id, .. } => {`
`499`		`- let let_expr = &self.thir[expr_id];`
`500`		`- if let ty::Adt(adt_def, _) = let_expr.ty.kind()`
`501`		`- && adt_def.is_union()`
`502`		`- {`
`503`		`- self.requires_unsafe(expr.span, AccessToUnionField);`
`504`		`- }`
`505`		`- }`
`506`	`498`	`_ => {}`
`507`	`499`	`}`
`508`	`500`	`visit::walk_expr(self, expr);`
Original file line number	Diff line number	Diff line change
`@@ -1,75 +1,83 @@`
`1`	`1`	`error[E0133]: access to union field is unsafe and requires unsafe function or block`
`2`		`- --> $DIR/union-unsafe.rs:33:5`
	`2`	`+ --> $DIR/union-unsafe.rs:34:5`
`3`	`3`	`\|`
`4`	`4`	`LL \| *(u.p) = 13;`
`5`	`5`	`\| ^^^^^^^^^^^ access to union field`
`6`	`6`	`\|`
`7`	`7`	`= note: the field may not be properly initialized: using uninitialized data will cause undefined behavior`
`8`	`8`
`9`	`9`	`error[E0133]: access to union field is unsafe and requires unsafe function or block`
`10`		`- --> $DIR/union-unsafe.rs:46:6`
	`10`	`+ --> $DIR/union-unsafe.rs:47:6`
`11`	`11`	`\|`
`12`	`12`	`LL \| *u3.a = T::default();`
`13`	`13`	`\| ^^^^ access to union field`
`14`	`14`	`\|`
`15`	`15`	`= note: the field may not be properly initialized: using uninitialized data will cause undefined behavior`
`16`	`16`
`17`	`17`	`error[E0133]: access to union field is unsafe and requires unsafe function or block`
`18`		`- --> $DIR/union-unsafe.rs:52:6`
	`18`	`+ --> $DIR/union-unsafe.rs:53:6`
`19`	`19`	`\|`
`20`	`20`	`LL \| *u3.a = T::default();`
`21`	`21`	`\| ^^^^ access to union field`
`22`	`22`	`\|`
`23`	`23`	`= note: the field may not be properly initialized: using uninitialized data will cause undefined behavior`
`24`	`24`
`25`	`25`	`error[E0133]: access to union field is unsafe and requires unsafe function or block`
`26`		`- --> $DIR/union-unsafe.rs:60:13`
	`26`	`+ --> $DIR/union-unsafe.rs:61:13`
`27`	`27`	`\|`
`28`	`28`	`LL \| let a = u1.a;`
`29`	`29`	`\| ^^^^ access to union field`
`30`	`30`	`\|`
`31`	`31`	`= note: the field may not be properly initialized: using uninitialized data will cause undefined behavior`
`32`	`32`
`33`	`33`	`error[E0133]: access to union field is unsafe and requires unsafe function or block`
`34`		`- --> $DIR/union-unsafe.rs:63:14`
	`34`	`+ --> $DIR/union-unsafe.rs:64:14`
`35`	`35`	`\|`
`36`	`36`	`LL \| let U1 { a } = u1;`
`37`	`37`	`\| ^ access to union field`
`38`	`38`	`\|`
`39`	`39`	`= note: the field may not be properly initialized: using uninitialized data will cause undefined behavior`
`40`	`40`
`41`	`41`	`error[E0133]: access to union field is unsafe and requires unsafe function or block`
`42`		`- --> $DIR/union-unsafe.rs:64:12`
	`42`	`+ --> $DIR/union-unsafe.rs:65:12`
`43`	`43`	`\|`
`44`	`44`	`LL \| if let U1 { a: 12 } = u1 {}`
`45`	`45`	`\| ^^^^^^^^^^^^ access to union field`
`46`	`46`	`\|`
`47`	`47`	`= note: the field may not be properly initialized: using uninitialized data will cause undefined behavior`
`48`	`48`
`49`	`49`	`error[E0133]: access to union field is unsafe and requires unsafe function or block`
`50`		`- --> $DIR/union-unsafe.rs:69:6`
	`50`	`+ --> $DIR/union-unsafe.rs:66:12`
	`51`	`+ \|`
	`52`	`+LL \| if let Some(U1 { a: 13 }) = Some(u1) {}`
	`53`	`+ \| ^^^^^^^^^^^^^^^^^^ access to union field`
	`54`	`+ \|`
	`55`	`+ = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior`
	`56`	`+`
	`57`	`+error[E0133]: access to union field is unsafe and requires unsafe function or block`
	`58`	`+ --> $DIR/union-unsafe.rs:71:6`
`51`	`59`	`\|`
`52`	`60`	`LL \| *u2.a = String::from("new");`
`53`	`61`	`\| ^^^^ access to union field`
`54`	`62`	`\|`
`55`	`63`	`= note: the field may not be properly initialized: using uninitialized data will cause undefined behavior`
`56`	`64`
`57`	`65`	`error[E0133]: access to union field is unsafe and requires unsafe function or block`
`58`		`- --> $DIR/union-unsafe.rs:73:6`
	`66`	`+ --> $DIR/union-unsafe.rs:75:6`
`59`	`67`	`\|`
`60`	`68`	`LL \| *u3.a = 1;`
`61`	`69`	`\| ^^^^ access to union field`
`62`	`70`	`\|`
`63`	`71`	`= note: the field may not be properly initialized: using uninitialized data will cause undefined behavior`
`64`	`72`
`65`	`73`	`error[E0133]: access to union field is unsafe and requires unsafe function or block`
`66`		`- --> $DIR/union-unsafe.rs:77:6`
	`74`	`+ --> $DIR/union-unsafe.rs:79:6`
`67`	`75`	`\|`
`68`	`76`	`LL \| *u3.a = String::from("new");`
`69`	`77`	`\| ^^^^ access to union field`
`70`	`78`	`\|`
`71`	`79`	`= note: the field may not be properly initialized: using uninitialized data will cause undefined behavior`
`72`	`80`
`73`		`-error: aborting due to 9 previous errors`
	`81`	`+error: aborting due to 10 previous errors`
`74`	`82`
`75`	`83`	For more information about this error, try `rustc --explain E0133`.
Original file line number	Diff line number	Diff line change
`@@ -1,75 +1,83 @@`
`1`	`1`	`error[E0133]: access to union field is unsafe and requires unsafe function or block`
`2`		`- --> $DIR/union-unsafe.rs:33:6`
	`2`	`+ --> $DIR/union-unsafe.rs:34:6`
`3`	`3`	`\|`
`4`	`4`	`LL \| *(u.p) = 13;`
`5`	`5`	`\| ^^^^^ access to union field`
`6`	`6`	`\|`
`7`	`7`	`= note: the field may not be properly initialized: using uninitialized data will cause undefined behavior`
`8`	`8`
`9`	`9`	`error[E0133]: access to union field is unsafe and requires unsafe function or block`
`10`		`- --> $DIR/union-unsafe.rs:46:6`
	`10`	`+ --> $DIR/union-unsafe.rs:47:6`
`11`	`11`	`\|`
`12`	`12`	`LL \| *u3.a = T::default();`
`13`	`13`	`\| ^^^^ access to union field`
`14`	`14`	`\|`
`15`	`15`	`= note: the field may not be properly initialized: using uninitialized data will cause undefined behavior`
`16`	`16`
`17`	`17`	`error[E0133]: access to union field is unsafe and requires unsafe function or block`
`18`		`- --> $DIR/union-unsafe.rs:52:6`
	`18`	`+ --> $DIR/union-unsafe.rs:53:6`
`19`	`19`	`\|`
`20`	`20`	`LL \| *u3.a = T::default();`
`21`	`21`	`\| ^^^^ access to union field`
`22`	`22`	`\|`
`23`	`23`	`= note: the field may not be properly initialized: using uninitialized data will cause undefined behavior`
`24`	`24`
`25`	`25`	`error[E0133]: access to union field is unsafe and requires unsafe function or block`
`26`		`- --> $DIR/union-unsafe.rs:60:13`
	`26`	`+ --> $DIR/union-unsafe.rs:61:13`
`27`	`27`	`\|`
`28`	`28`	`LL \| let a = u1.a;`
`29`	`29`	`\| ^^^^ access to union field`
`30`	`30`	`\|`
`31`	`31`	`= note: the field may not be properly initialized: using uninitialized data will cause undefined behavior`
`32`	`32`
`33`	`33`	`error[E0133]: access to union field is unsafe and requires unsafe function or block`
`34`		`- --> $DIR/union-unsafe.rs:63:14`
	`34`	`+ --> $DIR/union-unsafe.rs:64:14`
`35`	`35`	`\|`
`36`	`36`	`LL \| let U1 { a } = u1;`
`37`	`37`	`\| ^ access to union field`
`38`	`38`	`\|`
`39`	`39`	`= note: the field may not be properly initialized: using uninitialized data will cause undefined behavior`
`40`	`40`
`41`	`41`	`error[E0133]: access to union field is unsafe and requires unsafe function or block`
`42`		`- --> $DIR/union-unsafe.rs:64:8`
	`42`	`+ --> $DIR/union-unsafe.rs:65:20`
`43`	`43`	`\|`
`44`	`44`	`LL \| if let U1 { a: 12 } = u1 {}`
`45`		`- \| ^^^^^^^^^^^^^^^^^^^^^ access to union field`
	`45`	`+ \| ^^ access to union field`
`46`	`46`	`\|`
`47`	`47`	`= note: the field may not be properly initialized: using uninitialized data will cause undefined behavior`
`48`	`48`
`49`	`49`	`error[E0133]: access to union field is unsafe and requires unsafe function or block`
`50`		`- --> $DIR/union-unsafe.rs:69:6`
	`50`	`+ --> $DIR/union-unsafe.rs:66:25`
	`51`	`+ \|`
	`52`	`+LL \| if let Some(U1 { a: 13 }) = Some(u1) {}`
	`53`	`+ \| ^^ access to union field`
	`54`	`+ \|`
	`55`	`+ = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior`
	`56`	`+`
	`57`	`+error[E0133]: access to union field is unsafe and requires unsafe function or block`
	`58`	`+ --> $DIR/union-unsafe.rs:71:6`
`51`	`59`	`\|`
`52`	`60`	`LL \| *u2.a = String::from("new");`
`53`	`61`	`\| ^^^^ access to union field`
`54`	`62`	`\|`
`55`	`63`	`= note: the field may not be properly initialized: using uninitialized data will cause undefined behavior`
`56`	`64`
`57`	`65`	`error[E0133]: access to union field is unsafe and requires unsafe function or block`
`58`		`- --> $DIR/union-unsafe.rs:73:6`
	`66`	`+ --> $DIR/union-unsafe.rs:75:6`
`59`	`67`	`\|`
`60`	`68`	`LL \| *u3.a = 1;`
`61`	`69`	`\| ^^^^ access to union field`
`62`	`70`	`\|`
`63`	`71`	`= note: the field may not be properly initialized: using uninitialized data will cause undefined behavior`
`64`	`72`
`65`	`73`	`error[E0133]: access to union field is unsafe and requires unsafe function or block`
`66`		`- --> $DIR/union-unsafe.rs:77:6`
	`74`	`+ --> $DIR/union-unsafe.rs:79:6`
`67`	`75`	`\|`
`68`	`76`	`LL \| *u3.a = String::from("new");`
`69`	`77`	`\| ^^^^ access to union field`
`70`	`78`	`\|`
`71`	`79`	`= note: the field may not be properly initialized: using uninitialized data will cause undefined behavior`
`72`	`80`
`73`		`-error: aborting due to 9 previous errors`
	`81`	`+error: aborting due to 10 previous errors`
`74`	`82`
`75`	`83`	For more information about this error, try `rustc --explain E0133`.
Original file line number	Diff line number	Diff line change
`@@ -9,4 +9,5 @@ pub(crate) struct NonZero<T>(pub(crate) T);`
`9`	`9`	`fn main() {`
`10`	`10`	`let mut x = unsafe { NonZero(1) };`
`11`	`11`	`let y = &mut x.0; //~ ERROR mutation of layout constrained field is unsafe`
	`12`	`+ if let Some(NonZero(ref mut y)) = Some(x) {} //~ ERROR mutation of layout constrained field is unsafe`
`12`	`13`	`}`