Visit patterns in THIR let expressions

This fixes some THIR unsafety checking errors not being emitted for
let expressions in these situations.

8 files changed, 66 insertions, 38 deletions

diff --git a/compiler/rustc_middle/src/thir/visit.rs b/compiler/rustc_middle/src/thir/visit.rs
index d03d92c3a4b..8feefb4c03c 100644
--- 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
index 373ed61ff87..3d895c131a8 100644
--- 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
index 544213dbc55..15f059ffa48 100644
--- a/tests/ui/union/union-unsafe.mir.stderr
+++ b/tests/ui/union/union-unsafe.mir.stderr
@@ -1,5 +1,5 @@
 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
@@ -7,7 +7,7 @@ LL |     *(u.p) = 13;
    = 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
@@ -15,7 +15,7 @@ LL |     *u3.a = T::default();
    = 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
@@ -23,7 +23,7 @@ LL |     *u3.a = T::default();
    = 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
@@ -31,7 +31,7 @@ LL |     let a = u1.a;
    = 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
@@ -39,7 +39,7 @@ LL |     let U1 { a } = u1;
    = 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
@@ -47,7 +47,15 @@ LL |     if let U1 { a: 12 } = u1 {}
    = 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
@@ -55,7 +63,7 @@ LL |     *u2.a = String::from("new");
    = 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
@@ -63,13 +71,13 @@ LL |     *u3.a = 1;
    = 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
index 5e1837a901d..d1465486f77 100644
--- 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
index f959fe5bdb5..9ce835497c5 100644
--- a/tests/ui/union/union-unsafe.thir.stderr
+++ b/tests/ui/union/union-unsafe.thir.stderr
@@ -1,5 +1,5 @@
 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
@@ -7,7 +7,7 @@ LL |     *(u.p) = 13;
    = 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
@@ -15,7 +15,7 @@ LL |     *u3.a = T::default();
    = 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
@@ -23,7 +23,7 @@ LL |     *u3.a = T::default();
    = 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
@@ -31,7 +31,7 @@ LL |     let a = u1.a;
    = 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
@@ -39,15 +39,23 @@ LL |     let U1 { a } = u1;
    = 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
@@ -55,7 +63,7 @@ LL |     *u2.a = String::from("new");
    = 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
@@ -63,13 +71,13 @@ LL |     *u3.a = 1;
    = 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
index 427843f8d45..dc6bd72f56c 100644
--- 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
index 9a6bb18f926..ad9d598aba2 100644
--- 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
index 427843f8d45..dc6bd72f56c 100644
--- 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`.