From 71e57ad0d9f89aade32ff32e605a2461f7212a69 Mon Sep 17 00:00:00 2001
From: "Felix S. Klock II" <pnkfelix@pnkfx.org>
Date: Mon, 15 Mar 2021 16:39:41 -0400
Subject: [PATCH] Revert PR 81473 to resolve (on beta) issues 81626 and 81658.

Revert "Add missing brace"

This reverts commit 85ad773049536d7fed9a94ae0ac74f97135c8655.

Revert "Simplify base_expr"

This reverts commit 899aae465eb4ef295dc1eeb2603f744568e0768c.

Revert "Warn write-only fields"

This reverts commit d3c69a4c0dd98af2611b7553d1a65afef6a6ccb0.
---
 compiler/rustc_passes/src/dead.rs             | 15 -----------
 .../borrowck/borrowck-assign-to-subfield.rs   |  1 -
 .../ui/lint/dead-code/write-only-field.rs     | 20 --------------
 .../ui/lint/dead-code/write-only-field.stderr | 26 -------------------
 4 files changed, 62 deletions(-)
 delete mode 100644 src/test/ui/lint/dead-code/write-only-field.rs
 delete mode 100644 src/test/ui/lint/dead-code/write-only-field.stderr

diff --git a/compiler/rustc_passes/src/dead.rs b/compiler/rustc_passes/src/dead.rs
index 0d096a0556ba1..3b1b53553d5e4 100644
--- a/compiler/rustc_passes/src/dead.rs
+++ b/compiler/rustc_passes/src/dead.rs
@@ -37,15 +37,6 @@ fn should_explore(tcx: TyCtxt<'_>, hir_id: hir::HirId) -> bool {
     )
 }
 
-fn base_expr<'a>(mut expr: &'a hir::Expr<'a>) -> &'a hir::Expr<'a> {
-    loop {
-        match expr.kind {
-            hir::ExprKind::Field(base, ..) => expr = base,
-            _ => return expr,
-        }
-    }
-}
-
 struct MarkSymbolVisitor<'tcx> {
     worklist: Vec<hir::HirId>,
     tcx: TyCtxt<'tcx>,
@@ -272,12 +263,6 @@ impl<'tcx> Visitor<'tcx> for MarkSymbolVisitor<'tcx> {
             hir::ExprKind::MethodCall(..) => {
                 self.lookup_and_handle_method(expr.hir_id);
             }
-            hir::ExprKind::Assign(ref left, ref right, ..) => {
-                // Ignore write to field
-                self.visit_expr(base_expr(left));
-                self.visit_expr(right);
-                return;
-            }
             hir::ExprKind::Field(ref lhs, ..) => {
                 self.handle_field_access(&lhs, expr.hir_id);
             }
diff --git a/src/test/ui/borrowck/borrowck-assign-to-subfield.rs b/src/test/ui/borrowck/borrowck-assign-to-subfield.rs
index dfa3a561ec7ee..050d702b625ab 100644
--- a/src/test/ui/borrowck/borrowck-assign-to-subfield.rs
+++ b/src/test/ui/borrowck/borrowck-assign-to-subfield.rs
@@ -1,6 +1,5 @@
 // run-pass
 // pretty-expanded FIXME #23616
-#![allow(dead_code)]
 
 pub fn main() {
     struct A {
diff --git a/src/test/ui/lint/dead-code/write-only-field.rs b/src/test/ui/lint/dead-code/write-only-field.rs
deleted file mode 100644
index 78cfcfda8f971..0000000000000
--- a/src/test/ui/lint/dead-code/write-only-field.rs
+++ /dev/null
@@ -1,20 +0,0 @@
-#![deny(dead_code)]
-
-struct S {
-    f: i32, //~ ERROR: field is never read
-    sub: Sub, //~ ERROR: field is never read
-}
-
-struct Sub {
-    f: i32, //~ ERROR: field is never read
-}
-
-fn field_write(s: &mut S) {
-    s.f = 1;
-    s.sub.f = 2;
-}
-
-fn main() {
-    let mut s = S { f: 0, sub: Sub { f: 0 } };
-    field_write(&mut s);
-}
diff --git a/src/test/ui/lint/dead-code/write-only-field.stderr b/src/test/ui/lint/dead-code/write-only-field.stderr
deleted file mode 100644
index 70d2149665b20..0000000000000
--- a/src/test/ui/lint/dead-code/write-only-field.stderr
+++ /dev/null
@@ -1,26 +0,0 @@
-error: field is never read: `f`
-  --> $DIR/write-only-field.rs:4:5
-   |
-LL |     f: i32,
-   |     ^^^^^^
-   |
-note: the lint level is defined here
-  --> $DIR/write-only-field.rs:1:9
-   |
-LL | #![deny(dead_code)]
-   |         ^^^^^^^^^
-
-error: field is never read: `sub`
-  --> $DIR/write-only-field.rs:5:5
-   |
-LL |     sub: Sub,
-   |     ^^^^^^^^
-
-error: field is never read: `f`
-  --> $DIR/write-only-field.rs:9:5
-   |
-LL |     f: i32,
-   |     ^^^^^^
-
-error: aborting due to 3 previous errors
-