Revert recent changes to dead code analysis

library/core/src/default.rs

@@ -103,6 +103,7 @@ use crate::ascii::Char as AsciiChar;
 /// ```
 #[cfg_attr(not(test), rustc_diagnostic_item = "Default")]
 #[stable(feature = "rust1", since = "1.0.0")]
+#[cfg_attr(not(bootstrap), rustc_trivial_field_reads)]
 pub trait Default: Sized {
     /// Returns the "default value" for a type.
     ///

library/std/src/sys/pal/unix/pipe.rs

@@ -47,6 +47,8 @@ pub fn anon_pipe() -> io::Result<(AnonPipe, AnonPipe)> {
 }
 
 impl AnonPipe {
+    #[allow(dead_code)]
+    // FIXME: This function seems legitimately unused.
     pub fn try_clone(&self) -> io::Result<Self> {
         self.0.duplicate().map(Self)
     }
@@ -85,6 +87,8 @@ impl AnonPipe {
         self.0.is_write_vectored()
     }
 
+    #[allow(dead_code)]
+    // FIXME: This function seems legitimately unused.
     pub fn as_file_desc(&self) -> &FileDesc {
         &self.0
     }

src/bootstrap/src/core/build_steps/check.rs

@@ -31,10 +31,6 @@ pub struct Std {
 }
 
 impl Std {
-    pub fn new(target: TargetSelection) -> Self {
-        Self::new_with_build_kind(target, None)
-    }
-
     pub fn new_with_build_kind(target: TargetSelection, kind: Option<Kind>) -> Self {
         Self { target, crates: vec![], override_build_kind: kind }
     }

tests/codegen-units/item-collection/generic-impl.rs

@@ -22,16 +22,16 @@ impl<T> Struct<T> {
     }
 }
 
-pub struct _LifeTimeOnly<'a> {
+pub struct LifeTimeOnly<'a> {
     _a: &'a u32,
 }
 
-impl<'a> _LifeTimeOnly<'a> {
-    //~ MONO_ITEM fn _LifeTimeOnly::<'_>::foo
+impl<'a> LifeTimeOnly<'a> {
+    //~ MONO_ITEM fn LifeTimeOnly::<'_>::foo
     pub fn foo(&self) {}
-    //~ MONO_ITEM fn _LifeTimeOnly::<'_>::bar
+    //~ MONO_ITEM fn LifeTimeOnly::<'_>::bar
     pub fn bar(&'a self) {}
-    //~ MONO_ITEM fn _LifeTimeOnly::<'_>::baz
+    //~ MONO_ITEM fn LifeTimeOnly::<'_>::baz
     pub fn baz<'b>(&'b self) {}
 
     pub fn non_instantiated<T>(&self) {}

tests/codegen-units/item-collection/overloaded-operators.rs

@@ -5,44 +5,44 @@
 
 use std::ops::{Add, Deref, Index, IndexMut};
 
-pub struct _Indexable {
+pub struct Indexable {
     data: [u8; 3],
 }
 
-impl Index<usize> for _Indexable {
+impl Index<usize> for Indexable {
     type Output = u8;
 
-    //~ MONO_ITEM fn <_Indexable as std::ops::Index<usize>>::index
+    //~ MONO_ITEM fn <Indexable as std::ops::Index<usize>>::index
     fn index(&self, index: usize) -> &Self::Output {
         if index >= 3 { &self.data[0] } else { &self.data[index] }
     }
 }
 
-impl IndexMut<usize> for _Indexable {
-    //~ MONO_ITEM fn <_Indexable as std::ops::IndexMut<usize>>::index_mut
+impl IndexMut<usize> for Indexable {
+    //~ MONO_ITEM fn <Indexable as std::ops::IndexMut<usize>>::index_mut
     fn index_mut(&mut self, index: usize) -> &mut Self::Output {
         if index >= 3 { &mut self.data[0] } else { &mut self.data[index] }
     }
 }
 
-//~ MONO_ITEM fn <_Equatable as std::cmp::PartialEq>::eq
-//~ MONO_ITEM fn <_Equatable as std::cmp::PartialEq>::ne
+//~ MONO_ITEM fn <Equatable as std::cmp::PartialEq>::eq
+//~ MONO_ITEM fn <Equatable as std::cmp::PartialEq>::ne
 #[derive(PartialEq)]
-pub struct _Equatable(u32);
+pub struct Equatable(u32);
 
-impl Add<u32> for _Equatable {
+impl Add<u32> for Equatable {
     type Output = u32;
 
-    //~ MONO_ITEM fn <_Equatable as std::ops::Add<u32>>::add
+    //~ MONO_ITEM fn <Equatable as std::ops::Add<u32>>::add
     fn add(self, rhs: u32) -> u32 {
         self.0 + rhs
     }
 }
 
-impl Deref for _Equatable {
+impl Deref for Equatable {
     type Target = u32;
 
-    //~ MONO_ITEM fn <_Equatable as std::ops::Deref>::deref
+    //~ MONO_ITEM fn <Equatable as std::ops::Deref>::deref
     fn deref(&self) -> &Self::Target {
         &self.0
     }

tests/ui/coherence/re-rebalance-coherence.rs

@@ -4,7 +4,6 @@
 extern crate re_rebalance_coherence_lib as lib;
 use lib::*;
 
-#[allow(dead_code)]
 struct Oracle;
 impl Backend for Oracle {}
 impl<'a, T:'a, Tab> QueryFragment<Oracle> for BatchInsert<'a, T, Tab> {}

tests/ui/const-generics/cross_crate_complex.rs

@@ -11,7 +11,6 @@ async fn foo() {
     async_in_foo(async_out_foo::<4>().await).await;
 }
 
-#[allow(dead_code)]
 struct Faz<const N: usize>;
 
 impl<const N: usize> Foo<N> for Faz<N> {}

tests/ui/const-generics/defaults/repr-c-issue-82792.rs

@@ -2,7 +2,6 @@
 
 //@ run-pass
 
-#[allow(dead_code)]
 #[repr(C)]
 pub struct Loaf<T: Sized, const N: usize = 1> {
     head: [T; N],

tests/ui/const-generics/generic_const_exprs/associated-consts.rs

@@ -16,8 +16,7 @@ impl BlockCipher for BarCipher {
     const BLOCK_SIZE: usize = 32;
 }
 
-#[allow(dead_code)]
-pub struct Block<C>(C);
+pub struct Block<C>(#[allow(dead_code)] C);
 
 pub fn test<C: BlockCipher, const M: usize>()
 where

tests/ui/const-generics/issues/issue-86535-2.rs

@@ -9,7 +9,6 @@ pub trait Foo {
         [(); Self::ASSOC_C]:;
 }
 
-#[allow(dead_code)]
 struct Bar<const N: &'static ()>;
 impl<const N: &'static ()> Foo for Bar<N> {
     const ASSOC_C: usize = 3;

tests/ui/const-generics/issues/issue-86535.rs

@@ -2,7 +2,6 @@
 #![feature(adt_const_params, unsized_const_params, generic_const_exprs)]
 #![allow(incomplete_features, unused_variables)]
 
-#[allow(dead_code)]
 struct F<const S: &'static str>;
 impl<const S: &'static str> X for F<{ S }> {
     const W: usize = 3;

tests/ui/const-generics/transparent-maybeunit-array-wrapper.rs

@@ -6,7 +6,6 @@
 
 use std::mem::MaybeUninit;
 
-#[allow(dead_code)]
 #[repr(transparent)]
 pub struct MaybeUninitWrapper<const N: usize>(MaybeUninit<[u64; N]>);
 

tests/ui/generic-associated-types/missing-bounds.fixed

@@ -2,7 +2,6 @@
 
 use std::ops::Add;
 
-#[allow(dead_code)]
 struct A<B>(B);
 
 impl<B> Add for A<B> where B: Add<Output = B> {
@@ -13,7 +12,6 @@ impl<B> Add for A<B> where B: Add<Output = B> {
     }
 }
 
-#[allow(dead_code)]
 struct C<B>(B);
 
 impl<B: Add<Output = B>> Add for C<B> {
@@ -24,7 +22,6 @@ impl<B: Add<Output = B>> Add for C<B> {
     }
 }
 
-#[allow(dead_code)]
 struct D<B>(B);
 
 impl<B: std::ops::Add<Output = B>> Add for D<B> {
@@ -35,7 +32,6 @@ impl<B: std::ops::Add<Output = B>> Add for D<B> {
     }
 }
 
-#[allow(dead_code)]
 struct E<B>(B);
 
 impl<B: Add<Output = B>> Add for E<B> where B: Add<Output = B> {

tests/ui/generic-associated-types/missing-bounds.rs

@@ -2,7 +2,6 @@
 
 use std::ops::Add;
 
-#[allow(dead_code)]
 struct A<B>(B);
 
 impl<B> Add for A<B> where B: Add {
@@ -13,7 +12,6 @@ impl<B> Add for A<B> where B: Add {
     }
 }
 
-#[allow(dead_code)]
 struct C<B>(B);
 
 impl<B: Add> Add for C<B> {
@@ -24,7 +22,6 @@ impl<B: Add> Add for C<B> {
     }
 }
 
-#[allow(dead_code)]
 struct D<B>(B);
 
 impl<B> Add for D<B> {
@@ -35,7 +32,6 @@ impl<B> Add for D<B> {
     }
 }
 
-#[allow(dead_code)]
 struct E<B>(B);
 
 impl<B: Add> Add for E<B> where <B as Add>::Output = B {

tests/ui/generic-associated-types/missing-bounds.stderr

@@ -1,5 +1,5 @@
 error: equality constraints are not yet supported in `where` clauses
-  --> $DIR/missing-bounds.rs:41:33
+  --> $DIR/missing-bounds.rs:37:33
    |
 LL | impl<B: Add> Add for E<B> where <B as Add>::Output = B {
    |                                 ^^^^^^^^^^^^^^^^^^^^^^ not supported
@@ -11,7 +11,7 @@ LL | impl<B: Add> Add for E<B> where B: Add<Output = B> {
    |                                 ~~~~~~~~~~~~~~~~~~
 
 error[E0308]: mismatched types
-  --> $DIR/missing-bounds.rs:12:11
+  --> $DIR/missing-bounds.rs:11:11
    |
 LL | impl<B> Add for A<B> where B: Add {
    |      - expected this type parameter
@@ -24,14 +24,14 @@ LL |         A(self.0 + rhs.0)
    = note: expected type parameter `B`
              found associated type `<B as Add>::Output`
 help: the type constructed contains `<B as Add>::Output` due to the type of the argument passed
-  --> $DIR/missing-bounds.rs:12:9
+  --> $DIR/missing-bounds.rs:11:9
    |
 LL |         A(self.0 + rhs.0)
    |         ^^--------------^
    |           |
    |           this argument influences the type of `A`
 note: tuple struct defined here
-  --> $DIR/missing-bounds.rs:6:8
+  --> $DIR/missing-bounds.rs:5:8
    |
 LL | struct A<B>(B);
    |        ^
@@ -41,7 +41,7 @@ LL | impl<B> Add for A<B> where B: Add<Output = B> {
    |                                  ++++++++++++
 
 error[E0308]: mismatched types
-  --> $DIR/missing-bounds.rs:23:14
+  --> $DIR/missing-bounds.rs:21:14
    |
 LL | impl<B: Add> Add for C<B> {
    |      - expected this type parameter
@@ -54,7 +54,7 @@ LL |         Self(self.0 + rhs.0)
    = note: expected type parameter `B`
              found associated type `<B as Add>::Output`
 note: tuple struct defined here
-  --> $DIR/missing-bounds.rs:17:8
+  --> $DIR/missing-bounds.rs:15:8
    |
 LL | struct C<B>(B);
    |        ^
@@ -64,7 +64,7 @@ LL | impl<B: Add<Output = B>> Add for C<B> {
    |            ++++++++++++
 
 error[E0369]: cannot add `B` to `B`
-  --> $DIR/missing-bounds.rs:34:21
+  --> $DIR/missing-bounds.rs:31:21
    |
 LL |         Self(self.0 + rhs.0)
    |              ------ ^ ----- B
@@ -77,7 +77,7 @@ LL | impl<B: std::ops::Add<Output = B>> Add for D<B> {
    |       +++++++++++++++++++++++++++
 
 error[E0308]: mismatched types
-  --> $DIR/missing-bounds.rs:46:14
+  --> $DIR/missing-bounds.rs:42:14
    |
 LL | impl<B: Add> Add for E<B> where <B as Add>::Output = B {
    |      - expected this type parameter
@@ -90,7 +90,7 @@ LL |         Self(self.0 + rhs.0)
    = note: expected type parameter `B`
              found associated type `<B as Add>::Output`
 note: tuple struct defined here
-  --> $DIR/missing-bounds.rs:39:8
+  --> $DIR/missing-bounds.rs:35:8
    |
 LL | struct E<B>(B);
    |        ^

tests/ui/impl-trait/extra-impl-in-trait-impl.fixed

@@ -1,8 +1,6 @@
 //@ run-rustfix
 
-#[allow(dead_code)]
 struct S<T>(T);
-#[allow(dead_code)]
 struct S2;
 
 impl<T: Default> Default for S<T> {

tests/ui/impl-trait/extra-impl-in-trait-impl.rs

@@ -1,8 +1,6 @@
 //@ run-rustfix
 
-#[allow(dead_code)]
 struct S<T>(T);
-#[allow(dead_code)]
 struct S2;
 
 impl<T: Default> impl Default for S<T> {

tests/ui/impl-trait/extra-impl-in-trait-impl.stderr

@@ -1,23 +1,23 @@
 error: unexpected `impl` keyword
-  --> $DIR/extra-impl-in-trait-impl.rs:8:18
+  --> $DIR/extra-impl-in-trait-impl.rs:6:18
    |
 LL | impl<T: Default> impl Default for S<T> {
    |                  ^^^^^ help: remove the extra `impl`
    |
 note: this is parsed as an `impl Trait` type, but a trait is expected at this position
-  --> $DIR/extra-impl-in-trait-impl.rs:8:18
+  --> $DIR/extra-impl-in-trait-impl.rs:6:18
    |
 LL | impl<T: Default> impl Default for S<T> {
    |                  ^^^^^^^^^^^^
 
 error: unexpected `impl` keyword
-  --> $DIR/extra-impl-in-trait-impl.rs:14:6
+  --> $DIR/extra-impl-in-trait-impl.rs:12:6
    |
 LL | impl impl Default for S2 {
    |      ^^^^^ help: remove the extra `impl`
    |
 note: this is parsed as an `impl Trait` type, but a trait is expected at this position
-  --> $DIR/extra-impl-in-trait-impl.rs:14:6
+  --> $DIR/extra-impl-in-trait-impl.rs:12:6
    |
 LL | impl impl Default for S2 {
    |      ^^^^^^^^^^^^

tests/ui/issues/issue-5708.rs

@@ -44,7 +44,6 @@ pub trait MyTrait<T> {
     fn dummy(&self, t: T) -> T { panic!() }
 }
 
-#[allow(dead_code)]
 pub struct MyContainer<'a, T:'a> {
     foos: Vec<&'a (dyn MyTrait<T>+'a)> ,
 }