Improve dead code analysis for structs and traits defined locally

Author: mu001999

compiler/rustc_incremental/messages.ftl

@@ -99,6 +99,4 @@ incremental_unrecognized_depnode = unrecognized `DepNode` variant: {$name}
 
 incremental_unrecognized_depnode_label = dep-node label `{$label}` not recognized
 
-incremental_write_dep_graph = failed to write dependency graph to `{$path}`: {$err}
-
 incremental_write_new = failed to write {$name} to `{$path}`: {$err}

compiler/rustc_incremental/src/errors.rs

@@ -272,13 +272,6 @@ pub struct LoadDepGraph {
     pub err: std::io::Error,
 }
 
-#[derive(Diagnostic)]
-#[diag(incremental_write_dep_graph)]
-pub struct WriteDepGraph<'a> {
-    pub path: &'a Path,
-    pub err: std::io::Error,
-}
-
 #[derive(Diagnostic)]
 #[diag(incremental_move_dep_graph)]
 pub struct MoveDepGraph<'a> {

compiler/rustc_passes/messages.ftl

@@ -471,10 +471,6 @@ passes_must_not_suspend =
     `must_not_suspend` attribute should be applied to a struct, enum, or trait
     .label = is not a struct, enum, or trait
 
-passes_must_use_async =
-    `must_use` attribute on `async` functions applies to the anonymous `Future` returned by the function, not the value within
-    .label = this attribute does nothing, the `Future`s returned by async functions are already `must_use`
-
 passes_must_use_no_effect =
     `#[must_use]` has no effect when applied to {$article} {$target}
 

compiler/rustc_passes/src/dead.rs

@@ -371,13 +371,6 @@ pub struct FfiConstInvalidTarget {
     pub attr_span: Span,
 }
 
-#[derive(LintDiagnostic)]
-#[diag(passes_must_use_async)]
-pub struct MustUseAsync {
-    #[label]
-    pub span: Span,
-}
-
 #[derive(LintDiagnostic)]
 #[diag(passes_must_use_no_effect)]
 pub struct MustUseNoEffect {

compiler/rustc_passes/src/errors.rs

@@ -4,7 +4,6 @@ use crate::layout;
 pub(crate) trait QueryContext {
     type Def: layout::Def;
     type Ref: layout::Ref;
-    type Scope: Copy;
 }
 
 #[cfg(test)]
@@ -28,20 +27,17 @@ pub(crate) mod test {
     impl QueryContext for UltraMinimal {
         type Def = Def;
         type Ref = !;
-        type Scope = ();
     }
 }
 
 #[cfg(feature = "rustc")]
 mod rustc {
-    use rustc_middle::ty::{Ty, TyCtxt};
+    use rustc_middle::ty::TyCtxt;
 
     use super::*;
 
     impl<'tcx> super::QueryContext for TyCtxt<'tcx> {
         type Def = layout::rustc::Def<'tcx>;
         type Ref = layout::rustc::Ref<'tcx>;
-
-        type Scope = Ty<'tcx>;
     }
 }

compiler/rustc_transmute/src/maybe_transmutable/query_context.rs

@@ -1,4 +1,3 @@
-use core::alloc::{AllocError, Allocator, Layout};
 use core::cell::Cell;
 use core::mem::MaybeUninit;
 use core::ptr::NonNull;
@@ -58,124 +57,3 @@ fn box_deref_lval() {
     x.set(1000);
     assert_eq!(x.get(), 1000);
 }
-
-pub struct ConstAllocator;
-
-unsafe impl Allocator for ConstAllocator {
-    fn allocate(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
-        match layout.size() {
-            0 => Ok(NonNull::slice_from_raw_parts(layout.dangling(), 0)),
-            _ => unsafe {
-                let ptr = core::intrinsics::const_allocate(layout.size(), layout.align());
-                Ok(NonNull::new_unchecked(ptr as *mut [u8; 0] as *mut [u8]))
-            },
-        }
-    }
-
-    unsafe fn deallocate(&self, _ptr: NonNull<u8>, layout: Layout) {
-        match layout.size() {
-            0 => { /* do nothing */ }
-            _ => { /* do nothing too */ }
-        }
-    }
-
-    fn allocate_zeroed(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
-        let ptr = self.allocate(layout)?;
-        if layout.size() > 0 {
-            unsafe {
-                ptr.as_mut_ptr().write_bytes(0, layout.size());
-            }
-        }
-        Ok(ptr)
-    }
-
-    unsafe fn grow(
-        &self,
-        ptr: NonNull<u8>,
-        old_layout: Layout,
-        new_layout: Layout,
-    ) -> Result<NonNull<[u8]>, AllocError> {
-        debug_assert!(
-            new_layout.size() >= old_layout.size(),
-            "`new_layout.size()` must be greater than or equal to `old_layout.size()`"
-        );
-
-        let new_ptr = self.allocate(new_layout)?;
-        if new_layout.size() > 0 {
-            // Safety: `new_ptr` is valid for writes and `ptr` for reads of
-            // `old_layout.size()`, because `new_layout.size() >=
-            // old_layout.size()` (which is an invariant that must be upheld by
-            // callers).
-            unsafe {
-                new_ptr.as_mut_ptr().copy_from_nonoverlapping(ptr.as_ptr(), old_layout.size());
-            }
-            // Safety: `ptr` is never used again is also an invariant which must
-            // be upheld by callers.
-            unsafe {
-                self.deallocate(ptr, old_layout);
-            }
-        }
-        Ok(new_ptr)
-    }
-
-    unsafe fn grow_zeroed(
-        &self,
-        ptr: NonNull<u8>,
-        old_layout: Layout,
-        new_layout: Layout,
-    ) -> Result<NonNull<[u8]>, AllocError> {
-        // Safety: Invariants of `grow_zeroed` and `grow` are the same, and must
-        // be enforced by callers.
-        let new_ptr = unsafe { self.grow(ptr, old_layout, new_layout)? };
-        if new_layout.size() > 0 {
-            let old_size = old_layout.size();
-            let new_size = new_layout.size();
-            let raw_ptr = new_ptr.as_mut_ptr();
-            // Safety:
-            // - `grow` returned Ok, so the returned pointer must be valid for
-            //   `new_size` bytes
-            // - `new_size` must be larger than `old_size`, which is an
-            //   invariant which must be upheld by callers.
-            unsafe {
-                raw_ptr.add(old_size).write_bytes(0, new_size - old_size);
-            }
-        }
-        Ok(new_ptr)
-    }
-
-    unsafe fn shrink(
-        &self,
-        ptr: NonNull<u8>,
-        old_layout: Layout,
-        new_layout: Layout,
-    ) -> Result<NonNull<[u8]>, AllocError> {
-        debug_assert!(
-            new_layout.size() <= old_layout.size(),
-            "`new_layout.size()` must be smaller than or equal to `old_layout.size()`"
-        );
-
-        let new_ptr = self.allocate(new_layout)?;
-        if new_layout.size() > 0 {
-            // Safety: `new_ptr` and `ptr` are valid for reads/writes of
-            // `new_layout.size()` because of the invariants of shrink, which
-            // include `new_layout.size()` being smaller than (or equal to)
-            // `old_layout.size()`.
-            unsafe {
-                new_ptr.as_mut_ptr().copy_from_nonoverlapping(ptr.as_ptr(), new_layout.size());
-            }
-            // Safety: `ptr` is never used again is also an invariant which must
-            // be upheld by callers.
-            unsafe {
-                self.deallocate(ptr, old_layout);
-            }
-        }
-        Ok(new_ptr)
-    }
-
-    fn by_ref(&self) -> &Self
-    where
-        Self: Sized,
-    {
-        self
-    }
-}

library/alloc/tests/boxed.rs

@@ -103,7 +103,6 @@ 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/core/src/default.rs

@@ -4,7 +4,7 @@
 
 trait Tr1: Copy { type As1: Copy; }
 trait Tr2: Copy { type As2: Copy; }
-trait Tr3: Copy { type As3: Copy; }
+trait Tr3: Copy { #[allow(dead_code)] type As3: Copy; }
 trait Tr4<'a>: Copy { type As4: Copy; }
 trait Tr5: Copy { type As5: Copy; }
 

tests/ui/associated-type-bounds/union-bounds.rs

@@ -11,6 +11,7 @@ impl Fiz for bool {}
 
 trait Grault {
     type A;
+    #[allow(dead_code)]
     type B;
 }
 

tests/ui/associated-types/impl-wf-cycle-5.fixed

@@ -11,6 +11,7 @@ impl Fiz for bool {}
 
 trait Grault {
     type A;
+    #[allow(dead_code)]
     type B;
 }
 

tests/ui/associated-types/impl-wf-cycle-5.rs

@@ -1,5 +1,5 @@
 error[E0275]: overflow evaluating the requirement `<(T,) as Grault>::A == _`
-  --> $DIR/impl-wf-cycle-5.rs:22:1
+  --> $DIR/impl-wf-cycle-5.rs:23:1
    |
 LL | / impl<T> Grault for (T,)
 LL | |
@@ -12,7 +12,7 @@ LL |       type A = ();
    |       ------ associated type `<(T,) as Grault>::A` is specified here
    |
 note: required for `(T,)` to implement `Grault`
-  --> $DIR/impl-wf-cycle-5.rs:22:9
+  --> $DIR/impl-wf-cycle-5.rs:23:9
    |
 LL | impl<T> Grault for (T,)
    |         ^^^^^^     ^^^^

tests/ui/associated-types/impl-wf-cycle-5.stderr

@@ -11,6 +11,7 @@ impl Fiz for bool {}
 
 trait Grault {
     type A;
+    #[allow(dead_code)]
     type B;
 }
 

tests/ui/associated-types/impl-wf-cycle-6.fixed

@@ -11,6 +11,7 @@ impl Fiz for bool {}
 
 trait Grault {
     type A;
+    #[allow(dead_code)]
     type B;
 }
 

tests/ui/associated-types/impl-wf-cycle-6.rs

@@ -1,5 +1,5 @@
 error[E0275]: overflow evaluating the requirement `<(T,) as Grault>::A == _`
-  --> $DIR/impl-wf-cycle-6.rs:22:1
+  --> $DIR/impl-wf-cycle-6.rs:23:1
    |
 LL | / impl<T: Grault> Grault for (T,)
 LL | |
@@ -11,7 +11,7 @@ LL |       type A = ();
    |       ------ associated type `<(T,) as Grault>::A` is specified here
    |
 note: required for `(T,)` to implement `Grault`
-  --> $DIR/impl-wf-cycle-6.rs:22:17
+  --> $DIR/impl-wf-cycle-6.rs:23:17
    |
 LL | impl<T: Grault> Grault for (T,)
    |                 ^^^^^^     ^^^^

tests/ui/associated-types/impl-wf-cycle-6.stderr

@@ -11,7 +11,7 @@ async fn foo() {
     async_in_foo(async_out_foo::<4>().await).await;
 }
 
-struct Faz<const N: usize>;
+struct Faz<const N: usize>; //~ WARN struct `Faz` is never constructed
 
 impl<const N: usize> Foo<N> for Faz<N> {}
 impl<const N: usize> Bar<N> for Faz<N> {

tests/ui/const-generics/cross_crate_complex.rs

@@ -0,0 +1,10 @@
+warning: struct `Faz` is never constructed
+  --> $DIR/cross_crate_complex.rs:14:8
+   |
+LL | struct Faz<const N: usize>;
+   |        ^^^
+   |
+   = note: `#[warn(dead_code)]` on by default
+
+warning: 1 warning emitted
+

tests/ui/const-generics/cross_crate_complex.stderr

@@ -9,7 +9,7 @@ pub trait Foo {
         [(); Self::ASSOC_C]:;
 }
 
-struct Bar<const N: &'static ()>;
+struct Bar<const N: &'static ()>; //~ WARN struct `Bar` is never constructed
 impl<const N: &'static ()> Foo for Bar<N> {
     const ASSOC_C: usize = 3;
 

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

@@ -0,0 +1,10 @@
+warning: struct `Bar` is never constructed
+  --> $DIR/issue-86535-2.rs:12:8
+   |
+LL | struct Bar<const N: &'static ()>;
+   |        ^^^
+   |
+   = note: `#[warn(dead_code)]` on by default
+
+warning: 1 warning emitted
+

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

@@ -2,7 +2,7 @@
 #![feature(adt_const_params, unsized_const_params, generic_const_exprs)]
 #![allow(incomplete_features, unused_variables)]
 
-struct F<const S: &'static str>;
+struct F<const S: &'static str>; //~ WARN struct `F` is never constructed
 impl<const S: &'static str> X for F<{ S }> {
     const W: usize = 3;
 

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

@@ -0,0 +1,10 @@
+warning: struct `F` is never constructed
+  --> $DIR/issue-86535.rs:5:8
+   |
+LL | struct F<const S: &'static str>;
+   |        ^
+   |
+   = note: `#[warn(dead_code)]` on by default
+
+warning: 1 warning emitted
+

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

@@ -6,7 +6,7 @@ macro_rules! define_vec {
     () => (
         mod foo {
             #[derive(PartialEq)]
-            pub struct bar;
+            pub struct bar; //~ WARN struct `bar` is never constructed
         }
     )
 }

tests/ui/deriving/deriving-in-macro.rs

@@ -0,0 +1,14 @@
+warning: struct `bar` is never constructed
+  --> $DIR/deriving-in-macro.rs:9:24
+   |
+LL |             pub struct bar;
+   |                        ^^^
+...
+LL | define_vec![];
+   | ------------- in this macro invocation
+   |
+   = note: `#[warn(dead_code)]` on by default
+   = note: this warning originates in the macro `define_vec` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+warning: 1 warning emitted
+

tests/ui/deriving/deriving-in-macro.stderr

@@ -10,6 +10,7 @@ trait Collection<T> {
     type Iter<'iter>: Iterator<Item=&'iter T> where T: 'iter, Self: 'iter;
     type Family: CollectionFamily;
     // Test associated type defaults with parameters
+    #[allow(dead_code)]
     type Sibling<U>: Collection<U> =
         <<Self as Collection<T>>::Family as CollectionFamily>::Member<U>;
 

tests/ui/generic-associated-types/collections.rs

@@ -1,5 +1,7 @@
 //@ run-rustfix
 
+#![allow(dead_code)]
+
 use std::ops::Add;
 
 struct A<B>(B);

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

@@ -1,5 +1,7 @@
 //@ run-rustfix
 
+#![allow(dead_code)]
+
 use std::ops::Add;
 
 struct A<B>(B);