Improve dead code analysis

compiler/rustc_passes/src/dead.rs

@@ -277,7 +277,10 @@ impl<'tcx> MarkSymbolVisitor<'tcx> {
  pats: &[hir::PatField<'_>],
  ) {
  let variant = match self.typeck_results().node_type(lhs.hir_id).kind() {
- ty::Adt(adt, _) => adt.variant_of_res(res),
+ ty::Adt(adt, _) => {
+ self.check_def_id(adt.did());
+ adt.variant_of_res(res)
+ }
  _ => span_bug!(lhs.span, "non-ADT in struct pattern"),
  };
  for pat in pats {
@@ -297,7 +300,10 @@ impl<'tcx> MarkSymbolVisitor<'tcx> {
  dotdot: hir::DotDotPos,
  ) {
  let variant = match self.typeck_results().node_type(lhs.hir_id).kind() {
- ty::Adt(adt, _) => adt.variant_of_res(res),
+ ty::Adt(adt, _) => {
+ self.check_def_id(adt.did());
+ adt.variant_of_res(res)
+ }
  _ => {
  self.tcx.dcx().span_delayed_bug(lhs.span, "non-ADT in tuple struct pattern");
  return;
@@ -402,31 +408,6 @@ impl<'tcx> MarkSymbolVisitor<'tcx> {
  return false;
  }
 
- // don't ignore impls for Enums and pub Structs whose methods don't have self receiver,
- // cause external crate may call such methods to construct values of these types
- if let Some(local_impl_of) = impl_of.as_local()
- && let Some(local_def_id) = def_id.as_local()
- && let Some(fn_sig) =
- self.tcx.hir().fn_sig_by_hir_id(self.tcx.local_def_id_to_hir_id(local_def_id))
- && matches!(fn_sig.decl.implicit_self, hir::ImplicitSelfKind::None)
- && let TyKind::Path(hir::QPath::Resolved(_, path)) =
- self.tcx.hir().expect_item(local_impl_of).expect_impl().self_ty.kind
- && let Res::Def(def_kind, did) = path.res
- {
- match def_kind {
- // for example, #[derive(Default)] pub struct T(i32);
- // external crate can call T::default() to construct T,
- // so that don't ignore impl Default for pub Enum and Structs
- DefKind::Struct | DefKind::Union if self.tcx.visibility(did).is_public() => {
- return false;
- }
- // don't ignore impl Default for Enums,
- // cause we don't know which variant is constructed
- DefKind::Enum => return false,
- _ => (),
- };
- }
-
  if let Some(trait_of) = self.tcx.trait_id_of_impl(impl_of)
  && self.tcx.has_attr(trait_of, sym::rustc_trivial_field_reads)
  {
@@ -690,6 +671,9 @@ impl<'tcx> Visitor<'tcx> for MarkSymbolVisitor<'tcx> {
  self.handle_field_pattern_match(pat, res, fields);
  }
  PatKind::Path(ref qpath) => {
+ if let ty::Adt(adt, _) = self.typeck_results().node_type(pat.hir_id).kind() {
+ self.check_def_id(adt.did());
+ }
  let res = self.typeck_results().qpath_res(qpath, pat.hir_id);
  self.handle_res(res);
  }
@@ -845,7 +829,7 @@ fn check_item<'tcx>(
  // mark the method live if the self_ty is public,
  // or the method is public and may construct self
  if tcx.visibility(local_def_id).is_public()
- && (ty_and_all_fields_are_public || may_construct_self)
+ && (ty_and_all_fields_are_public || (ty_is_public && may_construct_self))
  {
  // if the impl item is public,
  // and the ty may be constructed or can be constructed in foreign crates,

library/core/src/default.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.
  ///

src/tools/rust-analyzer/crates/salsa/salsa-macros/src/database_storage.rs

@@ -241,11 +241,3 @@ impl Parse for QueryGroup {
  Ok(QueryGroup { group_path })
  }
 }
-
-struct Nothing;
-
-impl Parse for Nothing {
- fn parse(_input: ParseStream<'_>) -> syn::Result<Self> {
- Ok(Nothing)
- }
-}

tests/ui-fulldeps/deriving-global.rs

@@ -17,18 +17,21 @@ mod submod {
  // if any of these are implemented without global calls for any
  // function calls, then being in a submodule will (correctly)
  // cause errors about unrecognised module `std` (or `extra`)
+ #[allow(dead_code)]
  #[derive(PartialEq, PartialOrd, Eq, Ord, Hash, Clone, Debug, Encodable, Decodable)]
  enum A {
  A1(usize),
  A2(isize),
  }
 
+ #[allow(dead_code)]
  #[derive(PartialEq, PartialOrd, Eq, Ord, Hash, Clone, Debug, Encodable, Decodable)]
  struct B {
  x: usize,
  y: isize,
  }
 
+ #[allow(dead_code)]
  #[derive(PartialEq, PartialOrd, Eq, Ord, Hash, Clone, Debug, Encodable, Decodable)]
  struct C(usize, isize);
 }

tests/ui-fulldeps/deriving-hygiene.rs

@@ -20,6 +20,7 @@ pub const s: u8 = 1;
 pub const state: u8 = 1;
 pub const cmp: u8 = 1;
 
+#[allow(dead_code)]
 #[derive(Ord, Eq, PartialOrd, PartialEq, Debug, Decodable, Encodable, Hash)]
 struct Foo {}
 

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

@@ -7,6 +7,7 @@ pub trait Foo {
  fn foo() where [(); 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

@@ -2,6 +2,7 @@
 #![feature(adt_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/impl-trait/extra-impl-in-trait-impl.fixed

@@ -1,6 +1,8 @@
 //@ 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

@@ -1,6 +1,8 @@
 //@ 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:6:18
+ --> $DIR/extra-impl-in-trait-impl.rs:8:18
  |
 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:6:18
+ --> $DIR/extra-impl-in-trait-impl.rs:8:18
  |
 LL | impl<T: Default> impl Default for S<T> {
  | ^^^^^^^^^^^^
 
 error: unexpected `impl` keyword
- --> $DIR/extra-impl-in-trait-impl.rs:12:6
+ --> $DIR/extra-impl-in-trait-impl.rs:14:6
  |
 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:12:6
+ --> $DIR/extra-impl-in-trait-impl.rs:14:6
  |
 LL | impl impl Default for S2 {
  | ^^^^^^^^^^^^

tests/ui/lint/dead-code/issue-59003.rs

@@ -4,8 +4,8 @@
 
 #![deny(dead_code)]
 
+#[allow(dead_code)]
 struct Foo {
- #[allow(dead_code)]
  inner: u32,
 }
 

tests/ui/lint/dead-code/not-lint-adt-appeared-in-pattern.rs

@@ -0,0 +1,44 @@
+#![deny(dead_code)]
+
+#[repr(u8)]
+#[derive(Copy, Clone, Debug)]
+pub enum RecordField {
+ Target = 1,
+ Level,
+ Module,
+ File,
+ Line,
+ NumArgs,
+}
+
+unsafe trait Pod {}
+
+#[repr(transparent)]
+struct RecordFieldWrapper(RecordField);
+
+unsafe impl Pod for RecordFieldWrapper {}
+
+fn try_read<T: Pod>(buf: &[u8]) -> T {
+ unsafe { std::ptr::read_unaligned(buf.as_ptr() as *const T) }
+}
+
+pub fn foo(buf: &[u8]) -> RecordField {
+ let RecordFieldWrapper(tag) = try_read(buf);
+ tag
+}
+
+struct Foo(u8); //~ ERROR struct `Foo` is never constructed
+
+pub trait MyDefault {
+ fn default() -> Self;
+}
+
+impl MyDefault for Foo {
+ fn default() -> Foo {
+ let f = Foo(0);
+ let Foo(tag) = f;
+ Foo(tag)
+ }
+}
+
+fn main() {}

tests/ui/lint/dead-code/not-lint-adt-appeared-in-pattern.stderr

@@ -0,0 +1,14 @@
+error: struct `Foo` is never constructed
+ --> $DIR/not-lint-adt-appeared-in-pattern.rs:30:8
+ |
+LL | struct Foo(u8);
+ | ^^^
+ |
+note: the lint level is defined here
+ --> $DIR/not-lint-adt-appeared-in-pattern.rs:1:9
+ |
+LL | #![deny(dead_code)]
+ | ^^^^^^^^^
+
+error: aborting due to 1 previous error
+

tests/ui/lint/dead-code/unused-adt-impl-pub-trait-with-assoc-const.rs

@@ -1,8 +1,9 @@
 #![deny(dead_code)]
 
 struct T1; //~ ERROR struct `T1` is never constructed
-pub struct T2(i32); //~ ERROR struct `T2` is never constructed
-struct T3;
+struct T2; //~ ERROR struct `T2` is never constructed
+pub struct T3(i32); //~ ERROR struct `T3` is never constructed
+pub struct T4(i32); //~ ERROR field `0` is never read
 
 trait Trait1 { //~ ERROR trait `Trait1` is never used
  const UNUSED: i32;
@@ -11,13 +12,13 @@ trait Trait1 { //~ ERROR trait `Trait1` is never used
 }
 
 pub trait Trait2 {
- const USED: i32;
- fn used(&self) {}
+ const MAY_USED: i32;
+ fn may_used(&self) {}
 }
 
 pub trait Trait3 {
- const USED: i32;
- fn construct_self() -> Self;
+ const MAY_USED: i32;
+ fn may_used() -> Self;
 }
 
 impl Trait1 for T1 {
@@ -30,23 +31,34 @@ impl Trait1 for T1 {
 impl Trait1 for T2 {
  const UNUSED: i32 = 0;
  fn construct_self() -> Self {
- T2(0)
+ Self
  }
 }
 
 impl Trait2 for T1 {
- const USED: i32 = 0;
+ const MAY_USED: i32 = 0;
 }
 
 impl Trait2 for T2 {
- const USED: i32 = 0;
+ const MAY_USED: i32 = 0;
 }
 
-impl Trait3 for T3 {
- const USED: i32 = 0;
- fn construct_self() -> Self {
+impl Trait2 for T3 {
+ const MAY_USED: i32 = 0;
+}
+
+impl Trait3 for T2 {
+ const MAY_USED: i32 = 0;
+ fn may_used() -> Self {
  Self
  }
 }
 
+impl Trait3 for T4 {
+ const MAY_USED: i32 = 0;
+ fn may_used() -> Self {
+ T4(0)
+ }
+}
+
 fn main() {}

tests/ui/lint/dead-code/unused-adt-impl-pub-trait-with-assoc-const.stderr

@@ -11,16 +11,32 @@ LL | #![deny(dead_code)]
  | ^^^^^^^^^
 
 error: struct `T2` is never constructed
- --> $DIR/unused-adt-impl-pub-trait-with-assoc-const.rs:4:12
+ --> $DIR/unused-adt-impl-pub-trait-with-assoc-const.rs:4:8
  |
-LL | pub struct T2(i32);
+LL | struct T2;
+ | ^^
+
+error: struct `T3` is never constructed
+ --> $DIR/unused-adt-impl-pub-trait-with-assoc-const.rs:5:12
+ |
+LL | pub struct T3(i32);
  | ^^
 
+error: field `0` is never read
+ --> $DIR/unused-adt-impl-pub-trait-with-assoc-const.rs:6:15
+ |
+LL | pub struct T4(i32);
+ | -- ^^^
+ | |
+ | field in this struct
+ |
+ = help: consider removing this field
+
 error: trait `Trait1` is never used
- --> $DIR/unused-adt-impl-pub-trait-with-assoc-const.rs:7:7
+ --> $DIR/unused-adt-impl-pub-trait-with-assoc-const.rs:8:7
  |
 LL | trait Trait1 {
  | ^^^^^^
 
-error: aborting due to 3 previous errors
+error: aborting due to 5 previous errors
 

tests/ui/lint/dead-code/unused-struct-derive-default.rs

@@ -22,4 +22,5 @@ pub struct T2 {
 
 fn main() {
  let _x: Used = Default::default();
+ let _e: E = Default::default();
 }

tests/ui/lint/dead-code/unused-struct-derive-default.stderr

@@ -4,7 +4,6 @@ error: struct `T` is never constructed
 LL | struct T;
  | ^
  |
- = note: `T` has a derived impl for the trait `Default`, but this is intentionally ignored during dead code analysis
 note: the lint level is defined here
  --> $DIR/unused-struct-derive-default.rs:1:9
  |

tests/ui/parser/issues/issue-105366.fixed

@@ -1,5 +1,6 @@
 //@ run-rustfix
 
+#[allow(dead_code)]
 struct Foo;
 
 impl From<i32> for Foo {

tests/ui/parser/issues/issue-105366.rs

@@ -1,5 +1,6 @@
 //@ run-rustfix
 
+#[allow(dead_code)]
 struct Foo;
 
 fn From<i32> for Foo {

tests/ui/parser/issues/issue-105366.stderr

@@ -1,5 +1,5 @@
 error: you might have meant to write `impl` instead of `fn`
- --> $DIR/issue-105366.rs:5:1
+ --> $DIR/issue-105366.rs:6:1
  |
 LL | fn From<i32> for Foo {
  | ^^