Rollup merge of #126018 - nnethercote:rm-box_pointers-lint, r=lcnr

Remove the `box_pointers` lint.

As the comment says, this lint "is mostly historical, and not particularly useful". It's not worth keeping it around.

r? ``@estebank``

3 files changed, 7 insertions, 86 deletions

diff --git a/compiler/rustc_lint/src/builtin.rs b/compiler/rustc_lint/src/builtin.rs
index 98318cd14d9..79c8046f9b7 100644
--- a/compiler/rustc_lint/src/builtin.rs
+++ b/compiler/rustc_lint/src/builtin.rs
@@ -24,9 +24,9 @@ use crate::fluent_generated as fluent;
 use crate::{
     errors::BuiltinEllipsisInclusiveRangePatterns,
     lints::{
-        BuiltinAnonymousParams, BuiltinBoxPointers, BuiltinConstNoMangle,
-        BuiltinDeprecatedAttrLink, BuiltinDeprecatedAttrLinkSuggestion, BuiltinDeprecatedAttrUsed,
-        BuiltinDerefNullptr, BuiltinEllipsisInclusiveRangePatternsLint, BuiltinExplicitOutlives,
+        BuiltinAnonymousParams, BuiltinConstNoMangle, BuiltinDeprecatedAttrLink,
+        BuiltinDeprecatedAttrLinkSuggestion, BuiltinDeprecatedAttrUsed, BuiltinDerefNullptr,
+        BuiltinEllipsisInclusiveRangePatternsLint, BuiltinExplicitOutlives,
         BuiltinExplicitOutlivesSuggestion, BuiltinFeatureIssueNote, BuiltinIncompleteFeatures,
         BuiltinIncompleteFeaturesHelp, BuiltinInternalFeatures, BuiltinKeywordIdents,
         BuiltinMissingCopyImpl, BuiltinMissingDebugImpl, BuiltinMissingDoc,
@@ -56,7 +56,6 @@ use rustc_middle::bug;
 use rustc_middle::lint::in_external_macro;
 use rustc_middle::ty::layout::LayoutOf;
 use rustc_middle::ty::print::with_no_trimmed_paths;
-use rustc_middle::ty::GenericArgKind;
 use rustc_middle::ty::TypeVisitableExt;
 use rustc_middle::ty::Upcast;
 use rustc_middle::ty::{self, Ty, TyCtxt, VariantDef};
@@ -135,80 +134,6 @@ impl EarlyLintPass for WhileTrue {
 }
 
 declare_lint! {
-    /// The `box_pointers` lints use of the Box type.
-    ///
-    /// ### Example
-    ///
-    /// ```rust,compile_fail
-    /// #![deny(box_pointers)]
-    /// struct Foo {
-    ///     x: Box<i32>,
-    /// }
-    /// ```
-    ///
-    /// {{produces}}
-    ///
-    /// ### Explanation
-    ///
-    /// This lint is mostly historical, and not particularly useful. `Box<T>`
-    /// used to be built into the language, and the only way to do heap
-    /// allocation. Today's Rust can call into other allocators, etc.
-    BOX_POINTERS,
-    Allow,
-    "use of owned (Box type) heap memory"
-}
-
-declare_lint_pass!(BoxPointers => [BOX_POINTERS]);
-
-impl BoxPointers {
-    fn check_heap_type(&self, cx: &LateContext<'_>, span: Span, ty: Ty<'_>) {
-        for leaf in ty.walk() {
-            if let GenericArgKind::Type(leaf_ty) = leaf.unpack()
-                && leaf_ty.is_box()
-            {
-                cx.emit_span_lint(BOX_POINTERS, span, BuiltinBoxPointers { ty });
-            }
-        }
-    }
-}
-
-impl<'tcx> LateLintPass<'tcx> for BoxPointers {
-    fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
-        match it.kind {
-            hir::ItemKind::Fn(..)
-            | hir::ItemKind::TyAlias(..)
-            | hir::ItemKind::Enum(..)
-            | hir::ItemKind::Struct(..)
-            | hir::ItemKind::Union(..) => self.check_heap_type(
-                cx,
-                it.span,
-                cx.tcx.type_of(it.owner_id).instantiate_identity(),
-            ),
-            _ => (),
-        }
-
-        // If it's a struct, we also have to check the fields' types
-        match it.kind {
-            hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
-                for field in struct_def.fields() {
-                    self.check_heap_type(
-                        cx,
-                        field.span,
-                        cx.tcx.type_of(field.def_id).instantiate_identity(),
-                    );
-                }
-            }
-            _ => (),
-        }
-    }
-
-    fn check_expr(&mut self, cx: &LateContext<'_>, e: &hir::Expr<'_>) {
-        let ty = cx.typeck_results().node_type(e.hir_id);
-        self.check_heap_type(cx, e.span, ty);
-    }
-}
-
-declare_lint! {
     /// The `non_shorthand_field_patterns` lint detects using `Struct { x: x }`
     /// instead of `Struct { x }` in a pattern.
     ///
@@ -1640,7 +1565,6 @@ declare_lint_pass!(
     /// which are used by other parts of the compiler.
     SoftLints => [
         WHILE_TRUE,
-        BOX_POINTERS,
         NON_SHORTHAND_FIELD_PATTERNS,
         UNSAFE_CODE,
         MISSING_DOCS,
diff --git a/compiler/rustc_lint/src/lib.rs b/compiler/rustc_lint/src/lib.rs
index 7dae2de7bfb..17f9d4421ae 100644
--- a/compiler/rustc_lint/src/lib.rs
+++ b/compiler/rustc_lint/src/lib.rs
@@ -187,7 +187,6 @@ late_lint_methods!(
             ImproperCTypesDefinitions: ImproperCTypesDefinitions,
             InvalidFromUtf8: InvalidFromUtf8,
             VariantSizeDifferences: VariantSizeDifferences,
-            BoxPointers: BoxPointers,
             PathStatements: PathStatements,
             LetUnderscore: LetUnderscore,
             InvalidReferenceCasting: InvalidReferenceCasting,
@@ -551,6 +550,10 @@ fn register_builtins(store: &mut LintStore) {
         "converted into hard error, see RFC #3535 \
          <https://rust-lang.github.io/rfcs/3535-constants-in-patterns.html> for more information",
     );
+    store.register_removed(
+        "box_pointers",
+        "it does not detect other kinds of allocations, and existed only for historical reasons",
+    );
 }
 
 fn register_internals(store: &mut LintStore) {
diff --git a/compiler/rustc_lint/src/lints.rs b/compiler/rustc_lint/src/lints.rs
index 14084405d0e..7c5640f5959 100644
--- a/compiler/rustc_lint/src/lints.rs
+++ b/compiler/rustc_lint/src/lints.rs
@@ -67,12 +67,6 @@ pub struct BuiltinWhileTrue {
 }
 
 #[derive(LintDiagnostic)]
-#[diag(lint_builtin_box_pointers)]
-pub struct BuiltinBoxPointers<'a> {
-    pub ty: Ty<'a>,
-}
-
-#[derive(LintDiagnostic)]
 #[diag(lint_builtin_non_shorthand_field_patterns)]
 pub struct BuiltinNonShorthandFieldPatterns {
     pub ident: Ident,