Remove a dead early lint

Dropped in favor a hard error in RUST-127907.

Author: fmease

compiler/rustc_lint/messages.ftl

@@ -181,9 +181,6 @@ lint_builtin_unused_doc_comment = unused doc comment
 lint_builtin_while_true = denote infinite loops with `loop {"{"} ... {"}"}`
     .suggestion = use `loop`
 
-lint_byte_slice_in_packed_struct_with_derive = {$ty} slice in a packed struct that derives a built-in trait
-    .help = consider implementing the trait by hand, or remove the `packed` attribute
-
 lint_check_name_unknown_tool = unknown lint tool: `{$tool_name}`
 
 lint_closure_returning_async_block = closure returning async block can be made into an async closure

compiler/rustc_lint/src/early/diagnostics.rs

@@ -270,9 +270,6 @@ pub fn decorate_builtin_lint(
             }
             .decorate_lint(diag);
         }
-        BuiltinLintDiag::ByteSliceInPackedStructWithDerive { ty } => {
-            lints::ByteSliceInPackedStructWithDerive { ty }.decorate_lint(diag);
-        }
         BuiltinLintDiag::ExternCrateNotIdiomatic { vis_span, ident_span } => {
             let suggestion_span = vis_span.between(ident_span);
             let code = if vis_span.is_empty() { "use " } else { " use " };

compiler/rustc_lint/src/lints.rs

@@ -2910,14 +2910,6 @@ pub(crate) struct NamedArgumentUsedPositionally {
     pub named_arg_name: String,
 }
 
-#[derive(LintDiagnostic)]
-#[diag(lint_byte_slice_in_packed_struct_with_derive)]
-#[help]
-pub(crate) struct ByteSliceInPackedStructWithDerive {
-    // FIXME: make this translatable
-    pub ty: String,
-}
-
 #[derive(LintDiagnostic)]
 #[diag(lint_extern_crate_not_idiomatic)]
 pub(crate) struct ExternCrateNotIdiomatic {

compiler/rustc_lint_defs/src/lib.rs

@@ -690,10 +690,6 @@ pub enum BuiltinLintDiag {
         /// Indicates if the named argument is used as a width/precision for formatting
         is_formatting_arg: bool,
     },
-    ByteSliceInPackedStructWithDerive {
-        // FIXME: enum of byte/string
-        ty: String,
-    },
     ExternCrateNotIdiomatic {
         vis_span: Span,
         ident_span: Span,