Auto merge of rust-lang#10164 - khuey:default_enum_unit_variant_msrv, r=llogiq

Restrict suggestion of deriving Default for enums to MSRV 1.62.

See https://blog.rust-lang.org/2022/06/30/Rust-1.62.0.html#default-enum-variants

---

changelog: none

Author: bors

clippy_lints/src/derivable_impls.rs

@@ -1,4 +1,5 @@
 use clippy_utils::diagnostics::span_lint_and_then;
+use clippy_utils::msrvs::{self, Msrv};
 use clippy_utils::source::indent_of;
 use clippy_utils::{is_default_equivalent, peel_blocks};
 use rustc_errors::Applicability;
@@ -8,7 +9,7 @@ use rustc_hir::{
 };
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::ty::{AdtDef, DefIdTree};
-use rustc_session::{declare_lint_pass, declare_tool_lint};
+use rustc_session::{declare_tool_lint, impl_lint_pass};
 use rustc_span::sym;
 
 declare_clippy_lint! {
@@ -53,7 +54,18 @@ declare_clippy_lint! {
     "manual implementation of the `Default` trait which is equal to a derive"
 }
 
-declare_lint_pass!(DerivableImpls => [DERIVABLE_IMPLS]);
+pub struct DerivableImpls {
+    msrv: Msrv,
+}
+
+impl DerivableImpls {
+    #[must_use]
+    pub fn new(msrv: Msrv) -> Self {
+        DerivableImpls { msrv }
+    }
+}
+
+impl_lint_pass!(DerivableImpls => [DERIVABLE_IMPLS]);
 
 fn is_path_self(e: &Expr<'_>) -> bool {
     if let ExprKind::Path(QPath::Resolved(_, p)) = e.kind {
@@ -181,10 +193,12 @@ impl<'tcx> LateLintPass<'tcx> for DerivableImpls {
             then {
                 if adt_def.is_struct() {
                     check_struct(cx, item, self_ty, func_expr, adt_def);
-                } else if adt_def.is_enum() {
+                } else if adt_def.is_enum() && self.msrv.meets(msrvs::DEFAULT_ENUM_ATTRIBUTE) {
                     check_enum(cx, item, func_expr, adt_def);
                 }
             }
         }
     }
+
+    extract_msrv_attr!(LateContext);
 }

clippy_lints/src/lib.rs

@@ -639,7 +639,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
     store.register_late_pass(|_| Box::new(panic_unimplemented::PanicUnimplemented));
     store.register_late_pass(|_| Box::new(strings::StringLitAsBytes));
     store.register_late_pass(|_| Box::new(derive::Derive));
-    store.register_late_pass(|_| Box::new(derivable_impls::DerivableImpls));
+    store.register_late_pass(move |_| Box::new(derivable_impls::DerivableImpls::new(msrv())));
     store.register_late_pass(|_| Box::new(drop_forget_ref::DropForgetRef));
     store.register_late_pass(|_| Box::new(empty_enum::EmptyEnum));
     store.register_late_pass(|_| Box::new(invalid_upcast_comparisons::InvalidUpcastComparisons));

clippy_utils/src/msrvs.rs

@@ -20,8 +20,9 @@ macro_rules! msrv_aliases {
 // names may refer to stabilized feature flags or library items
 msrv_aliases! {
     1,65,0 { LET_ELSE }
-    1,62,0 { BOOL_THEN_SOME }
+    1,62,0 { BOOL_THEN_SOME, DEFAULT_ENUM_ATTRIBUTE }
     1,58,0 { FORMAT_ARGS_CAPTURE, PATTERN_TRAIT_CHAR_ARRAY }
+    1,55,0 { SEEK_REWIND }
     1,53,0 { OR_PATTERNS, MANUAL_BITS, BTREE_MAP_RETAIN, BTREE_SET_RETAIN, ARRAY_INTO_ITERATOR }
     1,52,0 { STR_SPLIT_ONCE, REM_EUCLID_CONST }
     1,51,0 { BORROW_AS_PTR, SEEK_FROM_CURRENT, UNSIGNED_ABS }
@@ -45,7 +46,6 @@ msrv_aliases! {
     1,18,0 { HASH_MAP_RETAIN, HASH_SET_RETAIN }
     1,17,0 { FIELD_INIT_SHORTHAND, STATIC_IN_CONST, EXPECT_ERR }
     1,16,0 { STR_REPEAT }
-    1,55,0 { SEEK_REWIND }
 }
 
 fn parse_msrv(msrv: &str, sess: Option<&Session>, span: Option<Span>) -> Option<RustcVersion> {