Remove possibly footgunny is_const method

Author: oli-obk

compiler/rustc_hir/src/hir.rs

@@ -4593,10 +4593,6 @@ impl FnHeader {
         matches!(self.asyncness, IsAsync::Async(_))
     }
 
-    pub fn is_const(&self) -> bool {
-        matches!(self.constness, Constness::Const { .. })
-    }
-
     pub fn is_unsafe(&self) -> bool {
         self.safety().is_unsafe()
     }

compiler/rustc_passes/src/stability.rs

@@ -12,9 +12,9 @@ use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::{CRATE_DEF_ID, LOCAL_CRATE, LocalDefId, LocalModDefId};
 use rustc_hir::intravisit::{self, Visitor, VisitorExt};
 use rustc_hir::{
-    self as hir, AmbigArg, ConstStability, DefaultBodyStability, FieldDef, HirId, Item, ItemKind,
-    Path, Stability, StabilityLevel, StableSince, TraitRef, Ty, TyKind, UnstableReason, UsePath,
-    VERSION_PLACEHOLDER, Variant, find_attr,
+    self as hir, AmbigArg, ConstStability, Constness, DefaultBodyStability, FieldDef, HirId, Item,
+    ItemKind, Path, Stability, StabilityLevel, StableSince, TraitRef, Ty, TyKind, UnstableReason,
+    UsePath, VERSION_PLACEHOLDER, Variant, find_attr,
 };
 use rustc_middle::hir::nested_filter;
 use rustc_middle::middle::lib_features::{FeatureStability, LibFeatures};
@@ -207,7 +207,7 @@ fn lookup_const_stability(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Option<ConstSt
             let parent_stab = tcx.lookup_stability(parent)?;
             if parent_stab.is_unstable()
                 && let Some(fn_sig) = tcx.hir_node_by_def_id(def_id).fn_sig()
-                && fn_sig.header.is_const()
+                && matches!(fn_sig.header.constness, Constness::Const { .. })
             {
                 let const_stable_indirect = find_attr!(tcx, def_id, RustcConstStableIndirect);
                 return Some(ConstStability::unmarked(const_stable_indirect, parent_stab));
@@ -229,7 +229,7 @@ fn lookup_const_stability(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Option<ConstSt
     // If this is a const fn but not annotated with stability markers, see if we can inherit
     // regular stability.
     if let Some(fn_sig) = tcx.hir_node_by_def_id(def_id).fn_sig()
-        && fn_sig.header.is_const()
+        && matches!(fn_sig.header.constness, Constness::Const { .. })
         && const_stab.is_none()
         // We only ever inherit unstable features.
         && let Some(inherit_regular_stab) = tcx.lookup_stability(def_id)
@@ -385,7 +385,7 @@ impl<'tcx> MissingStabilityAnnotations<'tcx> {
         // implied), check if the function/method is const or the parent impl block is const.
         let fn_sig = self.tcx.hir_node_by_def_id(def_id).fn_sig();
         if let Some(fn_sig) = fn_sig
-            && !fn_sig.header.is_const()
+            && !matches!(fn_sig.header.constness, Constness::Const { .. })
             && const_stab.is_some()
             && find_attr_span!(RustcConstStability).is_some()
         {

src/librustdoc/json/conversions.rs

@@ -409,7 +409,7 @@ impl FromClean<rustc_hir::FnHeader> for FunctionHeader {
         };
         FunctionHeader {
             is_async: header.is_async(),
-            is_const: header.is_const(),
+            is_const: matches!(header.constness, rustc_hir::Constness::Const { .. }),
             is_unsafe,
             abi: header.abi.into_json(renderer),
         }

src/tools/clippy/clippy_lints/src/derivable_impls.rs

@@ -253,7 +253,7 @@ impl<'tcx> LateLintPass<'tcx> for DerivableImpls {
             && !attrs.iter().any(|attr| attr.doc_str().is_some())
             && cx.tcx.hir_attrs(impl_item_hir).is_empty()
         {
-            let is_const = constness == hir::Constness::Const;
+            let is_const = matches!(constness, hir::Constness::Const { always: false });
             if adt_def.is_struct() {
                 check_struct(
                     cx,

src/tools/clippy/clippy_lints/src/methods/should_implement_trait.rs

@@ -29,7 +29,7 @@ pub(super) fn check_impl_item<'tcx>(
         && first_arg_ty_opt
             .is_none_or(|first_arg_ty| method_config.self_kind.matches(cx, self_ty, first_arg_ty))
         && sig.header.is_safe()
-        && !sig.header.is_const()
+        && matches!(sig.header.constness, hir::Constness::NotConst)
         && !sig.header.is_async()
         && sig.header.abi == ExternAbi::Rust
         && method_config.lifetime_param_cond(impl_item)

src/tools/clippy/clippy_lints/src/missing_const_for_fn.rs

@@ -187,7 +187,7 @@ impl<'tcx> LateLintPass<'tcx> for MissingConstForFn {
 // We don't have to lint on something that's already `const`
 #[must_use]
 fn already_const(header: hir::FnHeader) -> bool {
-    header.constness == Constness::Const
+    matches!(header.constness, Constness::Const { .. })
 }
 
 fn could_be_const_with_abi(cx: &LateContext<'_>, msrv: Msrv, abi: ExternAbi) -> bool {

src/tools/clippy/clippy_utils/src/check_proc_macro.rs

@@ -242,7 +242,7 @@ fn expr_search_pat(tcx: TyCtxt<'_>, e: &Expr<'_>) -> (Pat, Pat) {
 fn fn_header_search_pat(header: FnHeader) -> Pat {
     if header.is_async() {
         Pat::Str("async")
-    } else if header.is_const() {
+    } else if matches!(header.constness, rustc_hir::Constness::Const { always: false }) {
         Pat::Str("const")
     } else if header.is_unsafe() {
         Pat::Str("unsafe")