Improve ICE messages for `*::expect_*`

1 files changed, 69 insertions, 49 deletions

diff --git a/compiler/rustc_hir/src/hir.rs b/compiler/rustc_hir/src/hir.rs
index 4640317ac73..ef4a8754ac2 100644
--- a/compiler/rustc_hir/src/hir.rs
+++ b/compiler/rustc_hir/src/hir.rs
@@ -2277,23 +2277,28 @@ impl<'hir> TraitItem<'hir> {
     /// Expect an [`TraitItemKind::Const`] or panic.
     #[track_caller]
     pub fn expect_const(&self) -> (&'hir Ty<'hir>, Option<BodyId>) {
-        let TraitItemKind::Const(ty, body) = self.kind else { unreachable!() };
+        let TraitItemKind::Const(ty, body) = self.kind else { self.expect_failed("a constant") };
         (ty, body)
     }
 
     /// Expect an [`TraitItemKind::Fn`] or panic.
     #[track_caller]
     pub fn expect_fn(&self) -> (&FnSig<'hir>, &TraitFn<'hir>) {
-        let TraitItemKind::Fn(ty, trfn) = &self.kind else { unreachable!() };
+        let TraitItemKind::Fn(ty, trfn) = &self.kind else { self.expect_failed("a function") };
         (ty, trfn)
     }
 
     /// Expect an [`TraitItemKind::ExternCrate`] or panic.
     #[track_caller]
     pub fn expect_type(&self) -> (GenericBounds<'hir>, Option<&'hir Ty<'hir>>) {
-        let TraitItemKind::Type(bounds, ty) = self.kind else { unreachable!() };
+        let TraitItemKind::Type(bounds, ty) = self.kind else { self.expect_failed("a type") };
         (bounds, ty)
     }
+
+    #[track_caller]
+    fn expect_failed(&self, expected: &'static str) -> ! {
+        panic!("expected {expected} item, found {self:?}")
+    }
 }
 
 /// Represents a trait method's body (or just argument names).
@@ -2360,23 +2365,28 @@ impl<'hir> ImplItem<'hir> {
     /// Expect an [`ImplItemKind::Const`] or panic.
     #[track_caller]
     pub fn expect_const(&self) -> (&'hir Ty<'hir>, BodyId) {
-        let ImplItemKind::Const(ty, body) = self.kind else { unreachable!() };
+        let ImplItemKind::Const(ty, body) = self.kind else { self.expect_failed("a constant") };
         (ty, body)
     }
 
     /// Expect an [`ImplItemKind::Fn`] or panic.
     #[track_caller]
     pub fn expect_fn(&self) -> (&FnSig<'hir>, BodyId) {
-        let ImplItemKind::Fn(ty, body) = &self.kind else { unreachable!() };
+        let ImplItemKind::Fn(ty, body) = &self.kind else { self.expect_failed("a function") };
         (ty, *body)
     }
 
-    /// Expect an [`ImplItemKind::ExternCrate`] or panic.
+    /// Expect an [`ImplItemKind::Type`] or panic.
     #[track_caller]
     pub fn expect_type(&self) -> &'hir Ty<'hir> {
-        let ImplItemKind::Type(ty) = self.kind else { unreachable!() };
+        let ImplItemKind::Type(ty) = self.kind else { self.expect_failed("a type") };
         ty
     }
+
+    #[track_caller]
+    fn expect_failed(&self, expected: &'static str) -> ! {
+        panic!("expected {expected} item, found {self:?}")
+    }
 }
 
 /// Represents various kinds of content within an `impl`.
@@ -3051,68 +3061,68 @@ impl<'hir> Item<'hir> {
     /// Expect an [`ItemKind::ExternCrate`] or panic.
     #[track_caller]
     pub fn expect_extern_crate(&self) -> Option<Symbol> {
-        let ItemKind::ExternCrate(s) = self.kind else { unreachable!() };
+        let ItemKind::ExternCrate(s) = self.kind else { self.expect_failed("an extern crate") };
         s
     }
 
     /// Expect an [`ItemKind::Use`] or panic.
     #[track_caller]
     pub fn expect_use(&self) -> (&'hir UsePath<'hir>, UseKind) {
-        let ItemKind::Use(p, uk) = self.kind else { unreachable!() };
+        let ItemKind::Use(p, uk) = self.kind else { self.expect_failed("a use") };
         (p, uk)
     }
 
     /// Expect an [`ItemKind::Static`] or panic.
     #[track_caller]
     pub fn expect_static(&self) -> (&'hir Ty<'hir>, Mutability, BodyId) {
-        let ItemKind::Static(ty, mutbl, body) = self.kind else { unreachable!() };
+        let ItemKind::Static(ty, mutbl, body) = self.kind else { self.expect_failed("a static") };
         (ty, mutbl, body)
     }
     /// Expect an [`ItemKind::Const`] or panic.
     #[track_caller]
     pub fn expect_const(&self) -> (&'hir Ty<'hir>, BodyId) {
-        let ItemKind::Const(ty, body) = self.kind else { unreachable!() };
+        let ItemKind::Const(ty, body) = self.kind else { self.expect_failed("a constant") };
         (ty, body)
     }
     /// Expect an [`ItemKind::Fn`] or panic.
     #[track_caller]
     pub fn expect_fn(&self) -> (&FnSig<'hir>, &'hir Generics<'hir>, BodyId) {
-        let ItemKind::Fn(sig, gen, body) = &self.kind else { unreachable!() };
+        let ItemKind::Fn(sig, gen, body) = &self.kind else { self.expect_failed("a function") };
         (sig, gen, *body)
     }
 
     /// Expect an [`ItemKind::Macro`] or panic.
     #[track_caller]
     pub fn expect_macro(&self) -> (&ast::MacroDef, MacroKind) {
-        let ItemKind::Macro(def, mk) = &self.kind else { unreachable!() };
+        let ItemKind::Macro(def, mk) = &self.kind else { self.expect_failed("a macro") };
         (def, *mk)
     }
 
     /// Expect an [`ItemKind::Mod`] or panic.
     #[track_caller]
     pub fn expect_mod(&self) -> &'hir Mod<'hir> {
-        let ItemKind::Mod(m) = self.kind else { unreachable!() };
+        let ItemKind::Mod(m) = self.kind else { self.expect_failed("a module") };
         m
     }
 
     /// Expect an [`ItemKind::ForeignMod`] or panic.
     #[track_caller]
     pub fn expect_foreign_mod(&self) -> (Abi, &'hir [ForeignItemRef]) {
-        let ItemKind::ForeignMod { abi, items } = self.kind else { unreachable!() };
+        let ItemKind::ForeignMod { abi, items } = self.kind else { self.expect_failed("a foreign module") };
         (abi, items)
     }
 
     /// Expect an [`ItemKind::GlobalAsm`] or panic.
     #[track_caller]
     pub fn expect_global_asm(&self) -> &'hir InlineAsm<'hir> {
-        let ItemKind::GlobalAsm(asm) = self.kind else { unreachable!() };
+        let ItemKind::GlobalAsm(asm) = self.kind else { self.expect_failed("a global asm") };
         asm
     }
 
     /// Expect an [`ItemKind::TyAlias`] or panic.
     #[track_caller]
     pub fn expect_ty_alias(&self) -> (&'hir Ty<'hir>, &'hir Generics<'hir>) {
-        let ItemKind::TyAlias(ty, gen) = self.kind else { unreachable!() };
+        let ItemKind::TyAlias(ty, gen) = self.kind else { self.expect_failed("a type alias") };
         (ty, gen)
     }
 
@@ -3120,21 +3130,21 @@ impl<'hir> Item<'hir> {
     /// Expect an [`ItemKind::OpaqueTy`] or panic.
     #[track_caller]
     pub fn expect_opaque_ty(&self) -> &OpaqueTy<'hir> {
-        let ItemKind::OpaqueTy(ty) = &self.kind else { unreachable!() };
+        let ItemKind::OpaqueTy(ty) = &self.kind else { self.expect_failed("an opaque type") };
         ty
     }
 
     /// Expect an [`ItemKind::Enum`] or panic.
     #[track_caller]
     pub fn expect_enum(&self) -> (&EnumDef<'hir>, &'hir Generics<'hir>) {
-        let ItemKind::Enum(def, gen) = &self.kind else { unreachable!() };
+        let ItemKind::Enum(def, gen) = &self.kind else { self.expect_failed("an enum") };
         (def, gen)
     }
 
     /// Expect an [`ItemKind::Struct`] or panic.
     #[track_caller]
     pub fn expect_struct(&self) -> (&VariantData<'hir>, &'hir Generics<'hir>) {
-        let ItemKind::Struct(data, gen) = &self.kind else { unreachable!() };
+        let ItemKind::Struct(data, gen) = &self.kind else { self.expect_failed("a struct") };
         (data, gen)
     }
 
@@ -3142,7 +3152,7 @@ impl<'hir> Item<'hir> {
     /// Expect an [`ItemKind::Union`] or panic.
     #[track_caller]
     pub fn expect_union(&self) -> (&VariantData<'hir>, &'hir Generics<'hir>) {
-        let ItemKind::Union(data, gen) = &self.kind else { unreachable!() };
+        let ItemKind::Union(data, gen) = &self.kind else { self.expect_failed("a union") };
         (data, gen)
     }
 
@@ -3151,23 +3161,28 @@ impl<'hir> Item<'hir> {
     pub fn expect_trait(
         self,
     ) -> (IsAuto, Unsafety, &'hir Generics<'hir>, GenericBounds<'hir>, &'hir [TraitItemRef]) {
-        let ItemKind::Trait(is_auto, unsafety, gen, bounds, items) = self.kind else { unreachable!() };
+        let ItemKind::Trait(is_auto, unsafety, gen, bounds, items) = self.kind else { self.expect_failed("a trait") };
         (is_auto, unsafety, gen, bounds, items)
     }
 
     /// Expect an [`ItemKind::TraitAlias`] or panic.
     #[track_caller]
     pub fn expect_trait_alias(&self) -> (&'hir Generics<'hir>, GenericBounds<'hir>) {
-        let ItemKind::TraitAlias(gen, bounds) = self.kind else { unreachable!() };
+        let ItemKind::TraitAlias(gen, bounds) = self.kind else { self.expect_failed("a trait alias") };
         (gen, bounds)
     }
 
     /// Expect an [`ItemKind::Impl`] or panic.
     #[track_caller]
     pub fn expect_impl(&self) -> &'hir Impl<'hir> {
-        let ItemKind::Impl(imp) = self.kind else { unreachable!() };
+        let ItemKind::Impl(imp) = self.kind else { self.expect_failed("an impl") };
         imp
     }
+
+    #[track_caller]
+    fn expect_failed(&self, expected: &'static str) -> ! {
+        panic!("expected {expected} item, found {self:?}")
+    }
 }
 
 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
@@ -3757,176 +3772,181 @@ impl<'hir> Node<'hir> {
     /// Expect a [`Node::Param`] or panic.
     #[track_caller]
     pub fn expect_param(self) -> &'hir Param<'hir> {
-        let Node::Param(this) = self else { unreachable!() };
+        let Node::Param(this) = self else { self.expect_failed("a parameter") };
         this
     }
 
     /// Expect a [`Node::Item`] or panic.
     #[track_caller]
     pub fn expect_item(self) -> &'hir Item<'hir> {
-        let Node::Item(this) = self else { unreachable!() };
+        let Node::Item(this) = self else { self.expect_failed("a item") };
         this
     }
 
     /// Expect a [`Node::ForeignItem`] or panic.
     #[track_caller]
     pub fn expect_foreign_item(self) -> &'hir ForeignItem<'hir> {
-        let Node::ForeignItem(this) = self else { unreachable!() };
+        let Node::ForeignItem(this) = self else { self.expect_failed("a foreign item") };
         this
     }
 
     /// Expect a [`Node::TraitItem`] or panic.
     #[track_caller]
     pub fn expect_trait_item(self) -> &'hir TraitItem<'hir> {
-        let Node::TraitItem(this) = self else { unreachable!() };
+        let Node::TraitItem(this) = self else { self.expect_failed("a trait item") };
         this
     }
 
     /// Expect a [`Node::ImplItem`] or panic.
     #[track_caller]
     pub fn expect_impl_item(self) -> &'hir ImplItem<'hir> {
-        let Node::ImplItem(this) = self else { unreachable!() };
+        let Node::ImplItem(this) = self else { self.expect_failed("an implementation item") };
         this
     }
 
     /// Expect a [`Node::Variant`] or panic.
     #[track_caller]
     pub fn expect_variant(self) -> &'hir Variant<'hir> {
-        let Node::Variant(this) = self else { unreachable!() };
+        let Node::Variant(this) = self else { self.expect_failed("a variant") };
         this
     }
 
     /// Expect a [`Node::Field`] or panic.
     #[track_caller]
     pub fn expect_field(self) -> &'hir FieldDef<'hir> {
-        let Node::Field(this) = self else { unreachable!() };
+        let Node::Field(this) = self else { self.expect_failed("a field definition") };
         this
     }
 
     /// Expect a [`Node::AnonConst`] or panic.
     #[track_caller]
     pub fn expect_anon_const(self) -> &'hir AnonConst {
-        let Node::AnonConst(this) = self else { unreachable!() };
+        let Node::AnonConst(this) = self else { self.expect_failed("an anonymous constant") };
         this
     }
 
     /// Expect a [`Node::Expr`] or panic.
     #[track_caller]
     pub fn expect_expr(self) -> &'hir Expr<'hir> {
-        let Node::Expr(this) = self else { unreachable!() };
+        let Node::Expr(this) = self else { self.expect_failed("an expression") };
         this
     }
     /// Expect a [`Node::ExprField`] or panic.
     #[track_caller]
     pub fn expect_expr_field(self) -> &'hir ExprField<'hir> {
-        let Node::ExprField(this) = self else { unreachable!() };
+        let Node::ExprField(this) = self else { self.expect_failed("an expression field") };
         this
     }
 
     /// Expect a [`Node::Stmt`] or panic.
     #[track_caller]
     pub fn expect_stmt(self) -> &'hir Stmt<'hir> {
-        let Node::Stmt(this) = self else { unreachable!() };
+        let Node::Stmt(this) = self else { self.expect_failed("a statement") };
         this
     }
 
     /// Expect a [`Node::PathSegment`] or panic.
     #[track_caller]
     pub fn expect_path_segment(self) -> &'hir PathSegment<'hir> {
-        let Node::PathSegment(this) = self else { unreachable!() };
+        let Node::PathSegment(this) = self else { self.expect_failed("a path segment") };
         this
     }
 
     /// Expect a [`Node::Ty`] or panic.
     #[track_caller]
     pub fn expect_ty(self) -> &'hir Ty<'hir> {
-        let Node::Ty(this) = self else { unreachable!() };
+        let Node::Ty(this) = self else { self.expect_failed("a type") };
         this
     }
 
     /// Expect a [`Node::TypeBinding`] or panic.
     #[track_caller]
     pub fn expect_type_binding(self) -> &'hir TypeBinding<'hir> {
-        let Node::TypeBinding(this) = self else { unreachable!() };
+        let Node::TypeBinding(this) = self else { self.expect_failed("a type binding") };
         this
     }
 
     /// Expect a [`Node::TraitRef`] or panic.
     #[track_caller]
     pub fn expect_trait_ref(self) -> &'hir TraitRef<'hir> {
-        let Node::TraitRef(this) = self else { unreachable!() };
+        let Node::TraitRef(this) = self else { self.expect_failed("a trait reference") };
         this
     }
 
     /// Expect a [`Node::Pat`] or panic.
     #[track_caller]
     pub fn expect_pat(self) -> &'hir Pat<'hir> {
-        let Node::Pat(this) = self else { unreachable!() };
+        let Node::Pat(this) = self else { self.expect_failed("a pattern") };
         this
     }
 
     /// Expect a [`Node::PatField`] or panic.
     #[track_caller]
     pub fn expect_pat_field(self) -> &'hir PatField<'hir> {
-        let Node::PatField(this) = self else { unreachable!() };
+        let Node::PatField(this) = self else { self.expect_failed("a pattern field") };
         this
     }
 
     /// Expect a [`Node::Arm`] or panic.
     #[track_caller]
     pub fn expect_arm(self) -> &'hir Arm<'hir> {
-        let Node::Arm(this) = self else { unreachable!() };
+        let Node::Arm(this) = self else { self.expect_failed("an arm") };
         this
     }
 
     /// Expect a [`Node::Block`] or panic.
     #[track_caller]
     pub fn expect_block(self) -> &'hir Block<'hir> {
-        let Node::Block(this) = self else { unreachable!() };
+        let Node::Block(this) = self else { self.expect_failed("a block") };
         this
     }
 
     /// Expect a [`Node::Local`] or panic.
     #[track_caller]
     pub fn expect_local(self) -> &'hir Local<'hir> {
-        let Node::Local(this) = self else { unreachable!() };
+        let Node::Local(this) = self else { self.expect_failed("a local") };
         this
     }
 
     /// Expect a [`Node::Ctor`] or panic.
     #[track_caller]
     pub fn expect_ctor(self) -> &'hir VariantData<'hir> {
-        let Node::Ctor(this) = self else { unreachable!() };
+        let Node::Ctor(this) = self else { self.expect_failed("a constructor") };
         this
     }
 
     /// Expect a [`Node::Lifetime`] or panic.
     #[track_caller]
     pub fn expect_lifetime(self) -> &'hir Lifetime {
-        let Node::Lifetime(this) = self else { unreachable!() };
+        let Node::Lifetime(this) = self else { self.expect_failed("a lifetime") };
         this
     }
 
     /// Expect a [`Node::GenericParam`] or panic.
     #[track_caller]
     pub fn expect_generic_param(self) -> &'hir GenericParam<'hir> {
-        let Node::GenericParam(this) = self else { unreachable!() };
+        let Node::GenericParam(this) = self else { self.expect_failed("a generic parameter") };
         this
     }
 
     /// Expect a [`Node::Crate`] or panic.
     #[track_caller]
     pub fn expect_crate(self) -> &'hir Mod<'hir> {
-        let Node::Crate(this) = self else { unreachable!() };
+        let Node::Crate(this) = self else { self.expect_failed("a crate") };
         this
     }
 
     /// Expect a [`Node::Infer`] or panic.
     #[track_caller]
     pub fn expect_infer(self) -> &'hir InferArg {
-        let Node::Infer(this) = self else { unreachable!() };
+        let Node::Infer(this) = self else { self.expect_failed("an infer") };
         this
     }
+
+    #[track_caller]
+    fn expect_failed(&self, expected: &'static str) -> ! {
+        panic!("expected {expected} node, found {self:?}")
+    }
 }
 
 // Some nodes are used a lot. Make sure they don't unintentionally get bigger.