Remove some unnecessary check logic for lang items in HIR typeck

Author: compiler-errors

compiler/rustc_hir_typeck/messages.ftl

@@ -96,9 +96,6 @@ hir_typeck_lossy_provenance_ptr2int =
 hir_typeck_method_call_on_unknown_raw_pointee =
     cannot call a method on a raw pointer with an unknown pointee type
 
-hir_typeck_missing_fn_lang_items = failed to find an overloaded call trait for closure call
-    .help = make sure the `fn`/`fn_mut`/`fn_once` lang items are defined and have correctly defined `call`/`call_mut`/`call_once` methods
-
 hir_typeck_missing_parentheses_in_range = can't call method `{$method_name}` on type `{$ty_str}`
 
 hir_typeck_no_associated_item = no {$item_kind} named `{$item_name}` found for {$ty_prefix} `{$ty_str}`{$trait_missing_method ->
@@ -108,8 +105,6 @@ hir_typeck_no_associated_item = no {$item_kind} named `{$item_name}` found for {
 
 hir_typeck_note_edition_guide = for more on editions, read https://doc.rust-lang.org/edition-guide
 
-hir_typeck_op_trait_generic_params = `{$method_name}` must not have any generic parameters
-
 hir_typeck_option_result_asref = use `{$def_path}::as_ref` to convert `{$expected_ty}` to `{$expr_ty}`
 hir_typeck_option_result_cloned = use `{$def_path}::cloned` to clone the value inside the `{$def_path}`
 hir_typeck_option_result_copied = use `{$def_path}::copied` to copy the value inside the `{$def_path}`

compiler/rustc_hir_typeck/src/callee.rs

@@ -253,28 +253,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 adjusted_ty,
                 opt_input_type.as_ref().map(slice::from_ref),
             ) {
-                // Check for `self` receiver on the method, otherwise we can't use this as a `Fn*` trait.
-                if !self.tcx.associated_item(ok.value.def_id).fn_has_self_parameter {
-                    self.dcx().span_delayed_bug(
-                        call_expr.span,
-                        "input to overloaded call fn is not a self receiver",
-                    );
-                    return None;
-                }
-
                 let method = self.register_infer_ok_obligations(ok);
                 let mut autoref = None;
                 if borrow {
                     // Check for &self vs &mut self in the method signature. Since this is either
                     // the Fn or FnMut trait, it should be one of those.
                     let ty::Ref(region, _, mutbl) = method.sig.inputs()[0].kind() else {
-                        // The `fn`/`fn_mut` lang item is ill-formed, which should have
-                        // caused an error elsewhere.
-                        self.dcx().span_delayed_bug(
-                            call_expr.span,
-                            "input to call/call_mut is not a ref",
-                        );
-                        return None;
+                        bug!("Expected `FnMut`/`Fn` to take receiver by-ref/by-mut")
                     };
 
                     // For initial two-phase borrow
@@ -948,9 +933,11 @@ impl<'a, 'tcx> DeferredCallResolution<'tcx> {
                 );
             }
             None => {
-                // This can happen if `#![no_core]` is used and the `fn/fn_mut/fn_once`
-                // lang items are not defined (issue #86238).
-                fcx.dcx().emit_err(errors::MissingFnLangItems { span: self.call_expr.span });
+                span_bug!(
+                    call_expr.span,
+                    "Expected to find a suitable `Fn`/`FnMut`/`FnOnce` implementation for `{}`",
+                    self.adjusted_ty
+                )
             }
         }
     }

compiler/rustc_hir_typeck/src/check.rs

@@ -152,26 +152,22 @@ pub(super) fn check_fn<'a, 'tcx>(
 }
 
 fn check_panic_info_fn(tcx: TyCtxt<'_>, fn_id: LocalDefId, fn_sig: ty::FnSig<'_>) {
+    let span = tcx.def_span(fn_id);
+
     let DefKind::Fn = tcx.def_kind(fn_id) else {
-        let span = tcx.def_span(fn_id);
         tcx.dcx().span_err(span, "should be a function");
         return;
     };
 
     let generic_counts = tcx.generics_of(fn_id).own_counts();
     if generic_counts.types != 0 {
-        let span = tcx.def_span(fn_id);
         tcx.dcx().span_err(span, "should have no type parameters");
     }
     if generic_counts.consts != 0 {
-        let span = tcx.def_span(fn_id);
         tcx.dcx().span_err(span, "should have no const parameters");
     }
 
-    let Some(panic_info_did) = tcx.lang_items().panic_info() else {
-        tcx.dcx().err("language item required, but not found: `panic_info`");
-        return;
-    };
+    let panic_info_did = tcx.require_lang_item(hir::LangItem::PanicInfo, Some(span));
 
     // build type `for<'a, 'b> fn(&'a PanicInfo<'b>) -> !`
     let panic_info_ty = tcx.type_of(panic_info_did).instantiate(
@@ -203,11 +199,7 @@ fn check_panic_info_fn(tcx: TyCtxt<'_>, fn_id: LocalDefId, fn_sig: ty::FnSig<'_>
 
     let _ = check_function_signature(
         tcx,
-        ObligationCause::new(
-            tcx.def_span(fn_id),
-            fn_id,
-            ObligationCauseCode::LangFunctionType(sym::panic_impl),
-        ),
+        ObligationCause::new(span, fn_id, ObligationCauseCode::LangFunctionType(sym::panic_impl)),
         fn_id.into(),
         expected_sig,
     );

compiler/rustc_hir_typeck/src/errors.rs

@@ -83,14 +83,6 @@ pub struct MethodCallOnUnknownRawPointee {
     pub span: Span,
 }
 
-#[derive(Diagnostic)]
-#[diag(hir_typeck_missing_fn_lang_items)]
-#[help]
-pub struct MissingFnLangItems {
-    #[primary_span]
-    pub span: Span,
-}
-
 #[derive(Diagnostic)]
 #[diag(hir_typeck_functional_record_update_on_non_struct, code = E0436)]
 pub struct FunctionalRecordUpdateOnNonStruct {
@@ -193,14 +185,6 @@ pub struct AddMissingParenthesesInRange {
     pub right: Span,
 }
 
-#[derive(Diagnostic)]
-#[diag(hir_typeck_op_trait_generic_params)]
-pub struct OpMethodGenericParams {
-    #[primary_span]
-    pub span: Span,
-    pub method_name: String,
-}
-
 pub struct TypeMismatchFruTypo {
     /// Span of the LHS of the range
     pub expr_span: Span,

compiler/rustc_hir_typeck/src/lib.rs

@@ -444,15 +444,6 @@ fn fatally_break_rust(tcx: TyCtxt<'_>, span: Span) -> ! {
     diag.emit()
 }
 
-/// `expected` here is the expected number of explicit generic arguments on the trait.
-fn has_expected_num_generic_args(tcx: TyCtxt<'_>, trait_did: DefId, expected: usize) -> bool {
-    let generics = tcx.generics_of(trait_did);
-    generics.count()
-        == expected
-            + if generics.has_self { 1 } else { 0 }
-            + if generics.host_effect_index.is_some() { 1 } else { 0 }
-}
-
 pub fn provide(providers: &mut Providers) {
     method::provide(providers);
     *providers = Providers {

compiler/rustc_hir_typeck/src/method/mod.rs

@@ -10,7 +10,6 @@ mod suggest;
 pub use self::suggest::SelfSource;
 pub use self::MethodError::*;
 
-use crate::errors::OpMethodGenericParams;
 use crate::FnCtxt;
 use rustc_errors::{Applicability, Diagnostic, SubdiagnosticMessage};
 use rustc_hir as hir;
@@ -385,26 +384,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // type parameters or early-bound regions.
         let tcx = self.tcx;
         let Some(method_item) = self.associated_value(trait_def_id, m_name) else {
-            tcx.dcx().span_delayed_bug(
-                obligation.cause.span,
-                "operator trait does not have corresponding operator method",
-            );
-            return None;
+            bug!("expected associated item for operator trait")
         };
 
-        if method_item.kind != ty::AssocKind::Fn {
-            self.dcx().span_delayed_bug(tcx.def_span(method_item.def_id), "not a method");
-            return None;
-        }
-
         let def_id = method_item.def_id;
-        let generics = tcx.generics_of(def_id);
-
-        if generics.params.len() != 0 {
-            tcx.dcx().emit_fatal(OpMethodGenericParams {
-                span: tcx.def_span(method_item.def_id),
-                method_name: m_name.to_string(),
-            });
+        if method_item.kind != ty::AssocKind::Fn {
+            span_bug!(tcx.def_span(def_id), "expected `{m_name}` to be an associated function");
         }
 
         debug!("lookup_in_trait_adjusted: method_item={:?}", method_item);

compiler/rustc_hir_typeck/src/op.rs

@@ -1,7 +1,7 @@
 //! Code related to processing overloaded binary and unary operators.
 
 use super::method::MethodCallee;
-use super::{has_expected_num_generic_args, FnCtxt};
+use super::FnCtxt;
 use crate::Expectation;
 use rustc_ast as ast;
 use rustc_data_structures::packed::Pu128;
@@ -887,25 +887,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             lhs_ty, op, opname, trait_did
         );
 
-        // Catches cases like #83893, where a lang item is declared with the
-        // wrong number of generic arguments. Should have yielded an error
-        // elsewhere by now, but we have to catch it here so that we do not
-        // index `other_tys` out of bounds (if the lang item has too many
-        // generic arguments, `other_tys` is too short).
-        if !has_expected_num_generic_args(
-            self.tcx,
-            trait_did,
-            match op {
-                // Binary ops have a generic right-hand side, unary ops don't
-                Op::Binary(..) => 1,
-                Op::Unary(..) => 0,
-            },
-        ) {
-            self.dcx()
-                .span_delayed_bug(span, "operator didn't have the right number of generic args");
-            return Err(vec![]);
-        }
-
         let opname = Ident::with_dummy_span(opname);
         let (opt_rhs_expr, opt_rhs_ty) = opt_rhs.unzip();
         let input_types = opt_rhs_ty.as_slice();

compiler/rustc_hir_typeck/src/place_op.rs

@@ -1,5 +1,5 @@
 use crate::method::MethodCallee;
-use crate::{has_expected_num_generic_args, FnCtxt, PlaceOp};
+use crate::{FnCtxt, PlaceOp};
 use rustc_ast as ast;
 use rustc_errors::Applicability;
 use rustc_hir as hir;
@@ -209,20 +209,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             return None;
         };
 
-        // If the lang item was declared incorrectly, stop here so that we don't
-        // run into an ICE (#83893). The error is reported where the lang item is
-        // declared.
-        if !has_expected_num_generic_args(
-            self.tcx,
-            imm_tr,
-            match op {
-                PlaceOp::Deref => 0,
-                PlaceOp::Index => 1,
-            },
-        ) {
-            return None;
-        }
-
         self.lookup_method_in_trait(
             self.misc(span),
             Ident::with_dummy_span(imm_op),
@@ -249,20 +235,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             return None;
         };
 
-        // If the lang item was declared incorrectly, stop here so that we don't
-        // run into an ICE (#83893). The error is reported where the lang item is
-        // declared.
-        if !has_expected_num_generic_args(
-            self.tcx,
-            mut_tr,
-            match op {
-                PlaceOp::Deref => 0,
-                PlaceOp::Index => 1,
-            },
-        ) {
-            return None;
-        }
-
         self.lookup_method_in_trait(
             self.misc(span),
             Ident::with_dummy_span(mut_op),