Rollup merge of rust-lang#155031 - aerooneqq:delegation-generic-args-lowering-ice, r=petrochenkov

delegation: fix unelided lifetime ICE, refactoring of GenericArgPosition

This PR does two things:
- First it restores `lower_generic_args_of_path` as it was before rust-lang#151864, as it turns out we should use `GenericArgPosition::Type` for generic args lowering for signature inheritance, as it will not cause lifetime inference and then ICEs during child args lowering,
- Next it refactors `GenericArgPosition` enum replacing `Value` and `MethodCall` with `Call(IsMethodCall)`, as the only place where we created `Value` or `MethodCall` variants was in `check_generic_arg_count_for_call`, where it was a match over `is_method_call`. Not sure it is needed, but seems cleaner to me.

Fixes rust-lang#154178, part of rust-lang#118212.

r? @petrochenkov

Author: JonathanBrouwer

compiler/rustc_hir_analysis/src/delegation.rs

@@ -14,7 +14,7 @@ use rustc_middle::ty::{
 use rustc_span::{ErrorGuaranteed, Span, kw};
 
 use crate::collect::ItemCtxt;
-use crate::hir_ty_lowering::{GenericArgPosition, HirTyLowerer};
+use crate::hir_ty_lowering::HirTyLowerer;
 
 type RemapTable = FxHashMap<u32, u32>;
 
@@ -581,14 +581,7 @@ fn get_delegation_user_specified_args<'tcx>(
         let self_ty = get_delegation_self_ty(tcx, delegation_id);
 
         lowerer
-            .lower_generic_args_of_path(
-                segment.ident.span,
-                def_id,
-                &[],
-                segment,
-                self_ty,
-                GenericArgPosition::Type,
-            )
+            .lower_generic_args_of_path(segment.ident.span, def_id, &[], segment, self_ty)
             .0
             .as_slice()
     });
@@ -610,14 +603,7 @@ fn get_delegation_user_specified_args<'tcx>(
             };
 
             let args = lowerer
-                .lower_generic_args_of_path(
-                    segment.ident.span,
-                    def_id,
-                    parent_args,
-                    segment,
-                    None,
-                    GenericArgPosition::Value,
-                )
+                .lower_generic_args_of_path(segment.ident.span, def_id, parent_args, segment, None)
                 .0;
 
             &args[parent_args.len()..]

compiler/rustc_hir_analysis/src/hir_ty_lowering/generics.rs

@@ -385,17 +385,14 @@ pub fn lower_generic_args<'tcx: 'a, 'a>(
 
 /// Checks that the correct number of generic arguments have been provided.
 /// Used specifically for function calls.
-pub fn check_generic_arg_count_for_call(
+pub fn check_generic_arg_count_for_value_path(
     cx: &dyn HirTyLowerer<'_>,
     def_id: DefId,
     generics: &ty::Generics,
     seg: &hir::PathSegment<'_>,
     is_method_call: IsMethodCall,
 ) -> GenericArgCountResult {
-    let gen_pos = match is_method_call {
-        IsMethodCall::Yes => GenericArgPosition::MethodCall,
-        IsMethodCall::No => GenericArgPosition::Value,
-    };
+    let gen_pos = GenericArgPosition::Value(is_method_call);
     check_generic_arg_count(cx, def_id, seg, generics, gen_pos, generics.has_own_self())
 }
 
@@ -649,7 +646,7 @@ pub(crate) fn prohibit_explicit_late_bound_lifetimes(
         let note = "the late bound lifetime parameter is introduced here";
         let span = args.args[0].span();
 
-        if position == GenericArgPosition::Value
+        if position == GenericArgPosition::Value(IsMethodCall::No)
             && args.num_lifetime_params() != param_counts.lifetimes
         {
             struct_span_code_err!(cx.dcx(), span, E0794, "{}", msg)

compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs

@@ -318,7 +318,7 @@ pub enum ExplicitLateBound {
     No,
 }
 
-#[derive(Copy, Clone, PartialEq)]
+#[derive(Debug, Copy, Clone, PartialEq)]
 pub enum IsMethodCall {
     Yes,
     No,
@@ -329,8 +329,7 @@ pub enum IsMethodCall {
 #[derive(Debug, Copy, Clone, PartialEq)]
 pub(crate) enum GenericArgPosition {
     Type,
-    Value, // e.g., functions
-    MethodCall,
+    Value(IsMethodCall),
 }
 
 /// Whether to allow duplicate associated iten constraints in a trait ref, e.g.
@@ -561,14 +560,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         def_id: DefId,
         item_segment: &hir::PathSegment<'tcx>,
     ) -> GenericArgsRef<'tcx> {
-        let (args, _) = self.lower_generic_args_of_path(
-            span,
-            def_id,
-            &[],
-            item_segment,
-            None,
-            GenericArgPosition::Type,
-        );
+        let (args, _) = self.lower_generic_args_of_path(span, def_id, &[], item_segment, None);
         if let Some(c) = item_segment.args().constraints.first() {
             prohibit_assoc_item_constraint(self, c, Some((def_id, item_segment, span)));
         }
@@ -617,7 +609,6 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         parent_args: &[ty::GenericArg<'tcx>],
         segment: &hir::PathSegment<'tcx>,
         self_ty: Option<Ty<'tcx>>,
-        pos: GenericArgPosition,
     ) -> (GenericArgsRef<'tcx>, GenericArgCountResult) {
         // If the type is parameterized by this region, then replace this
         // region with the current anon region binding (in other words,
@@ -640,8 +631,14 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             assert!(self_ty.is_none());
         }
 
-        let arg_count =
-            check_generic_arg_count(self, def_id, segment, generics, pos, self_ty.is_some());
+        let arg_count = check_generic_arg_count(
+            self,
+            def_id,
+            segment,
+            generics,
+            GenericArgPosition::Type,
+            self_ty.is_some(),
+        );
 
         // Skip processing if type has no generic parameters.
         // Traits always have `Self` as a generic parameter, which means they will not return early
@@ -826,14 +823,8 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         item_segment: &hir::PathSegment<'tcx>,
         parent_args: GenericArgsRef<'tcx>,
     ) -> GenericArgsRef<'tcx> {
-        let (args, _) = self.lower_generic_args_of_path(
-            span,
-            item_def_id,
-            parent_args,
-            item_segment,
-            None,
-            GenericArgPosition::Type,
-        );
+        let (args, _) =
+            self.lower_generic_args_of_path(span, item_def_id, parent_args, item_segment, None);
         if let Some(c) = item_segment.args().constraints.first() {
             prohibit_assoc_item_constraint(self, c, Some((item_def_id, item_segment, span)));
         }
@@ -945,7 +936,6 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             &[],
             segment,
             Some(self_ty),
-            GenericArgPosition::Type,
         );
 
         let constraints = segment.args().constraints;
@@ -1121,14 +1111,8 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
     ) -> ty::TraitRef<'tcx> {
         self.report_internal_fn_trait(span, trait_def_id, trait_segment, is_impl);
 
-        let (generic_args, _) = self.lower_generic_args_of_path(
-            span,
-            trait_def_id,
-            &[],
-            trait_segment,
-            Some(self_ty),
-            GenericArgPosition::Type,
-        );
+        let (generic_args, _) =
+            self.lower_generic_args_of_path(span, trait_def_id, &[], trait_segment, Some(self_ty));
         if let Some(c) = trait_segment.args().constraints.first() {
             prohibit_assoc_item_constraint(self, c, Some((trait_def_id, trait_segment, span)));
         }

compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs

@@ -13,7 +13,7 @@ use rustc_hir::lang_items::LangItem;
 use rustc_hir::{self as hir, AmbigArg, ExprKind, GenericArg, HirId, Node, QPath, intravisit};
 use rustc_hir_analysis::hir_ty_lowering::errors::GenericsArgsErrExtend;
 use rustc_hir_analysis::hir_ty_lowering::generics::{
-    check_generic_arg_count_for_call, lower_generic_args,
+    check_generic_arg_count_for_value_path, lower_generic_args,
 };
 use rustc_hir_analysis::hir_ty_lowering::{
     ExplicitLateBound, GenericArgCountMismatch, GenericArgCountResult, GenericArgsLowerer,
@@ -1098,8 +1098,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             // parameter internally, but we don't allow users to specify the
             // parameter's value explicitly, so we have to do some error-
             // checking here.
-            let arg_count =
-                check_generic_arg_count_for_call(self, def_id, generics, seg, IsMethodCall::No);
+            let arg_count = check_generic_arg_count_for_value_path(
+                self,
+                def_id,
+                generics,
+                seg,
+                IsMethodCall::No,
+            );
 
             if let ExplicitLateBound::Yes = arg_count.explicit_late_bound {
                 explicit_late_bound = ExplicitLateBound::Yes;

compiler/rustc_hir_typeck/src/method/confirm.rs

@@ -5,7 +5,7 @@ use rustc_hir as hir;
 use rustc_hir::GenericArg;
 use rustc_hir::def_id::DefId;
 use rustc_hir_analysis::hir_ty_lowering::generics::{
-    check_generic_arg_count_for_call, lower_generic_args,
+    check_generic_arg_count_for_value_path, lower_generic_args,
 };
 use rustc_hir_analysis::hir_ty_lowering::{
     GenericArgsLowerer, HirTyLowerer, IsMethodCall, RegionInferReason,
@@ -403,7 +403,7 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
         // variables.
         let generics = self.tcx.generics_of(pick.item.def_id);
 
-        let arg_count_correct = check_generic_arg_count_for_call(
+        let arg_count_correct = check_generic_arg_count_for_value_path(
             self.fcx,
             pick.item.def_id,
             generics,

tests/ui/delegation/generics/generics-gen-args-errors.rs

@@ -36,6 +36,7 @@ mod test_1 {
         //~| ERROR can't use generic parameters from outer item
         //~| ERROR can't use generic parameters from outer item
         //~| ERROR: unresolved item provided when a constant was expected
+        //~| ERROR: function takes 2 lifetime arguments but 0 lifetime arguments were supplied
     }
 }
 
@@ -47,6 +48,7 @@ mod test_2 {
 
     reuse foo::<String, String> as bar2;
     //~^ ERROR: function takes 3 generic arguments but 2 generic arguments were supplied
+    //~| ERROR: function takes 2 lifetime arguments but 0 lifetime arguments were supplied
 
     reuse foo::<'static, _, 'asdasd, 'static, 'static, 'static, _> as bar3;
     //~^ ERROR: use of undeclared lifetime name `'asdasd`
@@ -58,10 +60,12 @@ mod test_2 {
 
     reuse foo::<1, 2, _, 4, 5, _> as bar5;
     //~^ ERROR: function takes 3 generic arguments but 6 generic arguments were supplied
+    //~| ERROR: function takes 2 lifetime arguments but 0 lifetime arguments were supplied
 
     reuse foo::<1, 2,asd,String, { let x = 0; }> as bar6;
     //~^ ERROR: cannot find type `asd` in this scope
     //~| ERROR: function takes 3 generic arguments but 5 generic arguments were supplied
+    //~| ERROR: function takes 2 lifetime arguments but 0 lifetime arguments were supplied
 
     reuse foo::<"asdasd", asd, "askdn", 'static, 'a> as bar7;
     //~^ ERROR: use of undeclared lifetime name `'a`
@@ -70,6 +74,7 @@ mod test_2 {
 
     reuse foo::<{}, {}, {}> as bar8;
     //~^ ERROR: constant provided when a type was expected
+    //~| ERROR: function takes 2 lifetime arguments but 0 lifetime arguments were supplied
 }
 
 mod test_3 {
@@ -107,12 +112,14 @@ mod test_3 {
     //~| ERROR: trait takes 3 lifetime arguments but 1 lifetime argument was supplied
     //~| ERROR: trait takes 2 generic arguments but 3 generic arguments were supplied
     //~| ERROR: method takes 2 generic arguments but 6 generic arguments were supplied
+    //~| ERROR: method takes 1 lifetime argument but 0 lifetime arguments were supplied
 
     reuse Trait::<Trait, Clone, _, 'static, dyn Send, _>::foo::<1, 2, 3, _, 6> as bar7;
     //~^ ERROR: missing lifetime specifiers [E0106]
     //~| ERROR: trait takes 3 lifetime arguments but 1 lifetime argument was supplied
     //~| ERROR: trait takes 2 generic arguments but 5 generic arguments were supplied
     //~| ERROR: method takes 2 generic arguments but 5 generic arguments were supplied
+    //~| ERROR: method takes 1 lifetime argument but 0 lifetime arguments were supplied
 }
 
 fn main() {}