Improve spans of non-WF implied bound types

4 files changed, 82 insertions, 51 deletions

diff --git a/compiler/rustc_hir_analysis/src/check/wfcheck.rs b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
index 1afe6242403..b663f90cab7 100644
--- a/compiler/rustc_hir_analysis/src/check/wfcheck.rs
+++ b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
@@ -1489,54 +1489,38 @@ fn check_fn_or_method<'tcx>(
     def_id: LocalDefId,
 ) {
     let tcx = wfcx.tcx();
-    let sig = tcx.liberate_late_bound_regions(def_id.to_def_id(), sig);
+    let mut sig = tcx.liberate_late_bound_regions(def_id.to_def_id(), sig);
 
     // Normalize the input and output types one at a time, using a different
     // `WellFormedLoc` for each. We cannot call `normalize_associated_types`
     // on the entire `FnSig`, since this would use the same `WellFormedLoc`
     // for each type, preventing the HIR wf check from generating
     // a nice error message.
-    let ty::FnSig { mut inputs_and_output, c_variadic, unsafety, abi } = sig;
-    inputs_and_output = tcx.mk_type_list(inputs_and_output.iter().enumerate().map(|(i, ty)| {
-        wfcx.normalize(
-            span,
-            Some(WellFormedLoc::Param {
-                function: def_id,
-                // Note that the `param_idx` of the output type is
-                // one greater than the index of the last input type.
-                param_idx: i.try_into().unwrap(),
-            }),
-            ty,
-        )
-    }));
-    // Manually call `normalize_associated_types_in` on the other types
-    // in `FnSig`. This ensures that if the types of these fields
-    // ever change to include projections, we will start normalizing
-    // them automatically.
-    let sig = ty::FnSig {
-        inputs_and_output,
-        c_variadic: wfcx.normalize(span, None, c_variadic),
-        unsafety: wfcx.normalize(span, None, unsafety),
-        abi: wfcx.normalize(span, None, abi),
-    };
+    let arg_span =
+        |idx| hir_decl.inputs.get(idx).map_or(hir_decl.output.span(), |arg: &hir::Ty<'_>| arg.span);
+
+    sig.inputs_and_output =
+        tcx.mk_type_list(sig.inputs_and_output.iter().enumerate().map(|(idx, ty)| {
+            wfcx.normalize(
+                arg_span(idx),
+                Some(WellFormedLoc::Param {
+                    function: def_id,
+                    // Note that the `param_idx` of the output type is
+                    // one greater than the index of the last input type.
+                    param_idx: idx.try_into().unwrap(),
+                }),
+                ty,
+            )
+        }));
 
-    for (i, (&input_ty, ty)) in iter::zip(sig.inputs(), hir_decl.inputs).enumerate() {
+    for (idx, ty) in sig.inputs_and_output.iter().enumerate() {
         wfcx.register_wf_obligation(
-            ty.span,
-            Some(WellFormedLoc::Param { function: def_id, param_idx: i.try_into().unwrap() }),
-            input_ty.into(),
+            arg_span(idx),
+            Some(WellFormedLoc::Param { function: def_id, param_idx: idx.try_into().unwrap() }),
+            ty.into(),
         );
     }
 
-    wfcx.register_wf_obligation(
-        hir_decl.output.span(),
-        Some(WellFormedLoc::Param {
-            function: def_id,
-            param_idx: sig.inputs().len().try_into().unwrap(),
-        }),
-        sig.output().into(),
-    );
-
     check_where_clauses(wfcx, span, def_id);
 
     check_return_position_impl_trait_in_trait_bounds(
diff --git a/compiler/rustc_middle/src/query/mod.rs b/compiler/rustc_middle/src/query/mod.rs
index 37db2274f67..7f794a926c0 100644
--- a/compiler/rustc_middle/src/query/mod.rs
+++ b/compiler/rustc_middle/src/query/mod.rs
@@ -803,7 +803,7 @@ rustc_queries! {
     ///
     /// Note that we've liberated the late bound regions of function signatures, so
     /// this can not be used to check whether these types are well formed.
-    query assumed_wf_types(key: DefId) -> &'tcx ty::List<Ty<'tcx>> {
+    query assumed_wf_types(key: DefId) -> &'tcx [(Ty<'tcx>, Span)] {
         desc { |tcx| "computing the implied bounds of `{}`", tcx.def_path_str(key) }
     }
 
diff --git a/compiler/rustc_trait_selection/src/traits/engine.rs b/compiler/rustc_trait_selection/src/traits/engine.rs
index bc6d9d4b922..72ed3aa499d 100644
--- a/compiler/rustc_trait_selection/src/traits/engine.rs
+++ b/compiler/rustc_trait_selection/src/traits/engine.rs
@@ -191,8 +191,8 @@ impl<'a, 'tcx> ObligationCtxt<'a, 'tcx> {
         let assumed_wf_types = tcx.assumed_wf_types(def_id);
         let mut implied_bounds = FxIndexSet::default();
         let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
-        let cause = ObligationCause::misc(span, hir_id);
-        for ty in assumed_wf_types {
+        for &(ty, ty_span) in assumed_wf_types {
+            let span = if ty_span.is_dummy() { span } else { ty_span };
             // FIXME(@lcnr): rustc currently does not check wf for types
             // pre-normalization, meaning that implied bounds are sometimes
             // incorrect. See #100910 for more details.
@@ -205,7 +205,7 @@ impl<'a, 'tcx> ObligationCtxt<'a, 'tcx> {
             // sound and then uncomment this line again.
 
             // implied_bounds.insert(ty);
-            let normalized = self.normalize(&cause, param_env, ty);
+            let normalized = self.normalize(&ObligationCause::misc(span, hir_id), param_env, ty);
             implied_bounds.insert(normalized);
         }
         implied_bounds
diff --git a/compiler/rustc_ty_utils/src/implied_bounds.rs b/compiler/rustc_ty_utils/src/implied_bounds.rs
index b7a24a22c53..e3f34373ccc 100644
--- a/compiler/rustc_ty_utils/src/implied_bounds.rs
+++ b/compiler/rustc_ty_utils/src/implied_bounds.rs
@@ -1,33 +1,80 @@
 use crate::rustc_middle::ty::DefIdTree;
-use rustc_hir::{def::DefKind, def_id::DefId};
+use rustc_hir::{self as hir, def::DefKind, def_id::DefId};
 use rustc_middle::ty::{self, Ty, TyCtxt};
+use rustc_span::{Span, DUMMY_SP};
 
 pub fn provide(providers: &mut ty::query::Providers) {
     *providers = ty::query::Providers { assumed_wf_types, ..*providers };
 }
 
-fn assumed_wf_types(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::List<Ty<'_>> {
+fn assumed_wf_types(tcx: TyCtxt<'_>, def_id: DefId) -> &[(Ty<'_>, Span)] {
     match tcx.def_kind(def_id) {
         DefKind::Fn => {
             let sig = tcx.fn_sig(def_id);
             let liberated_sig = tcx.liberate_late_bound_regions(def_id, sig);
-            liberated_sig.inputs_and_output
+            if let Some(node) = tcx.hir().get_if_local(def_id)
+                && let Some(decl) = node.fn_decl()
+            {
+                assert_eq!(decl.inputs.len(), liberated_sig.inputs().len());
+                tcx.arena.alloc_from_iter(std::iter::zip(
+                    liberated_sig.inputs_and_output,
+                    decl.inputs.iter().map(|ty| ty.span).chain([decl.output.span()]),
+                ))
+            } else {
+                tcx.arena.alloc_from_iter(
+                    liberated_sig.inputs_and_output.iter().map(|ty| (ty, DUMMY_SP)),
+                )
+            }
         }
         DefKind::AssocFn => {
             let sig = tcx.fn_sig(def_id);
             let liberated_sig = tcx.liberate_late_bound_regions(def_id, sig);
-            let mut assumed_wf_types: Vec<_> =
-                tcx.assumed_wf_types(tcx.parent(def_id)).as_slice().into();
-            assumed_wf_types.extend(liberated_sig.inputs_and_output);
-            tcx.intern_type_list(&assumed_wf_types)
+            let assumed_wf_types = tcx.assumed_wf_types(tcx.parent(def_id));
+            if let Some(node) = tcx.hir().get_if_local(def_id)
+                && let Some(decl) = node.fn_decl()
+            {
+                assert_eq!(decl.inputs.len(), liberated_sig.inputs().len());
+                tcx.arena.alloc_from_iter(assumed_wf_types.iter().copied().chain(std::iter::zip(
+                    liberated_sig.inputs_and_output,
+                    decl.inputs.iter().map(|ty| ty.span).chain([decl.output.span()]),
+                )))
+            } else {
+                tcx.arena.alloc_from_iter(assumed_wf_types.iter().copied().chain(
+                    liberated_sig.inputs_and_output.iter().map(|ty| (ty, DUMMY_SP)),
+                ))
+            }
         }
         DefKind::Impl => match tcx.impl_trait_ref(def_id) {
             Some(trait_ref) => {
                 let types: Vec<_> = trait_ref.substs.types().collect();
-                tcx.intern_type_list(&types)
+                let self_span = if let Some(hir::Node::Item(hir::Item {
+                    kind: hir::ItemKind::Impl(impl_),
+                    ..
+                })) = tcx.hir().get_if_local(def_id)
+                {
+                    impl_.self_ty.span
+                } else {
+                    DUMMY_SP
+                };
+                tcx.arena.alloc_from_iter(std::iter::zip(
+                    types,
+                    // FIXME: reliable way of getting trait ref substs...
+                    [self_span].into_iter().chain(std::iter::repeat(DUMMY_SP)),
+                ))
             }
             // Only the impl self type
-            None => tcx.intern_type_list(&[tcx.type_of(def_id)]),
+            None => {
+                let span = if let Some(hir::Node::Item(hir::Item {
+                    kind: hir::ItemKind::Impl(impl_),
+                    ..
+                })) = tcx.hir().get_if_local(def_id)
+                {
+                    impl_.self_ty.span
+                } else {
+                    DUMMY_SP
+                };
+                tcx.arena.alloc_from_iter([(tcx.type_of(def_id), span)])
+            }
         },
         DefKind::AssocConst | DefKind::AssocTy => tcx.assumed_wf_types(tcx.parent(def_id)),
         DefKind::Mod
@@ -56,6 +103,6 @@ fn assumed_wf_types(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::List<Ty<'_>> {
         | DefKind::LifetimeParam
         | DefKind::GlobalAsm
         | DefKind::Closure
-        | DefKind::Generator => ty::List::empty(),
+        | DefKind::Generator => &[],
     }
 }