Fix error spans for arguments to tuple enum constructors

1 files changed, 13 insertions, 6 deletions

diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/adjust_fulfillment_errors.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/adjust_fulfillment_errors.rs
index 3b72326be7c..778e0bdaefd 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/adjust_fulfillment_errors.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/adjust_fulfillment_errors.rs
@@ -714,12 +714,19 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     self.tcx.parent(expr_ctor_def_id)
                 }
                 hir::def::DefKind::Ctor(hir::def::CtorOf::Variant, hir::def::CtorKind::Fn) => {
-                    if in_ty_adt.did() == self.tcx.parent(expr_ctor_def_id) {
-                        // The constructor definition refers to the variant:
-                        // For example, for a local type `MyEnum::MyVariant` triggers this case.
-                        expr_ctor_def_id
-                    } else if in_ty_adt.did() == self.tcx.parent(self.tcx.parent(expr_ctor_def_id))
-                    {
+                    // For a typical enum like
+                    // `enum Blah<T> { Variant(T) }`
+                    // we get the following resolutions:
+                    // - expr_ctor_def_id :::                                   DefId(0:29 ~ source_file[b442]::Blah::Variant::{constructor#0})
+                    // - self.tcx.parent(expr_ctor_def_id) :::                  DefId(0:28 ~ source_file[b442]::Blah::Variant)
+                    // - self.tcx.parent(self.tcx.parent(expr_ctor_def_id)) ::: DefId(0:26 ~ source_file[b442]::Blah)
+
+                    // Therefore, we need to go up once to obtain the variant and up twice to obtain the type.
+                    // Note that this pattern still holds even when we `use` a variant or `use` an enum type to rename it, or chain `use` expressions
+                    // together; this resolution is handled automatically by `qpath_res`.
+
+                    // FIXME: Deal with type aliases?
+                    if in_ty_adt.did() == self.tcx.parent(self.tcx.parent(expr_ctor_def_id)) {
                         // The constructor definition refers to the "constructor" of the variant:
                         // For example, `Some(5)` triggers this case.
                         self.tcx.parent(expr_ctor_def_id)