From b69090102e409fd8139ab554fcd38e567fda470f Mon Sep 17 00:00:00 2001
From: Alik Aslanyan <inline0@protonmail.com>
Date: Thu, 15 Jul 2021 16:34:45 +0400
Subject: [PATCH] Suggest full enum variant for local modules

---
 compiler/rustc_typeck/src/check/demand.rs        |  4 +++-
 ...suggest-full-enum-variant-for-local-module.rs | 10 ++++++++++
 ...est-full-enum-variant-for-local-module.stderr | 16 ++++++++++++++++
 3 files changed, 29 insertions(+), 1 deletion(-)
 create mode 100644 src/test/ui/suggestions/suggest-full-enum-variant-for-local-module.rs
 create mode 100644 src/test/ui/suggestions/suggest-full-enum-variant-for-local-module.stderr

diff --git a/compiler/rustc_typeck/src/check/demand.rs b/compiler/rustc_typeck/src/check/demand.rs
index 33bc25accb319..3ea59906d3dcd 100644
--- a/compiler/rustc_typeck/src/check/demand.rs
+++ b/compiler/rustc_typeck/src/check/demand.rs
@@ -10,6 +10,7 @@ use rustc_hir::lang_items::LangItem;
 use rustc_hir::{is_range_literal, Node};
 use rustc_middle::lint::in_external_macro;
 use rustc_middle::ty::adjustment::AllowTwoPhase;
+use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_middle::ty::{self, AssocItem, Ty, TypeAndMut};
 use rustc_span::symbol::sym;
 use rustc_span::Span;
@@ -201,7 +202,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     let sole_field = &variant.fields[0];
                     let sole_field_ty = sole_field.ty(self.tcx, substs);
                     if self.can_coerce(expr_ty, sole_field_ty) {
-                        let variant_path = self.tcx.def_path_str(variant.def_id);
+                        let variant_path =
+                            with_no_trimmed_paths(|| self.tcx.def_path_str(variant.def_id));
                         // FIXME #56861: DRYer prelude filtering
                         if let Some(path) = variant_path.strip_prefix("std::prelude::") {
                             if let Some((_, path)) = path.split_once("::") {
diff --git a/src/test/ui/suggestions/suggest-full-enum-variant-for-local-module.rs b/src/test/ui/suggestions/suggest-full-enum-variant-for-local-module.rs
new file mode 100644
index 0000000000000..1dfc0786668f2
--- /dev/null
+++ b/src/test/ui/suggestions/suggest-full-enum-variant-for-local-module.rs
@@ -0,0 +1,10 @@
+mod option {
+    pub enum O<T> {
+        Some(T),
+        None,
+    }
+}
+
+fn main() {
+    let _: option::O<()> = (); //~ ERROR 9:28: 9:30: mismatched types [E0308]
+}
diff --git a/src/test/ui/suggestions/suggest-full-enum-variant-for-local-module.stderr b/src/test/ui/suggestions/suggest-full-enum-variant-for-local-module.stderr
new file mode 100644
index 0000000000000..22a0ce1e91d72
--- /dev/null
+++ b/src/test/ui/suggestions/suggest-full-enum-variant-for-local-module.stderr
@@ -0,0 +1,16 @@
+error[E0308]: mismatched types
+  --> $DIR/suggest-full-enum-variant-for-local-module.rs:9:28
+   |
+LL |     let _: option::O<()> = ();
+   |            -------------   ^^
+   |            |               |
+   |            |               expected enum `O`, found `()`
+   |            |               help: try using a variant of the expected enum: `option::O::Some(())`
+   |            expected due to this
+   |
+   = note:   expected enum `O<()>`
+           found unit type `()`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0308`.