Auto merge of rust-lang#11258 - Jarcho:ice_11256, r=Centri3

Resolve type aliases in `type_certainty`

Fixes rust-lang#11256

changelog: `unwrap_or_default`: Fix ICE when local types are declared using alias types

Author: bors

clippy_utils/src/ty/type_certainty/mod.rs

@@ -12,7 +12,7 @@
 //! be considered a bug.
 
 use crate::def_path_res;
-use rustc_hir::def::Res;
+use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::DefId;
 use rustc_hir::intravisit::{walk_qpath, walk_ty, Visitor};
 use rustc_hir::{self as hir, Expr, ExprKind, GenericArgs, HirId, Node, PathSegment, QPath, TyKind};
@@ -219,7 +219,12 @@ fn path_segment_certainty(
                 // See the comment preceding `qpath_certainty`. `def_id` could refer to a type or a value.
                 let certainty = lhs.join_clearing_def_ids(rhs);
                 if resolves_to_type {
-                    certainty.with_def_id(def_id)
+                    if cx.tcx.def_kind(def_id) == DefKind::TyAlias {
+                        adt_def_id(cx.tcx.type_of(def_id).instantiate_identity())
+                            .map_or(certainty, |def_id| certainty.with_def_id(def_id))
+                    } else {
+                        certainty.with_def_id(def_id)
+                    }
                 } else {
                     certainty
                 }

tests/ui/unwrap_or_else_default.fixed

@@ -109,6 +109,10 @@ fn type_certainty(option: Option<Vec<u64>>) {
     // should not be changed: no type annotation, unconcretized initializer
     let option = None;
     option.unwrap_or_else(Vec::new).push(1);
+
+    type Alias = Option<Vec<u32>>;
+    let option: Alias = Option::<Vec<u32>>::Some(Vec::new());
+    option.unwrap_or_default().push(1);
 }
 
 fn method_call_with_deref() {

tests/ui/unwrap_or_else_default.rs

@@ -109,6 +109,10 @@ fn type_certainty(option: Option<Vec<u64>>) {
     // should not be changed: no type annotation, unconcretized initializer
     let option = None;
     option.unwrap_or_else(Vec::new).push(1);
+
+    type Alias = Option<Vec<u32>>;
+    let option: Alias = Option::<Vec<u32>>::Some(Vec::new());
+    option.unwrap_or_else(Vec::new).push(1);
 }
 
 fn method_call_with_deref() {

tests/ui/unwrap_or_else_default.stderr

@@ -84,11 +84,17 @@ error: use of `unwrap_or_else` to construct default value
 LL |     option.unwrap_or_else(Vec::new).push(1);
    |            ^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `unwrap_or_default()`
 
+error: use of `unwrap_or_else` to construct default value
+  --> $DIR/unwrap_or_else_default.rs:115:12
+   |
+LL |     option.unwrap_or_else(Vec::new).push(1);
+   |            ^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `unwrap_or_default()`
+
 error: use of `or_insert_with` to construct default value
-  --> $DIR/unwrap_or_else_default.rs:128:32
+  --> $DIR/unwrap_or_else_default.rs:132:32
    |
 LL |     let _ = inner_map.entry(0).or_insert_with(Default::default);
    |                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `or_default()`
 
-error: aborting due to 15 previous errors
+error: aborting due to 16 previous errors