Auto merge of #42969 - arielb1:struct-err, r=eddyb

mem_categorization: handle type-based paths in variant patterns

These can't be used in correct programs, but must be handled in order to
prevent ICEs.

Fixes #42880.

r? @eddyb

src/test/compile-fail/issue-42880.rs

@@ -0,0 +1,18 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+type Value = String;
+
+fn main() {
+    let f = |&Value::String(_)| (); //~ ERROR no associated item named
+
+    let vec: Vec<Value> = Vec::new();
+    vec.last().map(f);
+}