Auto merge of #34336 - petrochenkov:icemctuple, r=arielb1

Fix ICE in memory categorization of tuple patterns

Fixes https://github.com/rust-lang/rust/issues/34334

It seems to be ok for `pat_ty` to return `Err` even if type checking is done, because it uses `infcx.node_ty` which is supposed to return `Err` for all kinds of erroneous types so its callers could quickly bail out with `?`.

r? @arielb1

src/librustc/middle/mem_categorization.rs

@@ -1145,8 +1145,8 @@ fn cat_pattern_<F>(&self, cmt: cmt<'tcx>, pat: &hir::Pat, op: &mut F)
                     }
                 }
                 Some(Def::Struct(..)) => {
-                    let expected_len = match self.pat_ty(&pat) {
-                        Ok(&ty::TyS{sty: ty::TyStruct(adt_def, _), ..}) => {
+                    let expected_len = match self.pat_ty(&pat)?.sty {
+                        ty::TyStruct(adt_def, _) => {
                             adt_def.struct_variant().fields.len()
                         }
                         ref ty => {
@@ -1196,8 +1196,8 @@ fn cat_pattern_<F>(&self, cmt: cmt<'tcx>, pat: &hir::Pat, op: &mut F)
 
           PatKind::Tuple(ref subpats, ddpos) => {
             // (p1, ..., pN)
-            let expected_len = match self.pat_ty(&pat) {
-                Ok(&ty::TyS{sty: ty::TyTuple(ref tys), ..}) => tys.len(),
+            let expected_len = match self.pat_ty(&pat)?.sty {
+                ty::TyTuple(ref tys) => tys.len(),
                 ref ty => span_bug!(pat.span, "tuple pattern unexpected type {:?}", ty),
             };
             for (i, subpat) in subpats.iter().enumerate_and_adjust(expected_len, ddpos) {

src/test/compile-fail/issue-34334.rs

+// Copyright 2016 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.
+
+fn main () {
+    let sr: Vec<(u32, _, _) = vec![]; //~ ERROR expected one of `+`, `,`, or `>`, found `=`
+    let sr2: Vec<(u32, _, _)> = sr.iter().map(|(faction, th_sender, th_receiver)| {}).collect();
+    //~^ ERROR unresolved name `sr`
+}