auto merge of #20167 : michaelwoerister/rust/for-loop-var, r=alexcrichton

... really this time `:)`

I went for the simpler fix after all since it turned out to become a bit too complicated to extract the current iteration value from its containing `Option` with the different memory layouts it can have. It's also what we already do for match bindings.

I also extended the new test case to include the "simple identifier" case.

Fixes #20127, fixes #19732

Author: bors

src/librustc_trans/trans/_match.rs

@@ -1554,7 +1554,8 @@ pub fn store_for_loop_binding<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
                                           -> Block<'blk, 'tcx> {
     let _icx = push_ctxt("match::store_for_loop_binding");
 
-    if simple_identifier(&*pat).is_some() {
+    if simple_identifier(&*pat).is_some() &&
+       bcx.sess().opts.debuginfo != FullDebugInfo {
         // Generate nicer LLVM for the common case of a `for` loop pattern
         // like `for x in blahblah { ... }`.
         let binding_type = node_id_type(bcx, pat.id);

src/librustc_trans/trans/controlflow.rs

@@ -286,6 +286,7 @@ pub fn trans_for<'blk, 'tcx>(mut bcx: Block<'blk, 'tcx>,
     debug!("iterator type is {}, datum type is {}",
            ppaux::ty_to_string(bcx.tcx(), iterator_type),
            ppaux::ty_to_string(bcx.tcx(), iterator_datum.ty));
+
     let lliterator = load_ty(bcx, iterator_datum.val, iterator_datum.ty);
 
     // Create our basic blocks and set up our loop cleanups.
@@ -365,6 +366,8 @@ pub fn trans_for<'blk, 'tcx>(mut bcx: Block<'blk, 'tcx>,
                                        llpayload,
                                        binding_cleanup_scope_id);
 
+    debuginfo::create_for_loop_var_metadata(body_bcx_in, pat);
+
     // Codegen the body.
     body_bcx_out = trans_block(body_bcx_out, body, expr::Ignore);
     body_bcx_out =