From 6bb1e2291195a518ddeef6e64337f4edb1432a72 Mon Sep 17 00:00:00 2001
From: Niko Matsakis <niko@alum.mit.edu>
Date: Fri, 7 Aug 2015 09:43:40 -0400
Subject: [PATCH] New WF condition requires checking that argument types are WF
 on every call. This ensures that implies bounds are reasonable (the older
 code only checked that the values provided had WF types, but we also must
 know that the formal types of the arguments are WF.)

---
 src/librustc_typeck/check/mod.rs | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/src/librustc_typeck/check/mod.rs b/src/librustc_typeck/check/mod.rs
index df8a80792a34..bf5d1373d0bf 100644
--- a/src/librustc_typeck/check/mod.rs
+++ b/src/librustc_typeck/check/mod.rs
@@ -2432,6 +2432,12 @@ fn check_argument_types<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>,
         1
     };
 
+    // All the input types from the fn signature must outlive the call
+    // so as to validate implied bounds.
+    for &fn_input_ty in fn_inputs {
+        fcx.register_wf_obligation(fn_input_ty, sp, traits::MiscObligation);
+    }
+
     let mut expected_arg_tys = expected_arg_tys;
     let expected_arg_count = fn_inputs.len();
     let formal_tys = if tuple_arguments == TupleArguments {
@@ -3541,16 +3547,18 @@ fn check_expr_with_unifier<'a, 'tcx, F>(fcx: &FnCtxt<'a, 'tcx>,
       }
       ast::ExprCall(ref callee, ref args) => {
           callee::check_call(fcx, expr, &**callee, &args[..], expected);
+
+          // we must check that return type of called functions is WF:
+          let ret_ty = fcx.expr_ty(expr);
+          fcx.register_wf_obligation(ret_ty, expr.span, traits::MiscObligation);
       }
       ast::ExprMethodCall(ident, ref tps, ref args) => {
-        check_method_call(fcx, expr, ident, &args[..], &tps[..], expected, lvalue_pref);
-        let arg_tys = args.iter().map(|a| fcx.expr_ty(&**a));
-        let  args_err = arg_tys.fold(false,
-             |rest_err, a| {
-              rest_err || a.references_error()});
-        if args_err {
-            fcx.write_error(id);
-        }
+          check_method_call(fcx, expr, ident, &args[..], &tps[..], expected, lvalue_pref);
+          let arg_tys = args.iter().map(|a| fcx.expr_ty(&**a));
+          let args_err = arg_tys.fold(false, |rest_err, a| rest_err || a.references_error());
+          if args_err {
+              fcx.write_error(id);
+          }
       }
       ast::ExprCast(ref e, ref t) => {
         if let ast::TyFixedLengthVec(_, ref count_expr) = t.node {