diff --git a/src/librustc_trans/trans/common.rs b/src/librustc_trans/trans/common.rs
index 88d9d42e840..0689b0ded6e 100644
--- a/src/librustc_trans/trans/common.rs
+++ b/src/librustc_trans/trans/common.rs
@@ -120,7 +120,16 @@ pub fn erase_regions<'tcx,T>(cx: &ty::ctxt<'tcx>, value: &T) -> T
 // Is the type's representation size known at compile time?
 pub fn type_is_sized<'tcx>(tcx: &ty::ctxt<'tcx>, ty: Ty<'tcx>) -> bool {
     let param_env = ty::empty_parameter_environment(tcx);
-    ty::type_is_sized(&param_env, DUMMY_SP, ty)
+    // FIXME(#4287) This can cause errors due to polymorphic recursion,
+    // a better span should be provided, if available.
+    let err_count = tcx.sess.err_count();
+    let is_sized = ty::type_is_sized(&param_env, DUMMY_SP, ty);
+    // Those errors aren't fatal, but an incorrect result can later
+    // trip over asserts in both rustc's trans and LLVM.
+    if err_count < tcx.sess.err_count() {
+        tcx.sess.abort_if_errors();
+    }
+    is_sized
 }
 
 pub fn type_is_fat_ptr<'tcx>(cx: &ty::ctxt<'tcx>, ty: Ty<'tcx>) -> bool {
diff --git a/src/test/compile-fail/infinite-instantiation.rs b/src/test/compile-fail/infinite-instantiation.rs
index 2642ac6204c..d39efa3c2ab 100644
--- a/src/test/compile-fail/infinite-instantiation.rs
+++ b/src/test/compile-fail/infinite-instantiation.rs
@@ -1,4 +1,4 @@
-// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //
@@ -8,28 +8,34 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// error-pattern: reached the recursion limit during monomorphization
-// issue 2258
+//~^^^^^^^^^^ ERROR overflow
+//
+// We get an error message at the top of file (dummy span).
+// This is not helpful, but also kind of annoying to prevent,
+// so for now just live with it.
+// This test case was originally for issue #2258.
 
-trait to_opt {
+trait ToOpt {
     fn to_option(&self) -> Option<Self>;
 }
 
-impl to_opt for usize {
+impl ToOpt for usize {
     fn to_option(&self) -> Option<usize> {
         Some(*self)
     }
 }
 
-impl<T:Clone> to_opt for Option<T> {
+impl<T:Clone> ToOpt for Option<T> {
     fn to_option(&self) -> Option<Option<T>> {
         Some((*self).clone())
     }
 }
 
-fn function<T:to_opt + Clone>(counter: usize, t: T) {
+fn function<T:ToOpt + Clone>(counter: usize, t: T) {
     if counter > 0_usize {
         function(counter - 1_usize, t.to_option());
+        // FIXME(#4287) Error message should be here. It should be
+        // a type error to instantiate `test` at a type other than T.
     }
 }
 
diff --git a/src/test/compile-fail/recursion.rs b/src/test/compile-fail/recursion.rs
index ffc21a5ce61..55f3b995336 100644
--- a/src/test/compile-fail/recursion.rs
+++ b/src/test/compile-fail/recursion.rs
@@ -1,4 +1,4 @@
-// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //
@@ -10,10 +10,9 @@
 
 //~^^^^^^^^^^ ERROR overflow
 //
-// We also get a second error message at the top of file (dummy
-// span). This is not helpful, but also kind of annoying to prevent,
-// so for now just live with it, since we also get a second message
-// that is more helpful.
+// We get an error message at the top of file (dummy span).
+// This is not helpful, but also kind of annoying to prevent,
+// so for now just live with it.
 
 enum Nil {NilValue}
 struct Cons<T> {head:isize, tail:T}
@@ -28,9 +27,8 @@ impl<T:Dot> Dot for Cons<T> {
 }
 fn test<T:Dot> (n:isize, i:isize, first:T, second:T) ->isize {
   match n {    0 => {first.dot(second)}
-      //~^ ERROR: reached the recursion limit during monomorphization
-      // Error message should be here. It should be a type error
-      // to instantiate `test` at a type other than T. (See #4287)
+      // FIXME(#4287) Error message should be here. It should be
+      // a type error to instantiate `test` at a type other than T.
     _ => {test (n-1, i+1, Cons {head:2*i+1, tail:first}, Cons{head:i*i, tail:second})}
   }
 }