rustc: Don't generate code for unreachable expressions

The way we deal with unreachable expressions in trans is pretty ad hoc,
but this at least doesn't make it worse, and eliminates the LLVM
assertion failure reported in #5741.

2 files changed, 18 insertions, 0 deletions

diff --git a/src/librustc/middle/trans/expr.rs b/src/librustc/middle/trans/expr.rs
index f457cc80da8..9349c2bcd26 100644
--- a/src/librustc/middle/trans/expr.rs
+++ b/src/librustc/middle/trans/expr.rs
@@ -499,6 +499,10 @@ fn trans_rvalue_stmt_unadjusted(bcx: block, expr: @ast::expr) -> block {
     let mut bcx = bcx;
     let _icx = bcx.insn_ctxt("trans_rvalue_stmt");
 
+    if bcx.unreachable {
+        return bcx;
+    }
+
     trace_span!(bcx, expr.span, @shorten(bcx.expr_to_str(expr)));
 
     match expr.node {
diff --git a/src/test/run-pass/issue-5741.rs b/src/test/run-pass/issue-5741.rs
new file mode 100644
index 00000000000..b80e37a425b
--- /dev/null
+++ b/src/test/run-pass/issue-5741.rs
@@ -0,0 +1,14 @@
+// Copyright 2013 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() {
+    return;
+    while io::stdin().read_line() != ~"quit" { };
+}