Catch returns from within when blocks and provide an error message (#842)

Resolves #841

1 files changed, 22 insertions, 0 deletions

diff --git a/src/test/scala/chiselTests/When.scala b/src/test/scala/chiselTests/When.scala
index a1a7afb7..58d5a1bd 100644
--- a/src/test/scala/chiselTests/When.scala
+++ b/src/test/scala/chiselTests/When.scala
@@ -106,4 +106,26 @@ class WhenSpec extends ChiselFlatSpec {
   "Conditional connections to submodule ports" should "be handled properly" in {
     assertTesterPasses(new SubmoduleWhenTester)
   }
+
+  "Returning in a when scope" should "give a reasonable error message" in {
+    val e = the [ChiselException] thrownBy {
+      elaborate(new Module {
+        val io = IO(new Bundle {
+          val foo = Input(UInt(8.W))
+          val bar = Input(UInt(8.W))
+          val cond = Input(Bool())
+          val out = Output(UInt(8.W))
+        })
+        def func(): UInt = {
+          when(io.cond) {
+            // This is bad, do not do this!!!
+            return io.foo
+          }
+          return io.bar
+        }
+        io.out := func()
+      })
+    }
+    e.getMessage should include ("Cannot exit from a when() block with a \"return\"")
+  }
 }