Add ability to suppress enum cast warnings (#2671) (#2674)

(cherry picked from commit 1ad820f7f549eddcd7188b737f59a240e48a7f0a)

Co-authored-by: Zachary Yedidia <zyedidia@gmail.com>

1 files changed, 25 insertions, 0 deletions

diff --git a/docs/src/explanations/chisel-enum.md b/docs/src/explanations/chisel-enum.md
index a390aea4..16b5570d 100644
--- a/docs/src/explanations/chisel-enum.md
+++ b/docs/src/explanations/chisel-enum.md
@@ -17,6 +17,7 @@ import chisel3._
 import chisel3.util._
 import chisel3.stage.ChiselStage
 import chisel3.experimental.ChiselEnum
+import chisel3.experimental.suppressEnumCastWarning
 ```
 
 ```scala mdoc:invisible
@@ -167,6 +168,30 @@ val (log2, _) = grabLog(ChiselStage.emitChirrtl(new SafeFromUInt))
 println(s"```\n$log2```")
 ```
 
+You can also suppress the warning by using `suppressEnumCastWarning`. This is
+primarily used for casting from [[UInt]] to a Bundle type that contains an
+Enum, where the [[UInt]] is known to be valid for the Bundle type.
+
+```scala mdoc
+class MyBundle extends Bundle {
+  val addr = UInt(8.W)
+  val op = Opcode()
+}
+
+class SuppressedFromUInt extends Module {
+  val in = IO(Input(UInt(15.W)))
+  val out = IO(Output(new MyBundle()))
+  suppressEnumCastWarning {
+    out := in.asTypeOf(new MyBundle)
+  }
+}
+```
+
+```scala mdoc:invisible
+val (log3, _) = grabLog(ChiselStage.emitChirrtl(new SuppressedFromUInt))
+assert(log3.isEmpty)
+```
+
 ## Testing
 
 The _Type_ of the enums values is `<ChiselEnum Object>.Type` which can be useful for passing the values