From d95cb262aefc06458652b227980a3cdc5471d3ba Mon Sep 17 00:00:00 2001
From: Jack Koenig
Date: Tue, 19 Dec 2017 17:33:07 -0800
Subject: Add WireInit.apply that accepts DontCare (#731)

Prevents DontCare from affecting type inference
Fixes #728
---
 .../src/main/scala/chisel3/core/Data.scala           |  9 ++++++++-
 src/main/scala/chisel3/package.scala                 |  4 ++++
 src/test/scala/chiselTests/WireSpec.scala            | 20 ++++++++++++++++++++
 3 files changed, 32 insertions(+), 1 deletion(-)
 create mode 100644 src/test/scala/chiselTests/WireSpec.scala

diff --git a/chiselFrontend/src/main/scala/chisel3/core/Data.scala b/chiselFrontend/src/main/scala/chisel3/core/Data.scala
index db99d6b3..19adf01b 100644
--- a/chiselFrontend/src/main/scala/chisel3/core/Data.scala
+++ b/chiselFrontend/src/main/scala/chisel3/core/Data.scala
@@ -451,13 +451,20 @@ object WireInit {
     apply(model, init)
   }
 
-  def apply[T <: Data](t: T, init: T)(implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): T = {
+  private def applyImpl[T <: Data](t: T, init: Data)(implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): T = {
     implicit val noSourceInfo = UnlocatableSourceInfo
     val x = Wire(t)
     requireIsHardware(init, "wire initializer")
     x := init
     x
   }
+
+  def apply[T <: Data](t: T, init: T)(implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): T = {
+    applyImpl(t, init)
+  }
+  def apply[T <: Data](t: T, init: DontCare.type)(implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): T = {
+    applyImpl(t, init)
+  }
 }
 
 /** RHS (source) for Invalidate API.
diff --git a/src/main/scala/chisel3/package.scala b/src/main/scala/chisel3/package.scala
index f31b4015..a502ef2d 100644
--- a/src/main/scala/chisel3/package.scala
+++ b/src/main/scala/chisel3/package.scala
@@ -32,6 +32,10 @@ package object chisel3 {    // scalastyle:ignore package.object.name
     @deprecated("Wire(t, init) is deprecated, use WireInit(t, init) instead", "chisel3")
     def apply[T <: Data](t: T, init: T)(implicit compileOptions: CompileOptions): T =
       chisel3.core.WireInit(t, init)
+
+    @deprecated("Wire(t, init) is deprecated, use WireInit(t, init) instead", "chisel3")
+    def apply[T <: Data](t: T, init: DontCare.type)(implicit compileOptions: CompileOptions): T =
+      chisel3.core.WireInit(t, init)
   }
   val WireInit = chisel3.core.WireInit
 
diff --git a/src/test/scala/chiselTests/WireSpec.scala b/src/test/scala/chiselTests/WireSpec.scala
new file mode 100644
index 00000000..051880ee
--- /dev/null
+++ b/src/test/scala/chiselTests/WireSpec.scala
@@ -0,0 +1,20 @@
+// See LICENSE for license details.
+
+package chiselTests
+
+import chisel3._
+
+class WireSpec extends ChiselFlatSpec {
+  "WireInit.apply" should "work" in {
+    assertCompiles("WireInit(UInt(4.W), 2.U)")
+  }
+  it should "allow DontCare" in {
+    assertCompiles("WireInit(UInt(4.W), DontCare)")
+  }
+  it should "not allow DontCare to affect type inference" in {
+    assertCompiles("val x: UInt = WireInit(UInt(4.W), DontCare)")
+  }
+  it should "not allow init argument to affect type inference" in {
+    assertDoesNotCompile("val x: UInt = WireInit(UInt(4.W), 2.S)")
+  }
+}
-- 
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