2 files changed, 23 insertions, 12 deletions
diff --git a/chiselFrontend/src/main/scala/chisel3/core/package.scala b/chiselFrontend/src/main/scala/chisel3/core/package.scala
index 1d5817ae..87dca1f3 100644
--- a/chiselFrontend/src/main/scala/chisel3/core/package.scala
+++ b/chiselFrontend/src/main/scala/chisel3/core/package.scala
@@ -55,14 +55,17 @@ package chisel3 {
     implicit class fromStringToLiteral(val str: String) {
       /** String to UInt parse, recommended style for constants.
         */
-      def U(): UInt = UInt.Lit(parse(str), parsedWidth(str))  // scalastyle:ignore method.name
+      def U(): UInt = str.asUInt() // scalastyle:ignore method.name
       /** String to UInt parse with specified width, recommended style for constants.
         */
-      def U(width: Width): UInt = UInt.Lit(parse(str), width)  // scalastyle:ignore method.name
+      def U(width: Width): UInt = str.asUInt(width) // scalastyle:ignore method.name
 
       /** String to UInt parse, recommended style for variables.
         */
-      def asUInt(): UInt = UInt.Lit(parse(str), parsedWidth(str))
+      def asUInt(): UInt = {
+        val bigInt = parse(str)
+        UInt.Lit(bigInt, Width(bigInt.bitLength max 1))
+      }
       /** String to UInt parse with specified width, recommended style for variables.
         */
       def asUInt(width: Width): UInt = UInt.Lit(parse(str), width)
@@ -78,15 +81,6 @@ package chisel3 {
         }
         BigInt(num.filterNot(_ == '_'), radix)
       }
-
-      protected def parsedWidth(n: String) =
-        if (n(0) == 'b') {
-          Width(n.length-1)
-        } else if (n(0) == 'h') {
-          Width((n.length-1) * 4)
-        } else {
-          Width()
-        }
     }
 
     implicit class fromBooleanToLiteral(val boolean: Boolean) {
diff --git a/src/test/scala/chiselTests/WidthSpec.scala b/src/test/scala/chiselTests/WidthSpec.scala
new file mode 100644
index 00000000..9a5b1860
--- /dev/null
+++ b/src/test/scala/chiselTests/WidthSpec.scala
@@ -0,0 +1,17 @@
+// See LICENSE for license details.
+
+package chiselTests
+
+import chisel3._
+
+class WidthSpec extends ChiselFlatSpec {
+  "Literals without specified widths" should "get the minimum legal width" in {
+    "hdeadbeef".U.getWidth should be (32)
+    "h_dead_beef".U.getWidth should be (32)
+    "h0a".U.getWidth should be (4)
+    "h1a".U.getWidth should be (5)
+    "h0".U.getWidth should be (1)
+    1.U.getWidth should be (1)
+    1.S.getWidth should be (2)
+  }
+}