Deprecate auto-application of empty argument lists to parameterless functions (#2124)

* Migrate nullary funcs to parameterless versions
* Make deprecation message and dummy arguments clear and consistent

Co-authored-by: Megan Wachs <megan@sifive.com>

14 files changed, 161 insertions, 62 deletions

diff --git a/core/src/main/scala/chisel3/Aggregate.scala b/core/src/main/scala/chisel3/Aggregate.scala
index 1892f7c2..4cf427ff 100644
--- a/core/src/main/scala/chisel3/Aggregate.scala
+++ b/core/src/main/scala/chisel3/Aggregate.scala
@@ -54,7 +54,7 @@ sealed abstract class Aggregate extends Data {
   override def litOption: Option[BigInt] = {
     // Shift the accumulated value by our width and add in our component, masked by our width.
     def shiftAdd(accumulator: Option[BigInt], elt: Data): Option[BigInt] = {
-      (accumulator, elt.litOption()) match {
+      (accumulator, elt.litOption) match {
         case (Some(accumulator), Some(eltLit)) =>
           val width = elt.width.get
           val masked = ((BigInt(1) << width) - 1) & eltLit  // also handles the negative case with two's complement
diff --git a/core/src/main/scala/chisel3/Bits.scala b/core/src/main/scala/chisel3/Bits.scala
index 670f6e7a..b7a4a1a7 100644
--- a/core/src/main/scala/chisel3/Bits.scala
+++ b/core/src/main/scala/chisel3/Bits.scala
@@ -25,7 +25,10 @@ private[chisel3] sealed trait ToBoolable extends Element {
     *
     * @note The width must be known and equal to 1
     */
-  final def asBool(): Bool = macro SourceInfoWhiteboxTransform.noArg
+  final def asBool: Bool = macro SourceInfoWhiteboxTransform.noArg
+
+  @deprecated("Calling this function with an empty argument list is invalid in Scala 3. Use the form without parentheses instead", "Chisel 3.5")
+  final def asBool(dummy: Int*): Bool = macro SourceInfoWhiteboxTransform.noArgDummy
 
   /** @group SourceInfoTransformMacro */
   def do_asBool(implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): Bool
@@ -222,7 +225,10 @@ sealed abstract class Bits(private[chisel3] val width: Width) extends Element wi
     * @return this $coll with each bit inverted
     * @group Bitwise
     */
-  final def unary_~ (): Bits = macro SourceInfoWhiteboxTransform.noArg
+  final def unary_~ : Bits = macro SourceInfoWhiteboxTransform.noArg
+
+  @deprecated("Calling this function with an empty argument list is invalid in Scala 3. Use the form without parentheses instead", "Chisel 3.5")
+  final def unary_~(dummy: Int*): Bits = macro SourceInfoWhiteboxTransform.noArgDummy
 
   /** @group SourceInfoTransformMacro */
   def do_unary_~ (implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): Bits
@@ -304,10 +310,16 @@ sealed abstract class Bits(private[chisel3] val width: Width) extends Element wi
   def do_>> (that: UInt)(implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): Bits
 
   /** Returns the contents of this wire as a [[scala.collection.Seq]] of [[Bool]]. */
-  final def toBools(): Seq[Bool] = macro SourceInfoTransform.noArg
+  final def toBools: Seq[Bool] = macro SourceInfoTransform.noArg
+
+  @deprecated("Calling this function with an empty argument list is invalid in Scala 3. Use the form without parentheses instead", "Chisel 3.5")
+  final def toBools(dummy: Int*): Seq[Bool] = macro SourceInfoWhiteboxTransform.noArgDummy
 
   /** Returns the contents of this wire as a [[scala.collection.Seq]] of [[Bool]]. */
-  final def asBools(): Seq[Bool] = macro SourceInfoTransform.noArg
+  final def asBools: Seq[Bool] = macro SourceInfoTransform.noArg
+
+  @deprecated("Calling this function with an empty argument list is invalid in Scala 3. Use the form without parentheses instead", "Chisel 3.5")
+  final def asBools(dummy: Int*): Seq[Bool] = macro SourceInfoWhiteboxTransform.noArgDummy
 
   /** @group SourceInfoTransformMacro */
   def do_asBools(implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): Seq[Bool] =
@@ -318,7 +330,10 @@ sealed abstract class Bits(private[chisel3] val width: Width) extends Element wi
     * @note The arithmetic value is not preserved if the most-significant bit is set. For example, a [[UInt]] of
     * width 3 and value 7 (0b111) would become an [[SInt]] of width 3 and value -1.
     */
-  final def asSInt(): SInt = macro SourceInfoTransform.noArg
+  final def asSInt: SInt = macro SourceInfoTransform.noArg
+
+  @deprecated("Calling this function with an empty argument list is invalid in Scala 3. Use the form without parentheses instead", "Chisel 3.5")
+  final def asSInt(dummy: Int*): SInt = macro SourceInfoWhiteboxTransform.noArgDummy
 
   /** @group SourceInfoTransformMacro */
   def do_asSInt(implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): SInt
@@ -410,7 +425,10 @@ sealed class UInt private[chisel3] (width: Width) extends Bits(width) with Num[U
     * $constantWidth
     * @group Arithmetic
     */
-  final def unary_- (): UInt = macro SourceInfoTransform.noArg
+  final def unary_- : UInt = macro SourceInfoTransform.noArg
+
+  @deprecated("Calling this function with an empty argument list is invalid in Scala 3. Use the form without parentheses instead", "Chisel 3.5")
+  final def unary_-(dummy: Int*): UInt = macro SourceInfoTransform.noArgDummy
 
   /** Unary negation (constant width)
     *
@@ -418,7 +436,10 @@ sealed class UInt private[chisel3] (width: Width) extends Bits(width) with Num[U
     * $constantWidth
     * @group Arithmetic
     */
-  final def unary_-% (): UInt = macro SourceInfoTransform.noArg
+  final def unary_-% : UInt = macro SourceInfoTransform.noArg
+
+  @deprecated("Calling this function with an empty argument list is invalid in Scala 3. Use the form without parentheses instead", "Chisel 3.5")
+  final def unary_%(dummy: Int*): UInt = macro SourceInfoTransform.noArgDummy
 
   /** @group SourceInfoTransformMacro */
   def do_unary_- (implicit sourceInfo: SourceInfo, compileOptions: CompileOptions) : UInt = 0.U - this
@@ -522,7 +543,7 @@ sealed class UInt private[chisel3] (width: Width) extends Bits(width) with Num[U
     */
   final def ^ (that: UInt): UInt = macro SourceInfoTransform.thatArg
 
-  //  override def abs: UInt = macro SourceInfoTransform.noArg
+  //  override def abs: UInt = macro SourceInfoTransform.noArgDummy
   def do_abs(implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): UInt = this
 
   /** @group SourceInfoTransformMacro */
@@ -545,21 +566,30 @@ sealed class UInt private[chisel3] (width: Width) extends Bits(width) with Num[U
     * @return a hardware [[Bool]] resulting from every bit of this $coll or'd together
     * @group Bitwise
     */
-  final def orR(): Bool = macro SourceInfoTransform.noArg
+  final def orR: Bool = macro SourceInfoTransform.noArg
+
+  @deprecated("Calling this function with an empty argument list is invalid in Scala 3. Use the form without parentheses instead", "Chisel 3.5")
+  final def orR(dummy: Int*): Bool = macro SourceInfoTransform.noArgDummy
 
   /** And reduction operator
     *
     * @return a hardware [[Bool]] resulting from every bit of this $coll and'd together
     * @group Bitwise
     */
-  final def andR(): Bool = macro SourceInfoTransform.noArg
+  final def andR: Bool = macro SourceInfoTransform.noArg
+
+  @deprecated("Calling this function with an empty argument list is invalid in Scala 3. Use the form without parentheses instead", "Chisel 3.5")
+  final def andR(dummy: Int*): Bool = macro SourceInfoTransform.noArgDummy
 
   /** Exclusive or (xor) reduction operator
     *
     * @return a hardware [[Bool]] resulting from every bit of this $coll xor'd together
     * @group Bitwise
     */
-  final def xorR(): Bool = macro SourceInfoTransform.noArg
+  final def xorR: Bool = macro SourceInfoTransform.noArg
+
+  @deprecated("Calling this function with an empty argument list is invalid in Scala 3. Use the form without parentheses instead", "Chisel 3.5")
+  final def xorR(dummy: Int*): Bool = macro SourceInfoTransform.noArgDummy
 
   /** @group SourceInfoTransformMacro */
   def do_orR(implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): Bool = redop(sourceInfo, OrReduceOp)
@@ -599,7 +629,10 @@ sealed class UInt private[chisel3] (width: Width) extends Bits(width) with Num[U
     * @return a hardware [[Bool]] asserted if this $coll equals zero
     * @group Bitwise
     */
-  final def unary_! () : Bool = macro SourceInfoTransform.noArg
+  final def unary_! : Bool = macro SourceInfoTransform.noArg
+
+  @deprecated("Calling this function with an empty argument list is invalid in Scala 3. Use the form without parentheses instead", "Chisel 3.5")
+  final def unary_! (dummy: Int*): Bool = macro SourceInfoTransform.noArgDummy
 
   /** @group SourceInfoTransformMacro */
   def do_unary_! (implicit sourceInfo: SourceInfo, compileOptions: CompileOptions) : Bool = this === 0.U(1.W)
@@ -639,7 +672,11 @@ sealed class UInt private[chisel3] (width: Width) extends Bits(width) with Num[U
     * @return an [[SInt]] equal to this $coll with an additional zero in its most significant bit
     * @note The width of the returned [[SInt]] is `width of this` + `1`.
     */
-  final def zext(): SInt = macro SourceInfoTransform.noArg
+  final def zext: SInt = macro SourceInfoTransform.noArg
+
+  @deprecated("Calling this function with an empty argument list is invalid in Scala 3. Use the form without parentheses instead", "Chisel 3.5")
+  final def zext(dummy: Int*): SInt = macro SourceInfoTransform.noArgDummy
+
   /** @group SourceInfoTransformMacro */
   def do_zext(implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): SInt =
     pushOp(DefPrim(sourceInfo, SInt(width + 1), ConvertOp, ref))
@@ -716,7 +753,10 @@ sealed class SInt private[chisel3] (width: Width) extends Bits(width) with Num[S
     * $constantWidth
     * @group Arithmetic
     */
-  final def unary_- (): SInt = macro SourceInfoTransform.noArg
+  final def unary_- : SInt = macro SourceInfoTransform.noArg
+
+  @deprecated("Calling this function with an empty argument list is invalid in Scala 3. Use the form without parentheses instead", "Chisel 3.5")
+  final def unary_-(dummy: Int*): SInt = macro SourceInfoTransform.noArgDummy
 
   /** Unary negation (constant width)
     *
@@ -724,12 +764,15 @@ sealed class SInt private[chisel3] (width: Width) extends Bits(width) with Num[S
     * $constantWidth
     * @group Arithmetic
     */
-  final def unary_-% (): SInt = macro SourceInfoTransform.noArg
+  final def unary_-% : SInt = macro SourceInfoTransform.noArg
+
+  @deprecated("Calling this function with an empty argument list is invalid in Scala 3. Use the form without parentheses instead", "Chisel 3.5")
+  final def unary_-%(dummy: Int*): SInt = macro SourceInfoTransform.noArgDummy
 
   /** @group SourceInfoTransformMacro */
-  def unary_- (implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): SInt = 0.S - this
+  def do_unary_- (implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): SInt = 0.S - this
   /** @group SourceInfoTransformMacro */
-  def unary_-% (implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): SInt = 0.S -% this
+  def do_unary_-% (implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): SInt = 0.S -% this
 
   /** add (default - no growth) operator */
   override def do_+ (that: SInt)(implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): SInt =
@@ -755,7 +798,7 @@ sealed class SInt private[chisel3] (width: Width) extends Bits(width) with Num[S
   final def * (that: UInt): SInt = macro SourceInfoTransform.thatArg
   /** @group SourceInfoTransformMacro */
   def do_* (that: UInt)(implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): SInt = {
-    val thatToSInt = that.zext()
+    val thatToSInt = that.zext
     val result = binop(sourceInfo, SInt(this.width + thatToSInt.width), TimesOp, thatToSInt)
     result.tail(1).asSInt
   }
@@ -876,10 +919,10 @@ sealed class SInt private[chisel3] (width: Width) extends Bits(width) with Num[S
   /** @group SourceInfoTransformMacro */
   def do_=== (that: SInt)(implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): Bool = compop(sourceInfo, EqualOp, that)
 
-//  final def abs(): UInt = macro SourceInfoTransform.noArg
+//  final def abs(): UInt = macro SourceInfoTransform.noArgDummy
 
   def do_abs(implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): SInt = {
-    Mux(this < 0.S, (-this), this)
+    Mux(this < 0.S, -this, this)
   }
 
   override def do_<< (that: Int)(implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): SInt =
@@ -938,7 +981,10 @@ sealed class SInt private[chisel3] (width: Width) extends Bits(width) with Num[S
 
 sealed trait Reset extends Element with ToBoolable {
   /** Casts this $coll to an [[AsyncReset]] */
-  final def asAsyncReset(): AsyncReset = macro SourceInfoWhiteboxTransform.noArg
+  final def asAsyncReset: AsyncReset = macro SourceInfoWhiteboxTransform.noArg
+
+  @deprecated("Calling this function with an empty argument list is invalid in Scala 3. Use the form without parentheses instead", "Chisel 3.5")
+  final def asAsyncReset(dummy: Int*): AsyncReset = macro SourceInfoTransform.noArgDummy
 
   /** @group SourceInfoTransformMacro */
   def do_asAsyncReset(implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): AsyncReset
@@ -1124,7 +1170,10 @@ sealed class Bool() extends UInt(1.W) with Reset {
   def do_&& (that: Bool)(implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): Bool = this & that
 
   /** Reinterprets this $coll as a clock */
-  def asClock(): Clock = macro SourceInfoTransform.noArg
+  def asClock: Clock = macro SourceInfoTransform.noArg
+
+  @deprecated("Calling this function with an empty argument list is invalid in Scala 3. Use the form without parentheses instead", "Chisel 3.5")
+  def asClock(dummy: Int*): Clock = macro SourceInfoTransform.noArgDummy
 
   /** @group SourceInfoTransformMacro */
   def do_asClock(implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): Clock = pushOp(DefPrim(sourceInfo, Clock(), AsClockOp, ref))
@@ -1220,7 +1269,10 @@ package experimental {
       *         $expandingWidth
       * @group Arithmetic
       */
-    final def unary_- (): FixedPoint = macro SourceInfoTransform.noArg
+    final def unary_- : FixedPoint = macro SourceInfoTransform.noArg
+
+    @deprecated("Calling this function with an empty argument list is invalid in Scala 3. Use the form without parentheses instead", "Chisel 3.5")
+    final def unary_-(dummy: Int*): FixedPoint = macro SourceInfoTransform.noArgDummy
 
     /** Unary negation (constant width)
       *
@@ -1228,7 +1280,9 @@ package experimental {
       *         $constantWidth
       * @group Arithmetic
       */
-    final def unary_-% (): FixedPoint = macro SourceInfoTransform.noArg
+    final def unary_-% : FixedPoint = macro SourceInfoTransform.noArg
+    @deprecated("Calling this function with an empty argument list is invalid in Scala 3. Use the form without parentheses instead", "Chisel 3.5")
+    final def unary_-%(dummy: Int*): FixedPoint = macro SourceInfoTransform.noArgDummy
 
     /** @group SourceInfoTransformMacro */
     def unary_- (implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): FixedPoint = FixedPoint.fromBigInt(0) - this
@@ -1663,8 +1717,15 @@ package experimental {
       }
     }
 
-    final def unary_-(): Interval = macro SourceInfoTransform.noArg
-    final def unary_-%(): Interval = macro SourceInfoTransform.noArg
+    final def unary_- : Interval = macro SourceInfoTransform.noArg
+
+    @deprecated("Calling this function with an empty argument list is invalid in Scala 3. Use the form without parentheses instead", "Chisel 3.5")
+    final def unary_-(dummy: Int*): Interval = macro SourceInfoTransform.noArgDummy
+
+    final def unary_-% : Interval = macro SourceInfoTransform.noArg
+
+    @deprecated("Calling this function with an empty argument list is invalid in Scala 3. Use the form without parentheses instead", "Chisel 3.5")
+    final def unary_-%(dummy: Int*): Interval = macro SourceInfoTransform.noArgDummy
 
     def unary_-(implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): Interval = {
       Interval.Zero - this
@@ -1779,7 +1840,7 @@ package experimental {
     def do_=/= (that: Interval)(implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): Bool = compop(sourceInfo, NotEqualOp, that)
     def do_=== (that: Interval)(implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): Bool = compop(sourceInfo, EqualOp, that)
 
-    //  final def abs(): UInt = macro SourceInfoTransform.noArg
+    //  final def abs(): UInt = macro SourceInfoTransform.noArgDummy
 
     def do_abs(implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): Interval = {
       Mux(this < Interval.Zero, (Interval.Zero - this), this)
diff --git a/core/src/main/scala/chisel3/Clock.scala b/core/src/main/scala/chisel3/Clock.scala
index edb07908..0400697d 100644
--- a/core/src/main/scala/chisel3/Clock.scala
+++ b/core/src/main/scala/chisel3/Clock.scala
@@ -32,8 +32,12 @@ sealed class Clock(private[chisel3] val width: Width = Width(1)) extends Element
   def toPrintable: Printable = PString("CLOCK")
 
   /** Returns the contents of the clock wire as a [[Bool]]. */
-  final def asBool(): Bool = macro SourceInfoTransform.noArg
-  def do_asBool(implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): Bool = this.asUInt().asBool()
+  final def asBool: Bool = macro SourceInfoTransform.noArg
+
+  @deprecated("Calling this function with an empty argument list is invalid in Scala 3. Use the form without parentheses instead", "Chisel 3.5")
+  final def asBool(dummy: Int*): Bool = macro SourceInfoTransform.noArgDummy
+
+  def do_asBool(implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): Bool = this.asUInt.asBool
 
   override def do_asUInt(implicit sourceInfo: SourceInfo, connectCompileOptions: CompileOptions): UInt = pushOp(DefPrim(sourceInfo, UInt(this.width), AsUIntOp, ref))
   private[chisel3] override def connectFromBits(that: Bits)(implicit sourceInfo: SourceInfo,
diff --git a/core/src/main/scala/chisel3/Data.scala b/core/src/main/scala/chisel3/Data.scala
index 32d83008..4ae29ce8 100644
--- a/core/src/main/scala/chisel3/Data.scala
+++ b/core/src/main/scala/chisel3/Data.scala
@@ -645,18 +645,28 @@ abstract class Data extends HasId with NamedComponent with SourceInfoDoc {
     }
   }
 
-  def isLit(): Boolean = litOption.isDefined
+  def isLit: Boolean = litOption.isDefined
+
+  @deprecated("Calling this function with an empty argument list is invalid in Scala 3. Use the form without parentheses instead", "Chisel 3.5")
+  def isLit(dummy: Int*): Boolean = isLit
+
 
   /**
    * If this is a literal that is representable as bits, returns the value as a BigInt.
    * If not a literal, or not representable as bits (for example, is or contains Analog), returns None.
    */
-  def litOption(): Option[BigInt]
+  def litOption: Option[BigInt]
+
+  @deprecated("Calling this function with an empty argument list is invalid in Scala 3. Use the form without parentheses instead", "Chisel 3.5")
+  def litOption(dummy: Int*): Option[BigInt] = litOption
 
   /**
    * Returns the literal value if this is a literal that is representable as bits, otherwise crashes.
    */
-  def litValue(): BigInt = litOption.get
+  def litValue: BigInt = litOption.get
+
+  @deprecated("Calling this function with an empty argument list is invalid in Scala 3. Use the form without parentheses instead", "Chisel 3.5")
+  def litValue(dummy: Int*): BigInt = litValue
 
   /** Returns the width, in bits, if currently known. */
   final def getWidth: Int =
@@ -679,7 +689,7 @@ abstract class Data extends HasId with NamedComponent with SourceInfoDoc {
   /** @group SourceInfoTransformMacro */
   def do_asTypeOf[T <: Data](that: T)(implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): T = {
     val thatCloned = Wire(that.cloneTypeFull)
-    thatCloned.connectFromBits(this.asUInt())
+    thatCloned.connectFromBits(this.asUInt)
     thatCloned
   }
 
@@ -695,7 +705,10 @@ abstract class Data extends HasId with NamedComponent with SourceInfoDoc {
     * @note Aggregates are recursively packed with the first element appearing
     * in the least-significant bits of the result.
     */
-  final def asUInt(): UInt = macro SourceInfoTransform.noArg
+  final def asUInt: UInt = macro SourceInfoTransform.noArg
+
+  @deprecated("Calling this function with an empty argument list is invalid in Scala 3. Use the form without parentheses instead", "Chisel 3.5")
+  final def asUInt(dummy: Int*): UInt = macro SourceInfoTransform.noArgDummy
 
   /** @group SourceInfoTransformMacro */
   def do_asUInt(implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): UInt
@@ -715,7 +728,7 @@ trait WireFactory {
     val x = t.cloneTypeFull
 
     // Bind each element of x to being a Wire
-    x.bind(WireBinding(Builder.forcedUserModule, Builder.currentWhen()))
+    x.bind(WireBinding(Builder.forcedUserModule, Builder.currentWhen))
 
     pushCommand(DefWire(sourceInfo, x))
     if (!compileOptions.explicitInvalidate) {
diff --git a/core/src/main/scala/chisel3/Mem.scala b/core/src/main/scala/chisel3/Mem.scala
index 183620b6..aeacf052 100644
--- a/core/src/main/scala/chisel3/Mem.scala
+++ b/core/src/main/scala/chisel3/Mem.scala
@@ -130,7 +130,7 @@ sealed abstract class MemBase[T <: Data](val t: T, val length: BigInt) extends H
        t.cloneTypeFull, Node(this), dir, i.ref, Builder.forcedClock.ref)
     ).id
     // Bind each element of port to being a MemoryPort
-    port.bind(MemoryPortBinding(Builder.forcedUserModule, Builder.currentWhen()))
+    port.bind(MemoryPortBinding(Builder.forcedUserModule, Builder.currentWhen))
     port
   }
 }
diff --git a/core/src/main/scala/chisel3/Module.scala b/core/src/main/scala/chisel3/Module.scala
index 3ae48821..56dce4d5 100644
--- a/core/src/main/scala/chisel3/Module.scala
+++ b/core/src/main/scala/chisel3/Module.scala
@@ -39,7 +39,7 @@ object Module extends SourceInfoDoc {
 
     // Save then clear clock and reset to prevent leaking scope, must be set again in the Module
     val (saveClock, saveReset)  = (Builder.currentClock, Builder.currentReset)
-    val savePrefix = Builder.getPrefix()
+    val savePrefix = Builder.getPrefix
     Builder.clearPrefix()
     Builder.currentClock = None
     Builder.currentReset = None
diff --git a/core/src/main/scala/chisel3/Num.scala b/core/src/main/scala/chisel3/Num.scala
index 6dd299f4..219e18f4 100644
--- a/core/src/main/scala/chisel3/Num.scala
+++ b/core/src/main/scala/chisel3/Num.scala
@@ -148,7 +148,10 @@ trait Num[T <: Data] {
     * $unchangedWidth
     * @group Arithmetic
     */
-  final def abs(): T = macro SourceInfoTransform.noArg
+  final def abs: T = macro SourceInfoTransform.noArg
+
+  @deprecated("Calling this function with an empty argument list is invalid in Scala 3. Use the form without parentheses instead", "Chisel 3.5")
+  final def abs(dummy: Int*): T = macro SourceInfoTransform.noArgDummy
 
   /** @group SourceInfoTransformMacro */
   def do_abs(implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): T
diff --git a/core/src/main/scala/chisel3/Reg.scala b/core/src/main/scala/chisel3/Reg.scala
index bd9e5311..122c5ebd 100644
--- a/core/src/main/scala/chisel3/Reg.scala
+++ b/core/src/main/scala/chisel3/Reg.scala
@@ -41,7 +41,7 @@ object Reg {
     val reg = t.cloneTypeFull
     val clock = Node(Builder.forcedClock)
 
-    reg.bind(RegBinding(Builder.forcedUserModule, Builder.currentWhen()))
+    reg.bind(RegBinding(Builder.forcedUserModule, Builder.currentWhen))
     pushCommand(DefReg(sourceInfo, reg, clock))
     reg
   }
@@ -174,7 +174,7 @@ object RegInit {
     val clock = Builder.forcedClock
     val reset = Builder.forcedReset
 
-    reg.bind(RegBinding(Builder.forcedUserModule, Builder.currentWhen()))
+    reg.bind(RegBinding(Builder.forcedUserModule, Builder.currentWhen))
     requireIsHardware(init, "reg initializer")
     pushCommand(DefRegInit(sourceInfo, reg, clock.ref, reset.ref, init.ref))
     reg
diff --git a/core/src/main/scala/chisel3/SeqUtils.scala b/core/src/main/scala/chisel3/SeqUtils.scala
index da6fc802..5c86efd3 100644
--- a/core/src/main/scala/chisel3/SeqUtils.scala
+++ b/core/src/main/scala/chisel3/SeqUtils.scala
@@ -81,7 +81,7 @@ private[chisel3] object SeqUtils {
       val output = cloneSupertype(in.toSeq map { _._2}, "oneHotMux")
 
       def buildAndOrMultiplexor[TT <: Data](inputs: Iterable[(Bool, TT)]): T = {
-        val masked = for ((s, i) <- inputs) yield Mux(s, i.asUInt(), 0.U)
+        val masked = for ((s, i) <- inputs) yield Mux(s, i.asUInt, 0.U)
         masked.reduceLeft(_ | _).asTypeOf(output)
       }
 
diff --git a/core/src/main/scala/chisel3/StrongEnum.scala b/core/src/main/scala/chisel3/StrongEnum.scala
index b3d7cf7d..9ae4c889 100644
--- a/core/src/main/scala/chisel3/StrongEnum.scala
+++ b/core/src/main/scala/chisel3/StrongEnum.scala
@@ -246,7 +246,7 @@ abstract class EnumFactory {
   private val enumRecords = mutable.ArrayBuffer.empty[EnumRecord]
 
   private def enumNames = enumRecords.map(_.name).toSeq
-  private def enumValues = enumRecords.map(_.inst.litValue()).toSeq
+  private def enumValues = enumRecords.map(_.inst.litValue).toSeq
   private def enumInstances = enumRecords.map(_.inst).toSeq
 
   private[chisel3] val enumTypeName = getClass.getName.init
@@ -265,7 +265,7 @@ abstract class EnumFactory {
   def all: Seq[Type] = enumInstances
 
   private[chisel3] def nameOfValue(id: BigInt): Option[String] = {
-    enumRecords.find(_.inst.litValue() == id).map(_.name)
+    enumRecords.find(_.inst.litValue == id).map(_.name)
   }
 
   protected def Value: Type = macro EnumMacros.ValImpl
@@ -291,11 +291,11 @@ abstract class EnumFactory {
     if (id.litOption.isEmpty) {
       throwException(s"$enumTypeName defined with a non-literal type")
     }
-    if (id.litValue() < this.id) {
+    if (id.litValue < this.id) {
       throwException(s"Enums must be strictly increasing: $enumTypeName")
     }
 
-    this.id = id.litValue()
+    this.id = id.litValue
     do_Value(name)
   }
 
diff --git a/core/src/main/scala/chisel3/When.scala b/core/src/main/scala/chisel3/When.scala
index a2c20d9a..ca383c0f 100644
--- a/core/src/main/scala/chisel3/When.scala
+++ b/core/src/main/scala/chisel3/When.scala
@@ -50,7 +50,7 @@ object when {
     implicit val sourceInfo = UnlocatableSourceInfo
     val whens = Builder.whenStack
     whens.foldRight(true.B) {
-      case (ctx, acc) => acc && ctx.localCond()
+      case (ctx, acc) => acc && ctx.localCond
     }
   }
 }
@@ -81,7 +81,7 @@ final class WhenContext private[chisel3] (
   private var scopeOpen = false
 
   /** Returns the local condition, inverted for an otherwise */
-  private[chisel3] def localCond(): Bool = {
+  private[chisel3] def localCond: Bool = {
     implicit val compileOptions = ExplicitCompileOptions.Strict
     implicit val sourceInfo = UnlocatableSourceInfo
     val alt = altConds.foldRight(true.B) {
@@ -111,7 +111,10 @@ final class WhenContext private[chisel3] (
   def otherwise(block: => Any)(implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): Unit =
     new WhenContext(sourceInfo, None, block, firrtlDepth + 1, cond ++: altConds)
 
-  def active(): Boolean = scopeOpen
+  def active: Boolean = scopeOpen
+
+  @deprecated("Calling this function with an empty argument list is invalid in Scala 3. Use the form without parentheses instead", "Chisel 3.5")
+  def active(dummy: Int*): Boolean = active
 
   /*
    *
diff --git a/core/src/main/scala/chisel3/internal/Builder.scala b/core/src/main/scala/chisel3/internal/Builder.scala
index 441abc92..4e68623d 100644
--- a/core/src/main/scala/chisel3/internal/Builder.scala
+++ b/core/src/main/scala/chisel3/internal/Builder.scala
@@ -105,7 +105,7 @@ private[chisel3] trait HasId extends InstanceId {
   private var auto_seed: Option[String] = None
 
   // Prefix at time when this class is constructed
-  private val construction_prefix: Prefix = Builder.getPrefix()
+  private val construction_prefix: Prefix = Builder.getPrefix
 
   // Prefix when the latest [[suggestSeed]] or [[autoSeed]] is called
   private var prefix_seed: Prefix = Nil
@@ -133,7 +133,7 @@ private[chisel3] trait HasId extends InstanceId {
   private[chisel3] def forceAutoSeed(seed: String): this.type = {
     auto_seed = Some(seed)
     for(hook <- auto_postseed_hooks) { hook(seed) }
-    prefix_seed = Builder.getPrefix()
+    prefix_seed = Builder.getPrefix
     this
   }
 
@@ -149,7 +149,7 @@ private[chisel3] trait HasId extends InstanceId {
     */
   def suggestName(seed: =>String): this.type = {
     if(suggested_seed.isEmpty) suggested_seed = Some(seed)
-    prefix_seed = Builder.getPrefix()
+    prefix_seed = Builder.getPrefix
     for(hook <- suggest_postseed_hooks) { hook(seed) }
     this
   }
@@ -485,7 +485,7 @@ private[chisel3] object Builder extends LazyLogging {
   }
 
   // Returns the prefix stack at this moment
-  def getPrefix(): Prefix = chiselContext.get().prefixStack
+  def getPrefix: Prefix = chiselContext.get().prefixStack
 
   def currentModule: Option[BaseModule] = dynamicContextVar.value match {
     case Some(dyanmicContext) => dynamicContext.currentModule
@@ -572,7 +572,7 @@ private[chisel3] object Builder extends LazyLogging {
     dynamicContext.whenStack = s
   }
 
-  def currentWhen(): Option[WhenContext] = dynamicContext.whenStack.headOption
+  def currentWhen: Option[WhenContext] = dynamicContext.whenStack.headOption
 
   def currentClock: Option[Clock] = dynamicContext.currentClock
   def currentClock_=(newClock: Option[Clock]): Unit = {
@@ -615,7 +615,7 @@ private[chisel3] object Builder extends LazyLogging {
   }
   def pushOp[T <: Data](cmd: DefPrim[T]): T = {
     // Bind each element of the returned Data to being a Op
-    cmd.id.bind(OpBinding(forcedUserModule, currentWhen()))
+    cmd.id.bind(OpBinding(forcedUserModule, currentWhen))
     pushCommand(cmd).id
   }
 
diff --git a/core/src/main/scala/chisel3/internal/prefix.scala b/core/src/main/scala/chisel3/internal/prefix.scala
index 9dc14901..620d0864 100644
--- a/core/src/main/scala/chisel3/internal/prefix.scala
+++ b/core/src/main/scala/chisel3/internal/prefix.scala
@@ -51,7 +51,7 @@ private[chisel3] object prefix { // scalastyle:ignore
     // This causes extra prefixes to be added, and subsequently cleared in the
     // Module constructor. Thus, we need to just make sure if the previous push
     // was an incorrect one, to not pop off an empty stack
-    if(Builder.getPrefix().nonEmpty) Builder.popPrefix()
+    if(Builder.getPrefix.nonEmpty) Builder.popPrefix()
     ret
   }
 }
@@ -77,7 +77,7 @@ private[chisel3] object noPrefix {
     * @return The return value of the provided function
     */
   def apply[T](f: => T): T = {
-    val prefix = Builder.getPrefix()
+    val prefix = Builder.getPrefix
     Builder.clearPrefix()
     val ret = f
     Builder.setPrefix(prefix)
diff --git a/core/src/main/scala/chisel3/package.scala b/core/src/main/scala/chisel3/package.scala
index 64cfa8b9..68e482dd 100644
--- a/core/src/main/scala/chisel3/package.scala
+++ b/core/src/main/scala/chisel3/package.scala
@@ -50,10 +50,18 @@ package object chisel3 {
 
     /** Int to UInt conversion, recommended style for variables.
       */
-    def asUInt(): UInt = UInt.Lit(bigint, Width())
+    def asUInt: UInt = UInt.Lit(bigint, Width())
+
+    @deprecated("Calling this function with an empty argument list is invalid in Scala 3. Use the form without parentheses instead", "Chisel 3.5")
+    def asUInt(dummy: Int*): UInt = asUInt
+
     /** Int to SInt conversion, recommended style for variables.
       */
-    def asSInt(): SInt = SInt.Lit(bigint, Width())
+    def asSInt: SInt = SInt.Lit(bigint, Width())
+
+    @deprecated("Calling this function with an empty argument list is invalid in Scala 3. Use the form without parentheses instead", "Chisel 3.5")
+    def asSInt(dummy: Int*): SInt = asSInt
+
     /** Int to UInt conversion with specified width, recommended style for variables.
       */
     def asUInt(width: Width): UInt = UInt.Lit(bigint, width)
@@ -68,17 +76,21 @@ package object chisel3 {
   implicit class fromStringToLiteral(str: String) {
     /** String to UInt parse, recommended style for constants.
       */
-    def U: UInt = str.asUInt()
+    def U: UInt = str.asUInt
     /** String to UInt parse with specified width, recommended style for constants.
       */
     def U(width: Width): UInt = str.asUInt(width)
 
     /** String to UInt parse, recommended style for variables.
       */
-    def asUInt(): UInt = {
+    def asUInt: UInt = {
       val bigInt = parse(str)
       UInt.Lit(bigInt, Width(bigInt.bitLength max 1))
     }
+
+    @deprecated("Calling this function with an empty argument list is invalid in Scala 3. Use the form without parentheses instead", "Chisel 3.5")
+    def asUInt(dummy: Int*): UInt = asUInt
+
     /** String to UInt parse with specified width, recommended style for variables.
       */
     def asUInt(width: Width): UInt = UInt.Lit(parse(str), width)
@@ -107,7 +119,10 @@ package object chisel3 {
 
     /** Boolean to Bool conversion, recommended style for variables.
       */
-    def asBool(): Bool = Bool.Lit(boolean)
+    def asBool: Bool = Bool.Lit(boolean)
+
+    @deprecated("Calling this function with an empty argument list is invalid in Scala 3. Use the form without parentheses instead", "Chisel 3.5")
+    def asBool(dummy: Int*): Bool = asBool
   }
 
   // Fixed Point is experimental for now, but we alias the implicit conversion classes here