5 files changed, 70 insertions, 18 deletions
diff --git a/core/src/main/scala/chisel3/Bits.scala b/core/src/main/scala/chisel3/Bits.scala
index a135a8e5..c914e88c 100644
--- a/core/src/main/scala/chisel3/Bits.scala
+++ b/core/src/main/scala/chisel3/Bits.scala
@@ -8,7 +8,13 @@ import chisel3.experimental.{FixedPoint, Interval}
 import chisel3.internal._
 import chisel3.internal.Builder.pushOp
 import chisel3.internal.firrtl._
-import chisel3.internal.sourceinfo.{SourceInfo, SourceInfoTransform, SourceInfoWhiteboxTransform, UIntTransform}
+import chisel3.internal.sourceinfo.{
+  IntLiteralApplyTransform,
+  SourceInfo,
+  SourceInfoTransform,
+  SourceInfoWhiteboxTransform,
+  UIntTransform
+}
 import chisel3.internal.firrtl.PrimOp._
 import _root_.firrtl.{ir => firrtlir}
 import _root_.firrtl.{constraint => firrtlconstraint}
@@ -94,7 +100,7 @@ sealed abstract class Bits(private[chisel3] val width: Width) extends Element wi
     * @param x an index
     * @return the specified bit
     */
-  final def apply(x: BigInt): Bool = macro SourceInfoTransform.xArg
+  final def apply(x: BigInt): Bool = macro IntLiteralApplyTransform.safeApply
 
   /** @group SourceInfoTransformMacro */
   final def do_apply(x: BigInt)(implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): Bool = {
@@ -121,12 +127,12 @@ sealed abstract class Bits(private[chisel3] val width: Width) extends Element wi
     *
     * @param x an index
     * @return the specified bit
-    * @note convenience method allowing direct use of [[scala.Int]] without implicits
     */
-  final def apply(x: Int): Bool = macro SourceInfoTransform.xArg
+  final def apply(x: Int): Bool = macro IntLiteralApplyTransform.safeApply
 
   /** @group SourceInfoTransformMacro */
-  final def do_apply(x: Int)(implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): Bool = apply(BigInt(x))
+  final def do_apply(x: Int)(implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): Bool =
+    do_apply(BigInt(x))
 
   /** Returns the specified bit on this wire as a [[Bool]], dynamically addressed.
     *
@@ -193,7 +199,7 @@ sealed abstract class Bits(private[chisel3] val width: Width) extends Element wi
 
   /** @group SourceInfoTransformMacro */
   final def do_apply(x: BigInt, y: BigInt)(implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): UInt =
-    apply(castToInt(x, "High index"), castToInt(y, "Low index"))
+    do_apply(castToInt(x, "High index"), castToInt(y, "Low index"))
 
   private[chisel3] def unop[T <: Data](sourceInfo: SourceInfo, dest: T, op: PrimOp): T = {
     requireIsHardware(this, "bits operated on")
diff --git a/core/src/main/scala/chisel3/package.scala b/core/src/main/scala/chisel3/package.scala
index 5521c51e..87024683 100644
--- a/core/src/main/scala/chisel3/package.scala
+++ b/core/src/main/scala/chisel3/package.scala
@@ -7,6 +7,8 @@ import scala.collection.mutable
 /** This package contains the main chisel3 API.
   */
 package object chisel3 {
+  import internal.chiselRuntimeDeprecated
+  import internal.sourceinfo.DeprecatedSourceInfo
   import internal.firrtl.{Port, Width}
   import internal.Builder
 
@@ -39,13 +41,11 @@ package object chisel3 {
       case bigint                => Builder.error(s"Cannot convert $bigint to Bool, must be 0 or 1"); Bool.Lit(false)
     }
 
-    /** Int to UInt conversion, recommended style for constants.
-      */
-    def U: UInt = UInt.Lit(bigint, Width())
+    /** Int to UInt conversion, recommended style for constants. */
+    def U: UInt = UInt.Lit(bigint, Width()) // scalastyle:ignore method.name
 
-    /** Int to SInt conversion, recommended style for constants.
-      */
-    def S: SInt = SInt.Lit(bigint, Width())
+    /** Int to SInt conversion, recommended style for constants. */
+    def S: SInt = SInt.Lit(bigint, Width()) // scalastyle:ignore method.name
 
     /** Int to UInt conversion with specified width, recommended style for constants.
       */
diff --git a/macros/src/main/scala/chisel3/internal/sourceinfo/SourceInfoTransform.scala b/macros/src/main/scala/chisel3/internal/sourceinfo/SourceInfoTransform.scala
index 3e310774..6c83da00 100644
--- a/macros/src/main/scala/chisel3/internal/sourceinfo/SourceInfoTransform.scala
+++ b/macros/src/main/scala/chisel3/internal/sourceinfo/SourceInfoTransform.scala
@@ -249,3 +249,31 @@ class SourceInfoWhiteboxTransform(val c: whitebox.Context) extends AutoSourceTra
     q"$thisObj.$doFuncTerm($that)($implicitSourceInfo, $implicitCompileOptions)"
   }
 }
+
+// Workaround for https://github.com/sbt/sbt/issues/3966
+object IntLiteralApplyTransform
+
+class IntLiteralApplyTransform(val c: Context) extends AutoSourceTransform {
+  import c.universe._
+
+  def safeApply(x: c.Tree): c.Tree = {
+    c.macroApplication match {
+      case q"$_.$clazz($lit).$func.apply($arg)" =>
+        if (
+          Set("U", "S").contains(func.toString) &&
+          Set("fromStringToLiteral", "fromIntToLiteral", "fromLongToIteral", "fromBigIntToLiteral").contains(
+            clazz.toString
+          )
+        ) {
+          val msg =
+            s"""Passing an Int to .$func is usually a mistake: It does *not* set the width but does a bit extract.
+               |Did you mean .$func($arg.W)?
+               |If you want to hide this message, assign .$func to a val first, then invoke .apply($arg)
+               |""".stripMargin
+          c.warning(c.enclosingPosition, msg)
+        }
+      case _ => // do nothing
+    }
+    q"$thisObj.$doFuncTerm($x)($implicitSourceInfo, $implicitCompileOptions)"
+  }
+}
diff --git a/src/test/scala/chiselTests/SIntOps.scala b/src/test/scala/chiselTests/SIntOps.scala
index 55b4c915..580a6e34 100644
--- a/src/test/scala/chiselTests/SIntOps.scala
+++ b/src/test/scala/chiselTests/SIntOps.scala
@@ -85,9 +85,18 @@ class SIntOpsTester(c: SIntOps) extends Tester(c) {
  */
 
 class SIntLitExtractTester extends BasicTester {
-  assert(-5.S(1) === true.B)
-  assert(-5.S(2) === false.B)
-  assert(-5.S(100) === true.B)
+  assert({
+    val lit = -5.S
+    lit(1) === true.B
+  })
+  assert({
+    val lit = -5.S
+    lit(2) === false.B
+  })
+  assert({
+    val lit = -5.S
+    lit(100) === true.B
+  })
   assert(-5.S(3, 0) === "b1011".U)
   assert(-5.S(9, 0) === "b1111111011".U)
   assert(-5.S(4.W)(1) === true.B)
diff --git a/src/test/scala/chiselTests/UIntOps.scala b/src/test/scala/chiselTests/UIntOps.scala
index 0010e9ac..6569c9e7 100644
--- a/src/test/scala/chiselTests/UIntOps.scala
+++ b/src/test/scala/chiselTests/UIntOps.scala
@@ -172,9 +172,18 @@ class MatchedRotateLeftAndRight(w: Int = 13) extends BasicTester {
 }
 
 class UIntLitExtractTester extends BasicTester {
-  assert("b101010".U(2) === false.B)
-  assert("b101010".U(3) === true.B)
-  assert("b101010".U(100) === false.B)
+  assert({
+    val lit = "b101010".U
+    lit(2) === false.B
+  })
+  assert({
+    val lit = "b101010".U
+    lit(3) === true.B
+  })
+  assert({
+    val lit = "b101010".U
+    lit(100) === false.B
+  })
   assert("b101010".U(3, 0) === "b1010".U)
   assert("b101010".U(9, 0) === "b0000101010".U)