Intrinsify scala.compiletime.code

Author: nicolasstucki

compiler/src/dotty/tools/dotc/core/Definitions.scala

@@ -224,6 +224,7 @@ class Definitions {
   @tu lazy val ScalaXmlPackageClass: Symbol = getPackageClassIfDefined("scala.xml")
 
   @tu lazy val CompiletimePackageObject: Symbol = requiredModule("scala.compiletime.package")
+    @tu lazy val Compiletime_code: Symbol = CompiletimePackageObject.requiredMethod("code")
     @tu lazy val Compiletime_erasedValue  : Symbol = CompiletimePackageObject.requiredMethod("erasedValue")
     @tu lazy val Compiletime_error        : Symbol = CompiletimePackageObject.requiredMethod(nme.error)
     @tu lazy val Compiletime_requireConst: Symbol = CompiletimePackageObject.requiredMethod("requireConst")

compiler/src/dotty/tools/dotc/typer/Inliner.scala

@@ -332,6 +332,28 @@ object Inliner {
     def typeCheckErrors(tree: Tree)(using Context): Tree =
       val errors = compileForErrors(tree, false)
       packErrors(errors)
+
+    def code(strCtx: Tree, argsTree: Tree, pos: SrcPos)(using Context): Tree =
+      object Consts:
+        def unapply(trees: List[Tree]): Option[List[String]] =
+          trees match
+            case Nil => Some(Nil)
+            case Literal(Constant(part: String)) :: Consts(rest) => Some(part :: rest)
+            case _ => None
+      strCtx match
+        case Apply(stringContextApply, List(Typed(SeqLiteral(Consts(parts), _), _)))
+        if stringContextApply.symbol == defn.StringContextModule_apply =>
+          argsTree match
+            case Typed(SeqLiteral(args, _), _) =>
+              val argStrs = args.map(_.show)
+              val showed = StringContext(parts: _*).s(argStrs: _*)
+              Literal(Constant(showed)).withSpan(pos.span)
+            case _ =>
+              report.error("Exprected explicit arguments to code", strCtx.srcPos)
+              ref(defn.Predef_undefined)
+        case _ =>
+          report.error("Exprected StringContext.apply with explicit `parts` arguments", strCtx.srcPos)
+          ref(defn.Predef_undefined)
   }
 }
 
@@ -622,6 +644,8 @@ class Inliner(call: tpd.Tree, rhsToInline: tpd.Tree)(using Context) {
         arg match
           case ConstantValue(_) | Inlined(_, Nil, Typed(ConstantValue(_), _)) => // ok
           case _ => report.error(em"expected a constant value but found: $arg", arg.srcPos)
+      case (strCtx :: Nil) :: (args :: Nil) :: Nil if inlinedMethod == defn.Compiletime_code =>
+        return Intrinsics.code(strCtx, args, call.srcPos)
       case _ =>
 
   	// Special handling of `constValue[T]` and `constValueOpt[T]`

library/src-bootstrapped/dotty/internal/CompileTimeMacros.scala

@@ -35,7 +35,7 @@ package object compiletime {
    /** Returns the string representation of interpolated elaborated code:
     *
     *  ```scala
-    *  inline def logged(p1: => Any) = {
+    *  inline def logged(inline p1: Any) = {
     *    val c = code"code: $p1"
     *    val res = p1
     *    (c, p1)
@@ -45,11 +45,13 @@ package object compiletime {
     *  // ("code: scala.Predef.identity("foo")", identity("foo"))
     *  ```
     *
-    * @note only by-name arguments will be displayed as "code".
+    *  The formatting of the code is not stable across version of the compiler.
+    *
+    * @note only `inline` arguments will be displayed as "code".
     *       Other values may display unintutively.
     */
-    transparent inline def code (inline args: Any*): String =
-      ${ dotty.internal.CompileTimeMacros.codeExpr('self, 'args) }
+    transparent inline def code (inline args: Any*): String = ???
+
   end extension
 
   /** Checks at compiletime that the provided values is a constant after

library/src-non-bootstrapped/dotty/internal/CompileTimeMacros.scala

@@ -1,6 +1,6 @@
-compile-time: (4: scala.Int)
+compile-time: 4:Int
 run-time: 4
-compile-time: (1: scala.Int)
+compile-time: 1:Int
 run-time: 1
 run-time: 5
 run-time: 7

library/src/scala/compiletime/package.scala

@@ -0,0 +1,6 @@
+abc println(34) ...
+abc println(34)
+println(34) ...
+println(34)
+...
+

tests/run-macros/beta-reduce-inline-result.check

@@ -3,12 +3,12 @@ import scala.compiletime._
 object Test {
 
   def main(args: Array[String]): Unit = {
-    assert(code"abc ${println(34)} ..." == "abc scala.Predef.println(34) ...")
-    assert(code"abc ${println(34)}" == "abc scala.Predef.println(34)")
-    assert(code"${println(34)} ..." == "scala.Predef.println(34) ...")
-    assert(code"${println(34)}" == "scala.Predef.println(34)")
-    assert(code"..." == "...")
-    assert(testConstant(code"") == "")
+    println(code"abc ${println(34)} ...")
+    println(code"abc ${println(34)}")
+    println(code"${println(34)} ...")
+    println(code"${println(34)}")
+    println(code"...")
+    println(testConstant(code""))
   }
 
   inline def testConstant(inline msg: String): String = msg