Intrinsify f interpolator

Author: nicolasstucki

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

@@ -631,10 +631,17 @@ class Definitions {
     def StringContextS(implicit ctx: Context): Symbol = StringContextSR.symbol
     lazy val StringContextRawR: TermRef = StringContextClass.requiredMethodRef(nme.raw_)
     def StringContextRaw(implicit ctx: Context): Symbol = StringContextRawR.symbol
+    lazy val StringContext_fR: TermRef = StringContextClass.requiredMethodRef(nme.f)
+    def StringContext_f(implicit ctx: Context): Symbol = StringContext_fR.symbol
   def StringContextModule(implicit ctx: Context): Symbol = StringContextClass.companionModule
     lazy val StringContextModule_applyR: TermRef = StringContextModule.requiredMethodRef(nme.apply)
     def StringContextModule_apply(implicit ctx: Context): Symbol = StringContextModule_applyR.symbol
 
+  lazy val InternalStringContextModuleR: TermRef = ctx.requiredModuleRef("scala.internal.StringContext")
+  def InternalStringContextModule(implicit ctx: Context): Symbol = InternalStringContextModuleR.termSymbol
+    lazy val InternalStringContextModule_fR: TermRef = InternalStringContextModule.requiredMethodRef(nme.f)
+    def InternalStringContextModule_f(implicit ctx: Context): Symbol = InternalStringContextModule_fR.symbol
+
   lazy val PartialFunctionType: TypeRef         = ctx.requiredClassRef("scala.PartialFunction")
   def PartialFunctionClass(implicit ctx: Context): ClassSymbol = PartialFunctionType.symbol.asClass
     lazy val PartialFunction_isDefinedAtR: TermRef = PartialFunctionClass.requiredMethodRef(nme.isDefinedAt)

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

@@ -2656,8 +2656,14 @@ class Typer extends Namer
         readaptSimplified(Inliner.inlineCall(tree, pt))
       }
       else if (tree.symbol.is(Macro, butNot = Inline)) {
-        ctx.error("Scala 2 macro cannot be used in Dotty. See http://dotty.epfl.ch/docs/reference/dropped-features/macros.html", tree.sourcePos)
-        tree
+        if (tree.symbol eq defn.StringContext_f) {
+          val Apply(TypeApply(Select(sc, _), _), args) = tree
+          val newCall = ref(defn.InternalStringContextModule_f).appliedTo(sc).appliedToArgs(args)
+          Inliner.inlineCall(newCall, pt)
+        } else {
+          ctx.error("Scala 2 macro cannot be used in Dotty. See http://dotty.epfl.ch/docs/reference/dropped-features/macros.html", tree.sourcePos)
+          tree
+        }
       }
       else if (tree.tpe <:< pt) {
         if (pt.hasAnnotation(defn.InlineParamAnnot))

library/src-bootstrapped/scala/internal/StringContext.scala

@@ -0,0 +1,15 @@
+package scala.internal
+
+import scala.quoted._
+
+object StringContext {
+
+  inline def f(sc: => scala.StringContext)(args: Any*): String = ${ fImpl('sc, 'args) }
+
+  private def fImpl(sc: Expr[StringContext], args: Expr[Seq[Any]]): Expr[String] = {
+    // TODO implement f interpolation checks and addapt sc.parts
+    //   See https://github.com/alemannosara/f-interpolators-in-Dotty-macros
+    '{ $sc.parts.mkString.format($args: _*) }
+  }
+
+}

library/src-non-bootstrapped/scala/internal/StringContext.scala

@@ -0,0 +1,8 @@
+package scala.internal
+
+object StringContext {
+
+  @forceInline def f(sc: => scala.StringContext)(args: Any*): String =
+    throw new Exception("non-boostrapped library")
+
+}

tests/run-with-compiler/f-interpolator.check

@@ -0,0 +1,2 @@
+abc
+Hello world

tests/run-with-compiler/f-interpolator.scala

@@ -0,0 +1,7 @@
+
+object Test {
+  def main(args: Array[String]): Unit = {
+    println(f"abc")
+    println(f"Hello ${"world"}%s")
+  }
+}