Implement -Yno-predef and -Yno-imports

src/dotty/tools/dotc/config/ScalaSettings.scala

@@ -128,7 +128,7 @@ class ScalaSettings extends Settings.SettingGroup {
   val Ylogcp = BooleanSetting("-Ylog-classpath", "Output information about what classpath is being applied.")
   val Ynogenericsig = BooleanSetting("-Yno-generic-signatures", "Suppress generation of generic signatures for Java.")
   val YnoImports = BooleanSetting("-Yno-imports", "Compile without importing scala.*, java.lang.*, or Predef.")
-  val nopredef = BooleanSetting("-Yno-predef", "Compile without importing Predef.")
+  val YnoPredef = BooleanSetting("-Yno-predef", "Compile without importing Predef.")
   val noAdaptedArgs = BooleanSetting("-Yno-adapted-args", "Do not adapt an argument list (either by inserting () or creating a tuple) to match the receiver.")
   val selfInAnnots = BooleanSetting("-Yself-in-annots", "Include a \"self\" identifier inside of annotations.")
   val Yshowtrees = BooleanSetting("-Yshow-trees", "(Requires -Xprint:) Print detailed ASTs in formatted form.")

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

@@ -627,15 +627,24 @@ class Definitions {
   def isTupleClass(cls: Symbol) = isVarArityClass(cls, tpnme.Tuple)
   def isProductClass(cls: Symbol) = isVarArityClass(cls, tpnme.Product)
 
-  val RootImportFns = List[() => TermRef](
-      () => JavaLangPackageVal.termRef,
-      () => ScalaPackageVal.termRef,
+  val StaticRootImportFns = List[() => TermRef](
+    () => JavaLangPackageVal.termRef,
+    () => ScalaPackageVal.termRef
+  )
+
+  val PredefImportFns = List[() => TermRef](
       () => ScalaPredefModuleRef,
-      () => DottyPredefModuleRef)
+      () => DottyPredefModuleRef
+  )
+
+  lazy val RootImportFns =
+    if (ctx.settings.YnoImports.value) List.empty[() => TermRef]
+    else if (ctx.settings.YnoPredef.value) StaticRootImportFns
+    else StaticRootImportFns ++ PredefImportFns
 
   lazy val RootImportTypes = RootImportFns.map(_())
 
-  /** `Modules whose members are in the default namespace and their module classes */
+  /** Modules whose members are in the default namespace and their module classes */
   lazy val UnqualifiedOwnerTypes: Set[NamedType] =
     RootImportTypes.toSet[NamedType] ++ RootImportTypes.map(_.symbol.moduleClass.typeRef)
 

test/dotc/tests.scala

@@ -136,6 +136,10 @@ class tests extends CompilerTest {
   @Test def neg_tailcall2 = compileFile(negTailcallDir, "tailrec-2")
   @Test def neg_tailcall3 = compileFile(negTailcallDir, "tailrec-3")
 
+  @Test def neg_nopredef = compileFile(negCustomArgs, "nopredef", List("-Yno-predef"))
+  @Test def neg_noimports = compileFile(negCustomArgs, "noimports", List("-Yno-imports"))
+  @Test def neg_noimpots2 = compileFile(negCustomArgs, "noimports2", List("-Yno-imports"))
+
   @Test def run_all = runFiles(runDir)
 
   val stdlibFiles = Source.fromFile("./test/dotc/scala-collections.whitelist", "UTF8").getLines()

tests/neg/customArgs/noimports.scala

@@ -0,0 +1,3 @@
+object Test {
+  val t: Int = 1 // error: not found Int
+}

tests/neg/customArgs/noimports2.scala

@@ -0,0 +1,3 @@
+object Test {
+  assert("asdf" == "asdf") // error: not found assert
+}

tests/neg/customArgs/nopredef.scala

@@ -0,0 +1,3 @@
+object Test {
+  assert("asdf" == "asdf") // error: not found assert
+}