Check New tree for ill-formed module instantiations (#17553)

Fixes #17545

Author: nicolasstucki

compiler/src/dotty/tools/dotc/transform/TreeChecker.scala

@@ -495,6 +495,18 @@ object TreeChecker {
       assert(tree.qual.typeOpt.isInstanceOf[ThisType], i"expect prefix of Super to be This, actual = ${tree.qual}")
       super.typedSuper(tree, pt)
 
+    override def typedNew(tree: untpd.New, pt: Type)(using Context): Tree =
+      val tree1 = super.typedNew(tree, pt).asInstanceOf[tpd.New]
+      val sym = tree1.tpe.typeSymbol
+      if postTyperPhase <= ctx.phase then // postTyper checks that `New` nodes can be instantiated
+        assert(!tree1.tpe.isInstanceOf[TermRef], s"New should not have a TermRef type: ${tree1.tpe}")
+        assert(
+          !sym.is(Module)
+          || ctx.erasedTypes // TODO add check for module initialization after erasure (LazyVals transformation)
+          || ctx.owner == sym.companionModule,
+          i"new of $sym module should only exist in ${sym.companionModule} but was in ${ctx.owner}")
+      tree1
+
     override def typedApply(tree: untpd.Apply, pt: Type)(using Context): Tree = tree match
       case Apply(Select(qual, nme.CONSTRUCTOR), _)
           if !ctx.phase.erasedTypes

tests/neg-macros/i17545a/Macro_1.scala

@@ -0,0 +1,11 @@
+import scala.quoted.*
+
+object InvokeConstructor {
+  inline def apply[A] = ${ constructorMacro[A] }
+
+  def constructorMacro[A: Type](using Quotes) = {
+    import quotes.reflect.*
+    val tpe = TypeRepr.of[A]
+    New(Inferred(tpe)).select(tpe.typeSymbol.primaryConstructor).appliedToArgs(Nil).asExprOf[A]
+  }
+}

tests/neg-macros/i17545a/Test_2.scala

@@ -0,0 +1,4 @@
+case object WhateverA
+
+def testA =
+  val whateverA: WhateverA.type = InvokeConstructor[WhateverA.type] // error

tests/neg-macros/i17545b/Macro_1.scala

@@ -0,0 +1,11 @@
+import scala.quoted.*
+
+object InvokeConstructor {
+  inline def apply[A] = ${ constructorMacro[A] }
+
+  def constructorMacro[A: Type](using Quotes) = {
+    import quotes.reflect.*
+    val tpe = TypeRepr.of[A]
+    New(Inferred(tpe)).select(tpe.typeSymbol.primaryConstructor).appliedToArgs(Nil).asExprOf[A]
+  }
+}

tests/neg-macros/i17545b/Test_2.scala

@@ -0,0 +1,3 @@
+def testB =
+  case object WhateverB
+  val whateverB: WhateverB.type = InvokeConstructor[WhateverB.type] // error

tests/neg-macros/i17545c/Macro_1.scala

@@ -0,0 +1,11 @@
+import scala.quoted.*
+
+object InvokeConstructor {
+  inline def apply[A] = ${ constructorMacro[A] }
+
+  def constructorMacro[A: Type](using Quotes) = {
+    import quotes.reflect.*
+    val tpe = TypeRepr.of[A].termSymbol.moduleClass.typeRef
+    New(Inferred(tpe)).select(tpe.typeSymbol.primaryConstructor).appliedToArgs(Nil).asExprOf[A]
+  }
+}

tests/neg-macros/i17545c/Test_2.scala

@@ -0,0 +1,4 @@
+case object WhateverA
+
+def testA =
+  val whateverA: WhateverA.type = InvokeConstructor[WhateverA.type] // error

tests/neg-macros/i17545d/Macro_1.scala

@@ -0,0 +1,11 @@
+import scala.quoted.*
+
+object InvokeConstructor {
+  inline def apply[A] = ${ constructorMacro[A] }
+
+  def constructorMacro[A: Type](using Quotes) = {
+    import quotes.reflect.*
+    val tpe = TypeRepr.of[A].termSymbol.moduleClass.typeRef
+    New(Inferred(tpe)).select(tpe.typeSymbol.primaryConstructor).appliedToArgs(Nil).asExprOf[A]
+  }
+}

tests/neg-macros/i17545d/Test_2.scala

@@ -0,0 +1,3 @@
+def testB =
+  case object WhateverB
+  val whateverB: WhateverB.type = InvokeConstructor[WhateverB.type] // error