Use tree checker in macros (#16570)

Trees are only checked if `-Xcheck-macros` is enabled.

Fixes:
 - Add missing positions to `{ValDef,Bind}.apply`
 - Inline by-name ascribed param
 - Unbound type variables after implicit search
 - Fixes #15779
 - Fixes #16636

Author: smarter

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

@@ -227,7 +227,7 @@ class Inliner(val call: tpd.Tree)(using Context):
     val binding = {
       var newArg = arg.changeOwner(ctx.owner, boundSym)
       if bindingFlags.is(Inline) && argIsBottom then
-        newArg = Typed(newArg, TypeTree(formal)) // type ascribe RHS to avoid type errors in expansion. See i8612.scala
+        newArg = Typed(newArg, TypeTree(formal.widenExpr)) // type ascribe RHS to avoid type errors in expansion. See i8612.scala
       if isByName then DefDef(boundSym, newArg)
       else ValDef(boundSym, newArg)
     }.withSpan(boundSym.span)
@@ -816,6 +816,7 @@ class Inliner(val call: tpd.Tree)(using Context):
                         && StagingContext.level == 0
                         && !hasInliningErrors =>
           val expanded = expandMacro(res.args.head, tree.srcPos)
+          transform.TreeChecker.checkMacroGeneratedTree(res, expanded)
           typedExpr(expanded) // Inline calls and constant fold code generated by the macro
         case res =>
           specializeEq(inlineIfNeeded(res, pt, locked))

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

@@ -82,8 +82,9 @@ class MacroAnnotations:
             case (prefixed, newTree :: suffixed) =>
               allTrees ++= prefixed
               insertedAfter = suffixed :: insertedAfter
-              prefixed.foreach(checkMacroDef(_, tree.symbol, annot))
-              suffixed.foreach(checkMacroDef(_, tree.symbol, annot))
+              prefixed.foreach(checkMacroDef(_, tree, annot))
+              suffixed.foreach(checkMacroDef(_, tree, annot))
+              transform.TreeChecker.checkMacroGeneratedTree(tree, newTree)
               newTree
             case (Nil, Nil) =>
               report.error(i"Unexpected `Nil` returned by `(${annot.tree}).transform(..)` during macro expansion", annot.tree.srcPos)
@@ -119,8 +120,10 @@ class MacroAnnotations:
     annotInstance.transform(using quotes)(tree.asInstanceOf[quotes.reflect.Definition])
 
   /** Check that this tree can be added by the macro annotation */
-  private def checkMacroDef(newTree: DefTree, annotated: Symbol, annot: Annotation)(using Context) =
+  private def checkMacroDef(newTree: DefTree, annotatedTree: Tree, annot: Annotation)(using Context) =
+    transform.TreeChecker.checkMacroGeneratedTree(annotatedTree, newTree)
     val sym = newTree.symbol
+    val annotated = annotatedTree.symbol
     if sym.isType && !sym.isClass then
       report.error(i"macro annotation cannot return a `type`. $annot tried to add $sym", annot.tree)
     else if sym.owner != annotated.owner && !(annotated.owner.isPackageObject && (sym.isClass || sym.is(Module)) && sym.owner == annotated.owner.owner) then

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

@@ -42,10 +42,6 @@ class TreeChecker extends Phase with SymTransformer {
   private val seenClasses = collection.mutable.HashMap[String, Symbol]()
   private val seenModuleVals = collection.mutable.HashMap[String, Symbol]()
 
-  def isValidJVMName(name: Name): Boolean = name.toString.forall(isValidJVMChar)
-
-  def isValidJVMMethodName(name: Name): Boolean = name.toString.forall(isValidJVMMethodChar)
-
   val NoSuperClassFlags: FlagSet = Trait | Package
 
   def testDuplicate(sym: Symbol, registry: mutable.Map[String, Symbol], typ: String)(using Context): Unit = {
@@ -109,18 +105,6 @@ class TreeChecker extends Phase with SymTransformer {
     else if (ctx.phase.prev.isCheckable)
       check(ctx.base.allPhases.toIndexedSeq, ctx)
 
-  private def previousPhases(phases: List[Phase])(using Context): List[Phase] = phases match {
-    case (phase: MegaPhase) :: phases1 =>
-      val subPhases = phase.miniPhases
-      val previousSubPhases = previousPhases(subPhases.toList)
-      if (previousSubPhases.length == subPhases.length) previousSubPhases ::: previousPhases(phases1)
-      else previousSubPhases
-    case phase :: phases1 if phase ne ctx.phase =>
-      phase :: previousPhases(phases1)
-    case _ =>
-      Nil
-  }
-
   def check(phasesToRun: Seq[Phase], ctx: Context): Tree = {
     val fusedPhase = ctx.phase.prevMega(using ctx)
     report.echo(s"checking ${ctx.compilationUnit} after phase ${fusedPhase}")(using ctx)
@@ -134,7 +118,6 @@ class TreeChecker extends Phase with SymTransformer {
 
     val checkingCtx = ctx
         .fresh
-        .addMode(Mode.ImplicitsEnabled)
         .setReporter(new ThrowingReporter(ctx.reporter))
 
     val checker = inContext(ctx) {
@@ -150,9 +133,80 @@ class TreeChecker extends Phase with SymTransformer {
     }
   }
 
+  /**
+    * Checks that `New` nodes are always wrapped inside `Select` nodes.
+    */
+  def assertSelectWrapsNew(tree: Tree)(using Context): Unit =
+    (new TreeAccumulator[tpd.Tree] {
+      override def apply(parent: Tree, tree: Tree)(using Context): Tree = {
+        tree match {
+          case tree: New if !parent.isInstanceOf[tpd.Select] =>
+            assert(assertion = false, i"`New` node must be wrapped in a `Select`:\n  parent = ${parent.show}\n  child = ${tree.show}")
+          case _: Annotated =>
+            // Don't check inside annotations, since they're allowed to contain
+            // somewhat invalid trees.
+          case _ =>
+            foldOver(tree, tree) // replace the parent when folding over the children
+        }
+        parent // return the old parent so that my siblings see it
+      }
+    })(tpd.EmptyTree, tree)
+}
+
+object TreeChecker {
+  /** - Check that TypeParamRefs and MethodParams refer to an enclosing type.
+   *  - Check that all type variables are instantiated.
+   */
+  def checkNoOrphans(tp0: Type, tree: untpd.Tree = untpd.EmptyTree)(using Context): Type = new TypeMap() {
+    val definedBinders = new java.util.IdentityHashMap[Type, Any]
+    def apply(tp: Type): Type = {
+      tp match {
+        case tp: BindingType =>
+          definedBinders.put(tp, tp)
+          mapOver(tp)
+          definedBinders.remove(tp)
+        case tp: ParamRef =>
+          assert(definedBinders.get(tp.binder) != null, s"orphan param: ${tp.show}, hash of binder = ${System.identityHashCode(tp.binder)}, tree = ${tree.show}, type = $tp0")
+        case tp: TypeVar =>
+          assert(tp.isInstantiated, s"Uninstantiated type variable: ${tp.show}, tree = ${tree.show}")
+          apply(tp.underlying)
+        case _ =>
+          mapOver(tp)
+      }
+      tp
+    }
+  }.apply(tp0)
+
+  /** Run some additional checks on the nodes of the trees.  Specifically:
+   *
+   *    - TypeTree can only appear in TypeApply args, New, Typed tpt, Closure
+   *      tpt, SeqLiteral elemtpt, ValDef tpt, DefDef tpt, and TypeDef rhs.
+   */
+  object TreeNodeChecker extends untpd.TreeTraverser:
+    import untpd._
+    def traverse(tree: Tree)(using Context) = tree match
+      case t: TypeTree                             => assert(assertion = false, i"TypeTree not expected: $t")
+      case t @ TypeApply(fun, _targs)              => traverse(fun)
+      case t @ New(_tpt)                           =>
+      case t @ Typed(expr, _tpt)                   => traverse(expr)
+      case t @ Closure(env, meth, _tpt)            => traverse(env); traverse(meth)
+      case t @ SeqLiteral(elems, _elemtpt)         => traverse(elems)
+      case t @ ValDef(_, _tpt, _)                  => traverse(t.rhs)
+      case t @ DefDef(_, paramss, _tpt, _)         => for params <- paramss do traverse(params); traverse(t.rhs)
+      case t @ TypeDef(_, _rhs)                    =>
+      case t @ Template(constr, parents, self, _)  => traverse(constr); traverse(parents); traverse(self); traverse(t.body)
+      case t                                       => traverseChildren(t)
+    end traverse
+
+  private[TreeChecker] def isValidJVMName(name: Name): Boolean = name.toString.forall(isValidJVMChar)
+
+  private[TreeChecker] def isValidJVMMethodName(name: Name): Boolean = name.toString.forall(isValidJVMMethodChar)
+
+
   class Checker(phasesToCheck: Seq[Phase]) extends ReTyper with Checking {
+    import ast.tpd._
 
-    private val nowDefinedSyms = util.HashSet[Symbol]()
+    protected val nowDefinedSyms = util.HashSet[Symbol]()
     private val patBoundSyms = util.HashSet[Symbol]()
     private val everDefinedSyms = MutableSymbolMap[untpd.Tree]()
 
@@ -658,68 +712,50 @@ class TreeChecker extends Phase with SymTransformer {
     override def simplify(tree: Tree, pt: Type, locked: TypeVars)(using Context): tree.type = tree
   }
 
-  /**
-    * Checks that `New` nodes are always wrapped inside `Select` nodes.
-    */
-  def assertSelectWrapsNew(tree: Tree)(using Context): Unit =
-    (new TreeAccumulator[tpd.Tree] {
-      override def apply(parent: Tree, tree: Tree)(using Context): Tree = {
-        tree match {
-          case tree: New if !parent.isInstanceOf[tpd.Select] =>
-            assert(assertion = false, i"`New` node must be wrapped in a `Select`:\n  parent = ${parent.show}\n  child = ${tree.show}")
-          case _: Annotated =>
-            // Don't check inside annotations, since they're allowed to contain
-            // somewhat invalid trees.
-          case _ =>
-            foldOver(tree, tree) // replace the parent when folding over the children
-        }
-        parent // return the old parent so that my siblings see it
-      }
-    })(tpd.EmptyTree, tree)
-}
+  /** Tree checker that can be applied to a local tree. */
+  class LocalChecker(phasesToCheck: Seq[Phase]) extends Checker(phasesToCheck: Seq[Phase]):
+    override def assertDefined(tree: untpd.Tree)(using Context): Unit =
+      // Only check definitions nested in the local tree
+      if nowDefinedSyms.contains(tree.symbol.maybeOwner) then
+        super.assertDefined(tree)
 
-object TreeChecker {
-  /** - Check that TypeParamRefs and MethodParams refer to an enclosing type.
-   *  - Check that all type variables are instantiated.
-   */
-  def checkNoOrphans(tp0: Type, tree: untpd.Tree = untpd.EmptyTree)(using Context): Type = new TypeMap() {
-    val definedBinders = new java.util.IdentityHashMap[Type, Any]
-    def apply(tp: Type): Type = {
-      tp match {
-        case tp: BindingType =>
-          definedBinders.put(tp, tp)
-          mapOver(tp)
-          definedBinders.remove(tp)
-        case tp: ParamRef =>
-          assert(definedBinders.get(tp.binder) != null, s"orphan param: ${tp.show}, hash of binder = ${System.identityHashCode(tp.binder)}, tree = ${tree.show}, type = $tp0")
-        case tp: TypeVar =>
-          assert(tp.isInstantiated, s"Uninstantiated type variable: ${tp.show}, tree = ${tree.show}")
-          apply(tp.underlying)
-        case _ =>
-          mapOver(tp)
-      }
-      tp
-    }
-  }.apply(tp0)
+  def checkMacroGeneratedTree(original: tpd.Tree, expansion: tpd.Tree)(using Context): Unit =
+    if ctx.settings.XcheckMacros.value then
+      val checkingCtx = ctx
+        .fresh
+        .setReporter(new ThrowingReporter(ctx.reporter))
+      val phases = ctx.base.allPhases.toList
+      val treeChecker = new LocalChecker(previousPhases(phases))
+
+      try treeChecker.typed(expansion)(using checkingCtx)
+      catch
+        case err: java.lang.AssertionError =>
+          report.error(
+            s"""Malformed tree was found while expanding macro with -Xcheck-macros.
+               |The tree does not conform to the compiler's tree invariants.
+               |
+               |Macro was:
+               |${scala.quoted.runtime.impl.QuotesImpl.showDecompiledTree(original)}
+               |
+               |The macro returned:
+               |${scala.quoted.runtime.impl.QuotesImpl.showDecompiledTree(expansion)}
+               |
+               |Error:
+               |${err.getMessage}
+               |
+               |""",
+            original
+          )
 
-  /** Run some additional checks on the nodes of the trees.  Specifically:
-   *
-   *    - TypeTree can only appear in TypeApply args, New, Typed tpt, Closure
-   *      tpt, SeqLiteral elemtpt, ValDef tpt, DefDef tpt, and TypeDef rhs.
-   */
-  object TreeNodeChecker extends untpd.TreeTraverser:
-    import untpd._
-    def traverse(tree: Tree)(using Context) = tree match
-      case t: TypeTree                             => assert(assertion = false, i"TypeTree not expected: $t")
-      case t @ TypeApply(fun, _targs)              => traverse(fun)
-      case t @ New(_tpt)                           =>
-      case t @ Typed(expr, _tpt)                   => traverse(expr)
-      case t @ Closure(env, meth, _tpt)            => traverse(env); traverse(meth)
-      case t @ SeqLiteral(elems, _elemtpt)         => traverse(elems)
-      case t @ ValDef(_, _tpt, _)                  => traverse(t.rhs)
-      case t @ DefDef(_, paramss, _tpt, _)         => for params <- paramss do traverse(params); traverse(t.rhs)
-      case t @ TypeDef(_, _rhs)                    =>
-      case t @ Template(constr, parents, self, _)  => traverse(constr); traverse(parents); traverse(self); traverse(t.body)
-      case t                                       => traverseChildren(t)
-    end traverse
+  private[TreeChecker] def previousPhases(phases: List[Phase])(using Context): List[Phase] = phases match {
+    case (phase: MegaPhase) :: phases1 =>
+      val subPhases = phase.miniPhases
+      val previousSubPhases = previousPhases(subPhases.toList)
+      if (previousSubPhases.length == subPhases.length) previousSubPhases ::: previousPhases(phases1)
+      else previousSubPhases
+    case phase :: phases1 if phase ne ctx.phase =>
+      phase :: previousPhases(phases1)
+    case _ =>
+      Nil
+  }
 }

compiler/src/scala/quoted/runtime/impl/QuotesImpl.scala

@@ -307,7 +307,7 @@ class QuotesImpl private (using val ctx: Context) extends Quotes, QuoteUnpickler
 
     object ValDef extends ValDefModule:
       def apply(symbol: Symbol, rhs: Option[Term]): ValDef =
-        tpd.ValDef(symbol.asTerm, xCheckMacroedOwners(xCheckMacroValidExpr(rhs), symbol).getOrElse(tpd.EmptyTree))
+        withDefaultPos(tpd.ValDef(symbol.asTerm, xCheckMacroedOwners(xCheckMacroValidExpr(rhs), symbol).getOrElse(tpd.EmptyTree)))
       def copy(original: Tree)(name: String, tpt: TypeTree, rhs: Option[Term]): ValDef =
         tpd.cpy.ValDef(original)(name.toTermName, tpt, xCheckMacroedOwners(xCheckMacroValidExpr(rhs), original.symbol).getOrElse(tpd.EmptyTree))
       def unapply(vdef: ValDef): (String, TypeTree, Option[Term]) =
@@ -1483,7 +1483,7 @@ class QuotesImpl private (using val ctx: Context) extends Quotes, QuoteUnpickler
 
     object Bind extends BindModule:
       def apply(sym: Symbol, pattern: Tree): Bind =
-        tpd.Bind(sym, pattern)
+        withDefaultPos(tpd.Bind(sym, pattern))
       def copy(original: Tree)(name: String, pattern: Tree): Bind =
         withDefaultPos(tpd.cpy.Bind(original)(name.toTermName, pattern))
       def unapply(pattern: Bind): (String, Tree) =
@@ -2404,7 +2404,13 @@ class QuotesImpl private (using val ctx: Context) extends Quotes, QuoteUnpickler
 
     object Implicits extends ImplicitsModule:
       def search(tpe: TypeRepr): ImplicitSearchResult =
-        ctx.typer.inferImplicitArg(tpe, Position.ofMacroExpansion.span)
+        import tpd.TreeOps
+        val implicitTree = ctx.typer.inferImplicitArg(tpe, Position.ofMacroExpansion.span)
+        // Make sure that we do not have any uninstantiated type variables.
+        // See tests/pos-macros/i16636.
+        // See tests/pos-macros/exprSummonWithTypeVar with -Xcheck-macros.
+        dotc.typer.Inferencing.fullyDefinedType(implicitTree.tpe, "", implicitTree)
+        implicitTree
     end Implicits
 
     type ImplicitSearchResult = Tree

tests/neg-macros/annot-mod-top-method-add-top-method/Macro_1.scala

@@ -9,5 +9,5 @@ class addTopLevelMethodOutsidePackageObject extends MacroAnnotation:
     import quotes.reflect._
     val methType = MethodType(Nil)(_ => Nil, _ => TypeRepr.of[Int])
     val methSym = Symbol.newMethod(Symbol.spliceOwner.owner, Symbol.freshName("toLevelMethod"), methType, Flags.EmptyFlags, Symbol.noSymbol)
-    val methDef = ValDef(methSym, Some(Literal(IntConstant(1))))
+    val methDef = DefDef(methSym, _ => Some(Literal(IntConstant(1))))
     List(methDef, tree)

tests/pos-macros/exprSummonWithTypeVar/Macro_1.scala

@@ -0,0 +1,13 @@
+import scala.compiletime.{erasedValue, summonFrom}
+
+import scala.quoted._
+
+inline given summonAfterTypeMatch[T]: Any =
+  ${ summonAfterTypeMatchExpr[T] }
+
+private def summonAfterTypeMatchExpr[T: Type](using Quotes): Expr[Any] =
+  Expr.summon[Foo[T]].get
+
+trait Foo[T]
+
+given IntFoo[T <: Int]: Foo[T] = ???

tests/pos-macros/exprSummonWithTypeVar/Test_2.scala

@@ -0,0 +1 @@
+def test: Unit = summonAfterTypeMatch[Int]

tests/pos-macros/i15779/Macro_1.scala

@@ -0,0 +1,30 @@
+import scala.quoted._
+import scala.deriving.Mirror
+
+trait Encoder[-A]
+
+trait PrimitiveEncoder[A] extends Encoder[A]
+
+given intOpt: PrimitiveEncoder[Option[Int]] with {}
+
+given primitiveNotNull[T](using e: Encoder[Option[T]]): PrimitiveEncoder[T] =
+  new PrimitiveEncoder[T] {}
+
+transparent inline given fromMirror[A]: Any = ${ fromMirrorImpl[A] }
+
+def fromMirrorImpl[A : Type](using q: Quotes): Expr[Any] =
+  Expr.summon[Mirror.Of[A]].get match
+    case '{ ${mirror}: Mirror.ProductOf[A] { type MirroredElemTypes = elementTypes } } =>
+      val encoder = Type.of[elementTypes] match
+        case '[tpe *: EmptyTuple] =>
+          Expr.summon[Encoder[tpe]].get
+
+      encoder match
+        case '{ ${encoder}: Encoder[tpe] } => // ok
+        case _ => ???
+
+      encoder match
+        case '{ ${encoder}: Encoder[tpe] } => // ok
+        case _ => ???
+
+      encoder

tests/pos-macros/i15779/Test_2.scala

@@ -0,0 +1,3 @@
+case class JustInt(i: Int)
+
+val x = fromMirror[JustInt]

tests/pos-macros/i16636/Macro_1.scala

@@ -0,0 +1,30 @@
+import scala.quoted.*
+
+trait ReproTransformer[A, B] {
+  def transform(from: A): B
+}
+
+object ReproTransformer {
+  final class Identity[A, B >: A] extends ReproTransformer[A, B] {
+    def transform(from: A): B = from
+  }
+
+  given identity[A, B >: A]: Identity[A, B] = Identity[A, B]
+
+  inline def getTransformer[A, B]: ReproTransformer[A, B] = ${ getTransformerMacro[A, B] }
+
+  def getTransformerMacro[A, B](using quotes: Quotes, A: Type[A], B: Type[B]) = {
+    import quotes.reflect.*
+
+    val transformer = (A -> B) match {
+      case '[a] -> '[b] =>
+        val summoned = Expr.summon[ReproTransformer[a, b]].get
+// ----------- INTERESTING STUFF STARTS HERE
+        summoned match {
+          case '{ $t: ReproTransformer[src, dest] } => t
+        }
+// ----------- INTERESTING STUFF ENDS HERE
+    }
+    transformer.asExprOf[ReproTransformer[A, B]]
+  }
+}