Rename InlineCopier to ConservativeTreeCopier, use it in TypeMaps (scala#21941)

Another attempt to fix scala#17242.

Previous attempts: scala#17256 and scala#21884.

Author: mbovel

compiler/src/dotty/tools/dotc/ast/tpd.scala

@@ -827,6 +827,14 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
       Closure(tree: Tree)(env, meth, tpt)
   }
 
+  // This is a more fault-tolerant copier that does not cause errors when
+  // function types in applications are undefined.
+  // This was called `Inliner.InlineCopier` before 3.6.3.
+  class ConservativeTreeCopier() extends TypedTreeCopier:
+    override def Apply(tree: Tree)(fun: Tree, args: List[Tree])(using Context): Apply =
+      if fun.tpe.widen.exists then super.Apply(tree)(fun, args)
+      else untpd.cpy.Apply(tree)(fun, args).withTypeUnchecked(tree.tpe)
+
   override def skipTransform(tree: Tree)(using Context): Boolean = tree.tpe.isError
 
   implicit class TreeOps[ThisTree <: tpd.Tree](private val tree: ThisTree) extends AnyVal {

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

@@ -6291,7 +6291,14 @@ object Types extends TypeUtils {
       }
     }
 
-    private def treeTypeMap = new TreeTypeMap(typeMap = this)
+    private def treeTypeMap = new TreeTypeMap(
+      typeMap = this,
+      // Using `ConservativeTreeCopier` is needed when copying dependent annoted
+      // types, where we can refer to a previous parameter represented as
+      // `TermParamRef` that has no underlying type yet.
+      // See tests/pos/annot-17242.scala.
+      cpy = ConservativeTreeCopier()
+    )
 
     def mapOver(syms: List[Symbol]): List[Symbol] = mapSymbols(syms, treeTypeMap)
 

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

@@ -96,15 +96,6 @@ object Inliner:
     }
   end isElideableExpr
 
-  // InlineCopier is a more fault-tolerant copier that does not cause errors when
-  // function types in applications are undefined. This is necessary since we copy at
-  // the same time as establishing the proper context in which the copied tree should
-  // be evaluated. This matters for opaque types, see neg/i14653.scala.
-  private class InlineCopier() extends TypedTreeCopier:
-    override def Apply(tree: Tree)(fun: Tree, args: List[Tree])(using Context): Apply =
-      if fun.tpe.widen.exists then super.Apply(tree)(fun, args)
-      else untpd.cpy.Apply(tree)(fun, args).withTypeUnchecked(tree.tpe)
-
   // InlinerMap is a TreeTypeMap with special treatment for inlined arguments:
   // They are generally left alone (not mapped further, and if they wrap a type
   // the type Inlined wrapper gets dropped
@@ -116,7 +107,13 @@ object Inliner:
       substFrom: List[Symbol],
       substTo: List[Symbol])(using Context)
     extends TreeTypeMap(
-      typeMap, treeMap, oldOwners, newOwners, substFrom, substTo, InlineCopier()):
+      typeMap, treeMap, oldOwners, newOwners, substFrom, substTo,
+      // It is necessary to use the `ConservativeTreeCopier` since we copy at
+      // the same time as establishing the proper context in which the copied
+      // tree should be evaluated. This matters for opaque types, see
+      // neg/i14653.scala.
+      ConservativeTreeCopier()
+    ):
 
     override def copy(
         typeMap: Type => Type,

tests/pos/annot-17242.scala

@@ -0,0 +1,5 @@
+// See also tests/pos/annot-21595.scala
+
+class local(predicate: Int) extends annotation.StaticAnnotation
+
+def failing1(x: Int, z: Int @local(x + x)) = ()

tests/pos/dependent-annot2.scala

@@ -0,0 +1,30 @@
+class dummy(b: Any) extends annotation.StaticAnnotation
+
+class X:
+  def foo() = 1
+  def bar() = 2
+  def eq(x: X) = true
+  def id(): this.type = this
+
+class Y extends X:
+  override def bar() = 2
+  override def eq(x: X) = true
+
+def f(x: Int) = x
+def g(x: String) = x
+def g(x: Int) = x
+
+object AnnotationTests:
+  def foo1(elem: Int, bla: Int @dummy(Array(elem))) = bla
+  def foo2(elem: X, bla: Int @dummy(elem.foo())) = bla
+  def foo3(elem: Y, bla: Int @dummy(elem.foo())) = bla
+  def foo4(elem: X, bla: Int @dummy(elem.bar())) = bla
+  def foo5(elem: Y, bla: Int @dummy(elem.bar())) = bla
+  def foo6(elem: X, bla: Int @dummy(elem.eq(X()))) = bla
+  def foo7(elem: Y, bla: Int @dummy(elem.eq(Y()))) = bla
+  def foo8(elem: X, bla: Int @dummy(elem.id().foo())) = bla
+  def foo9(elem: Y, bla: Int @dummy(elem.id().foo())) = bla
+  def foo10(elem: Int, bla: Int @dummy(f(elem))) = bla
+  def foo11(elem: Int, bla: Int @dummy(g(elem))) = bla
+  def foo12(elem: Int, bla: Int @dummy(0 == elem)) = bla
+  def foo13(elem: Int, bla: Int @dummy(elem == 0)) = bla