add PreTypedTypeTree to memoize type checked trees

Author: albertpchen

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

@@ -345,6 +345,12 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
     def derivedTree(originalSym: Symbol)(using Context): tpd.Tree
   }
 
+  /** A type tree that memoizes the result of a typed tree. Used when
+   *  typechecking selectDynamic calls to prevent typechecking type arguments
+   *  multiple types.
+   */
+  final class MemoizedTypeTree(val result: tpd.Tree)(implicit @constructorOnly src: SourceFile) extends TypeTree
+
   /** Property key containing TypeTrees whose type is computed
    *  from the symbol in this type. These type trees have marker trees
    *  TypeRefOfSym or InfoOfSym as their originals.

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

@@ -1076,7 +1076,7 @@ trait Applications extends Compatibility {
           case _ =>
         }
         def tryDynamicTypeApply(): Tree = typedFn match {
-          case typedFn: Select if !pt.isInstanceOf[FunProto] => typedDynamicSelect(typedFn, tree.args, pt)
+          case typedFn: Select if !pt.isInstanceOf[FunProto] => typedDynamicSelect(typedFn, typedArgs.map(untpd.MemoizedTypeTree(_)), pt)
           case _                                             => tree.withType(TryDynamicCallType)
         }
         if (typedFn.tpe eq TryDynamicCallType) tryDynamicTypeApply()

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

@@ -1695,6 +1695,7 @@ class Typer extends Namer
           case None =>
             errorTree(tree, "Something's wrong: missing original symbol for type tree")
         }
+      case tree: untpd.MemoizedTypeTree => tree.result
       case _ =>
         tree.withType(
           if (isFullyDefined(pt, ForceDegree.flipBottom)) pt