No longer eagerly evaluate calleeType/calleeIsErased

Author: natsukagami

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

@@ -1444,7 +1444,7 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
         NoType
     }
 
-    val calleeIsErased = calleeType.widen match {
+    lazy val calleeIsErased = calleeType.widen match {
       case mt: MethodType if mt.isErasedMethod =>
         val companion = mt.companion.asInstanceOf[ErasedMethodCompanion]
         params.map(p => companion.isErased(paramIndex(p.name)))
@@ -1466,7 +1466,7 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
 
     /** Returns the type and whether the parameter is erased */
     def protoFormal(i: Int): (Type, Boolean) =
-      if (protoFormals.length == params.length) (protoFormals(i), calleeIsErased(i) || isDefinedErased(i))
+      if (protoFormals.length == params.length) (protoFormals(i), isDefinedErased(i))
       else (errorType(WrongNumberOfParameters(protoFormals.length), tree.srcPos), isDefinedErased(i))
 
     /** Is `formal` a product type which is elementwise compatible with `params`? */
@@ -1504,21 +1504,23 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
       val inferredParams: List[untpd.ValDef] =
         for ((param, i) <- params.zipWithIndex) yield
           val (formal, isErased) = protoFormal(i)
-          val param0 =
-            if (!param.tpt.isEmpty) param
+          val (param0, isErased1) =
+            if (!param.tpt.isEmpty) (param, false)
             else
               val knownFormal = isFullyDefined(formal, ForceDegree.failBottom)
-              val paramType =
-                if knownFormal then formal
-                else inferredFromTarget(param, formal, calleeType, paramIndex)
-                  .orElse(errorType(AnonymousFunctionMissingParamType(param, tree, formal), param.srcPos))
+              val (paramType, isErased1) =
+                if knownFormal then (formal, false)
+                else
+                  val tpe = inferredFromTarget(param, formal, calleeType, paramIndex)
+                    .orElse(errorType(AnonymousFunctionMissingParamType(param, tree, formal), param.srcPos))
+                  (tpe, calleeIsErased(i))
               val paramTpt = untpd.TypedSplice(
                   (if knownFormal then InferredTypeTree() else untpd.TypeTree())
                     .withType(paramType.translateFromRepeated(toArray = false))
                     .withSpan(param.span.endPos)
                 )
-              cpy.ValDef(param)(tpt = paramTpt)
-          if isErased then param0.withAddedFlags(Flags.Erased) else param0
+              (cpy.ValDef(param)(tpt = paramTpt), isErased1)
+          if isErased || isErased1 then param0.withAddedFlags(Flags.Erased) else param0
       desugared = desugar.makeClosure(inferredParams, fnBody, resultTpt, isContextual, tree.span)
 
     typed(desugared, pt)