Add isMethodWithByNameArgs

Author: nicolasstucki

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

@@ -1151,7 +1151,7 @@ class Definitions {
         case info: MethodType =>
           !info.resType.isInstanceOf[MethodOrPoly] && // Has only one parameter list
           !info.isVarArgsMethod &&
-          !info.paramInfos.exists(_.isInstanceOf[ExprType]) // No by-name parameters
+          !info.isMethodWithByNameArgs // No by-name parameters
         case _ => false
       info match
         case info: PolyType => isValidMethodType(info.resType)

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

@@ -429,6 +429,12 @@ object Types {
       case _ => false
     }
 
+    /** Is this the type of a method that has a by-name parameters? */
+    def isMethodWithByNameArgs(using Context): Boolean = stripPoly match {
+      case mt: MethodType => mt.paramInfos.exists(_.isInstanceOf[ExprType])
+      case _ => false
+    }
+
     /** Is this the type of a method with a leading empty parameter list?
      */
     def isNullaryMethod(using Context): Boolean = stripPoly match {

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

@@ -188,7 +188,7 @@ abstract class Recheck extends Phase, SymTransformer:
      *  of `mapExprType`.
      */
     def normalizeByName(mbr: SingleDenotation)(using Context): SingleDenotation = mbr.info match
-      case mt: MethodType if mt.paramInfos.exists(_.isInstanceOf[ExprType]) =>
+      case mt: MethodType if mt.isMethodWithByNameArgs =>
         mbr.derivedSingleDenotation(mbr.symbol,
           mt.derivedLambdaType(paramInfos = mt.paramInfos.map(_.mapExprType)))
       case _ =>

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

@@ -518,7 +518,7 @@ object Nullables:
   def postProcessByNameArgs(fn: TermRef, app: Tree)(using Context): Tree =
     fn.widen match
       case mt: MethodType
-      if mt.paramInfos.exists(_.isInstanceOf[ExprType]) && !fn.symbol.is(Inline) =>
+      if mt.isMethodWithByNameArgs && !fn.symbol.is(Inline) =>
         app match
           case Apply(fn, args) =>
             object dropNotNull extends TreeMap: