Add missing cases for flexible types in Quotes

Author: noti0na1

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

@@ -2230,7 +2230,7 @@ class QuotesImpl private (using val ctx: Context) extends Quotes, QuoteUnpickler
         def isErased: Boolean = false
         def isImplicit: Boolean = self.isImplicitMethod
         def isContextual: Boolean = self.isContextualMethod
-        def methodTypeKind: MethodTypeKind = 
+        def methodTypeKind: MethodTypeKind =
           self.companion match
             case Types.ContextualMethodType => MethodTypeKind.Contextual
             case Types.ImplicitMethodType => MethodTypeKind.Implicit
@@ -2343,6 +2343,21 @@ class QuotesImpl private (using val ctx: Context) extends Quotes, QuoteUnpickler
       def unapply(x: NoPrefix): true = true
     end NoPrefix
 
+    type FlexibleType = dotc.core.Types.FlexibleType
+
+    object FlexibleTypeTest extends TypeTest[TypeRepr, FlexibleType]:
+      def unapply(x: TypeRepr): Option[FlexibleType & x.type] = x match
+        case x: (Types.FlexibleType & x.type) => Some(x)
+        case _ => None
+    end FlexibleTypeTest
+
+    object FlexibleType extends FlexibleTypeModule:
+      def apply(tp: TypeRepr): FlexibleType =
+        // why object FlexibleType.apply(Type) is not found here?
+        Types.FlexibleType(tp, tp)
+      def unapply(x: FlexibleType): TypeRepr = x.hi
+    end FlexibleType
+
     type Constant = dotc.core.Constants.Constant
 
     object Constant extends ConstantModule

compiler/src/scala/quoted/runtime/impl/printers/Extractors.scala

@@ -239,6 +239,8 @@ object Extractors {
         this += "NoPrefix()"
       case MatchCase(pat, rhs) =>
         this += "MatchCase(" += pat += ", " += rhs += ")"
+      case FlexibleType(tp) =>
+        this += "FlexibleType(" += tp += ")"
     }
 
     def visitSignature(sig: Signature): this.type = {

compiler/src/scala/quoted/runtime/impl/printers/SourceCode.scala

@@ -1247,6 +1247,11 @@ object SourceCode {
         this += " => "
         printType(rhs)
 
+      case FlexibleType(tp) =>
+        this += "("
+        printType(tp)
+        this += ")?"
+
       case _ =>
         cannotBeShownAsSource(tpe.show(using Printer.TypeReprStructure))
     }

library/src/scala/quoted/Quotes.scala

@@ -211,7 +211,7 @@ trait Quotes { self: runtime.QuoteUnpickler & runtime.QuoteMatching =>
    *               +- MatchCase
    *               +- TypeBounds
    *               +- NoPrefix
-   * 
+   *
    *  +- MethodTypeKind -+- Contextual
    *                     +- Implicit
    *                     +- Plain
@@ -3273,7 +3273,7 @@ trait Quotes { self: runtime.QuoteUnpickler & runtime.QuoteMatching =>
         def isImplicit: Boolean
         /** Is this the type of parameter clause like `(using X1, ..., Xn)` or `(using x1: X1, x2: X2, ... )` */
         def isContextual: Boolean
-        /** Returns a MethodTypeKind object representing the implicitness of the MethodType parameter clause. */ 
+        /** Returns a MethodTypeKind object representing the implicitness of the MethodType parameter clause. */
         def methodTypeKind: MethodTypeKind
         /** Is this the type of erased parameter clause `(erased x1: X1, ..., xn: Xn)` */
         @deprecated("Use `hasErasedParams` and `erasedParams`", "3.4")
@@ -3428,6 +3428,23 @@ trait Quotes { self: runtime.QuoteUnpickler & runtime.QuoteMatching =>
       def unapply(x: NoPrefix): true
     }
 
+    // ----- Flexible Type --------------------------------------------
+
+    /** Flexible types for explicit nulls */
+    type FlexibleType <: TypeRepr
+
+    /** `TypeTest` that allows testing at runtime in a pattern match if a `TypeRepr` is a `FlexibleType` */
+    given FlexibleTypeTypeTest: TypeTest[TypeRepr, FlexibleType]
+
+    /** Module object of `type FlexibleType`  */
+    val FlexibleType: FlexibleTypeModule
+
+    /** Methods of the module object `val FlexibleType` */
+    trait FlexibleTypeModule { this: FlexibleType.type =>
+      def apply(tp: TypeRepr): FlexibleType
+      def unapply(x: FlexibleType): TypeRepr
+    }
+
     ///////////////
     // CONSTANTS //
     ///////////////