Add the possibility to create a typeSymbol in the Quotes API

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

@@ -2613,6 +2613,11 @@ class QuotesImpl private (using val ctx: Context) extends Quotes, QuoteUnpickler
       def newBind(owner: Symbol, name: String, flags: Flags, tpe: TypeRepr): Symbol =
         checkValidFlags(flags.toTermFlags, Flags.validBindFlags)
         dotc.core.Symbols.newSymbol(owner, name.toTermName, flags | dotc.core.Flags.Case, tpe)
+
+      def newType(owner: Symbol, name: String, flags: Flags, tpe: TypeRepr, privateWithin: Symbol): Symbol =
+        checkValidFlags(flags.toTypeFlags, Flags.validTypeFlags)
+        dotc.core.Symbols.newSymbol(owner, name.toTypeName, flags | dotc.core.Flags.Deferred, tpe, privateWithin)
+
       def noSymbol: Symbol = dotc.core.Symbols.NoSymbol
 
       private inline def checkValidFlags(inline flags: Flags, inline valid: Flags): Unit =
@@ -2953,6 +2958,9 @@ class QuotesImpl private (using val ctx: Context) extends Quotes, QuoteUnpickler
 
       // Keep: aligned with Quotes's `newBind` doc
       private[QuotesImpl] def validBindFlags: Flags = Case // Flags that could be allowed: Implicit | Given | Erased
+
+      private[QuotesImpl] def validTypeFlags: Flags = Private | Protected | Override | Deferred | Final | Infix | Local
+
     end Flags
 
     given FlagsMethods: FlagsMethods with

library/src/scala/quoted/Quotes.scala

@@ -3915,6 +3915,23 @@ trait Quotes { self: runtime.QuoteUnpickler & runtime.QuoteMatching =>
       // Keep: `flags` doc aligned with QuotesImpl's `validBindFlags`
       def newBind(parent: Symbol, name: String, flags: Flags, tpe: TypeRepr): Symbol
 
+      /** Generate a new type symbol with the given parent, name and type
+        * 
+        *  This symbol starts without an accompanying definition.
+        *  It is the meta-programmer's responsibility to provide exactly one corresponding definition by passing
+        *  this symbol to the TypeDef constructor.
+        *
+        *  @param parent The owner of the type
+        *  @param name The name of the type
+        *  @param flags extra flags to with which symbol can be constructed. `Deferred` flag will be added. Can be `Private` | `Protected` | `Override` | `Deferred` | `Final` | `Infix` | `Local`
+        *  @param tpe The rhs or bounds of the type
+        *  @note As a macro can only splice code into the point at which it is expanded, all generated symbols must be
+        *        direct or indirect children of the reflection context's owner.
+        */
+      @experimental
+      // Keep: `flags` doc aligned with QuotesImpl's `validTypeFlags`
+      def newType(parent: Symbol, name: String, flags: Flags, tpe: TypeRepr, privateWithin: Symbol): Symbol
+
       /** Definition not available */
       def noSymbol: Symbol
 

tests/pos-macros/quoted-sym-newtype/Macro_1.scala

@@ -0,0 +1,10 @@
+import scala.quoted.*
+
+inline def testMacro = ${ testImpl }
+
+def testImpl(using Quotes): Expr[Unit] = { 
+    import quotes.reflect.*
+    val sym = Symbol.newType(Symbol.spliceOwner, "mytype", Flags.EmptyFlags, TypeRepr.of[String], Symbol.noSymbol)
+    assert(TypeDef(sym).show == "type mytype = java.lang.String")
+    '{ () }
+}

tests/pos-macros/quoted-sym-newtype/Test_2.scala

@@ -0,0 +1,2 @@
+
+def test = testMacro