Add missing version of ValDef.let which also accepts flags

Author: Kalin-Rudnicki

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

@@ -369,6 +369,11 @@ class QuotesImpl private (using val ctx: Context) extends Quotes, QuoteUnpickler
       def unapply(vdef: ValDef): (String, TypeTree, Option[Term]) =
         (vdef.name.toString, vdef.tpt, optional(vdef.rhs))
 
+      def let(owner: Symbol, name: String, rhs: Term, flags: Flags)(body: Ref => Term): Term =
+        val vdef = tpd.SyntheticValDef(name.toTermName, rhs, flags)(using ctx.withOwner(owner))
+        val ref = tpd.ref(vdef.symbol).asInstanceOf[Ref]
+        Block(List(vdef), body(ref))
+
       def let(owner: Symbol, name: String, rhs: Term)(body: Ref => Term): Term =
         val vdef = tpd.SyntheticValDef(name.toTermName, rhs)(using ctx.withOwner(owner))
         val ref = tpd.ref(vdef.symbol).asInstanceOf[Ref]

library/src/scala/quoted/Quotes.scala

@@ -682,6 +682,22 @@ trait Quotes { self: runtime.QuoteUnpickler & runtime.QuoteMatching =>
       def copy(original: Tree)(name: String, tpt: TypeTree, rhs: Option[Term]): ValDef
       def unapply(vdef: ValDef): (String, TypeTree, Option[Term])
 
+      /** Creates a block `{ val <name> = <rhs: Term>; <body(x): Term> }`
+       *
+       *  Usage:
+       *  ```
+       *  ValDef.let(owner, "x", rhs1, Flags.Lazy) { x =>
+       *    ValDef.let(x.symbol.owner, "y", rhs2, Flags.Mutable) { y =>
+       *      // use `x` and `y`
+       *    }
+       *  }
+       *  ```
+       *
+       *  @param flags extra flags to with which the symbol should be constructed. Can be `Private | Protected | Override | Deferred | Final | Param | Implicit | Lazy | Mutable | Local | ParamAccessor | Module | Package | Case | CaseAccessor | Given | Enum | JavaStatic | Synthetic | Artifact`
+       */
+      // Keep: `flags` doc aligned with QuotesImpl's `validValFlags`
+      def let(owner: Symbol, name: String, rhs: Term, flags: Flags)(body: Ref => Term): Term
+
       /** Creates a block `{ val <name> = <rhs: Term>; <body(x): Term> }`
        *
        *  Usage: