From 743cc0b0f79a5886267ef6da2d5b101b6e98c54e Mon Sep 17 00:00:00 2001
From: Nicolas Stucki <nicolas.stucki@gmail.com>
Date: Mon, 22 Apr 2024 09:39:38 +0200
Subject: [PATCH] Add type argument encoding to SPLICEPATTERN

Future proof for #18271.
---
 compiler/src/dotty/tools/dotc/core/tasty/TreePickler.scala   | 4 ++++
 compiler/src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala | 3 ++-
 tasty/src/dotty/tools/tasty/TastyFormat.scala                | 2 +-
 3 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/compiler/src/dotty/tools/dotc/core/tasty/TreePickler.scala b/compiler/src/dotty/tools/dotc/core/tasty/TreePickler.scala
index 55d25eeb3654..f8a0f725ea52 100644
--- a/compiler/src/dotty/tools/dotc/core/tasty/TreePickler.scala
+++ b/compiler/src/dotty/tools/dotc/core/tasty/TreePickler.scala
@@ -725,10 +725,14 @@ class TreePickler(pickler: TastyPickler, attributes: Attributes) {
             bindings.foreach(pickleTree)
           }
         case SplicePattern(pat, args) =>
+          val targs = Nil // SplicePattern `targs` will be added with #18271
           writeByte(SPLICEPATTERN)
           withLength {
             pickleTree(pat)
             pickleType(tree.tpe)
+            for targ <- targs do
+              writeByte(EXPLICITtpt)
+              pickleTree(targ)
             args.foreach(pickleTree)
           }
         case Hole(_, idx, args, _) =>
diff --git a/compiler/src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala b/compiler/src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala
index ee3c98632b95..64ea2d497295 100644
--- a/compiler/src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala
+++ b/compiler/src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala
@@ -1566,7 +1566,8 @@ class TreeUnpickler(reader: TastyReader,
             case SPLICEPATTERN =>
               val pat = readTree()
               val patType = readType()
-              val args = until(end)(readTree())
+              val (targs, args) = until(end)(readTree()).span(_.isType)
+              assert(targs.isEmpty, "unexpected type arguments in SPLICEPATTERN") // `targs` will be needed for #18271. Until this fearure is added they should be empty.
               SplicePattern(pat, args, patType)
             case HOLE =>
               readHole(end, isTerm = true)
diff --git a/tasty/src/dotty/tools/tasty/TastyFormat.scala b/tasty/src/dotty/tools/tasty/TastyFormat.scala
index 413702ea0d71..164243d3b469 100644
--- a/tasty/src/dotty/tools/tasty/TastyFormat.scala
+++ b/tasty/src/dotty/tools/tasty/TastyFormat.scala
@@ -112,7 +112,7 @@ Standard-Section: "ASTs" TopLevelStat*
                   SELECTouter    Length levels_Nat qual_Term underlying_Type       -- Follow `levels` outer links, starting from `qual`, with given `underlying` type
                   QUOTE          Length body_Term bodyTpe_Type                     -- Quoted expression `'{ body }` of a body typed as `bodyTpe`
                   SPLICE         Length expr_Term tpe_Type                         -- Spliced expression `${ expr }` typed as `tpe`
-                  SPLICEPATTEN   Length pat_Term tpe_Type args_Term*               -- Pattern splice `${pat}` or `$pat(args*)` in a quoted pattern of type `tpe`
+                  SPLICEPATTEN   Length pat_Term tpe_Type targs_Type* args_Term*   -- Pattern splice `${pat}` or `$pat[targs*](args*)` in a quoted pattern of type `tpe`.
     -- patterns:
                   BIND           Length boundName_NameRef patType_Type pat_Term    -- name @ pat, wherev `patType` is the type of the bound symbol
                   ALTERNATIVE    Length alt_Term*                                  -- alt1 | ... | altn   as a pattern