From 3666c66e26f90b10031578e9c8b8f2ea118aecf9 Mon Sep 17 00:00:00 2001
From: Yong He <yonghe@outlook.com>
Date: Fri, 17 Jan 2025 08:55:57 -0800
Subject: Fix prebound parameter pack - argument list matching logic. (#6111)

* Fix prebound parameter pack - argument list matching logic.

* Move tests.

* Fix.
---
 source/slang/slang-ast-decl-ref.cpp                |  2 +-
 source/slang/slang-check-overload.cpp              | 18 +++++++++++++-
 .../generics/prebound-variadic-pack.slang          | 28 ++++++++++++++++++++++
 .../generics/variadic-tuple-field.slang            | 22 +++++++++++++++++
 4 files changed, 68 insertions(+), 2 deletions(-)
 create mode 100644 tests/language-feature/generics/prebound-variadic-pack.slang
 create mode 100644 tests/language-feature/generics/variadic-tuple-field.slang

diff --git a/source/slang/slang-ast-decl-ref.cpp b/source/slang/slang-ast-decl-ref.cpp
index 3025381ea..9f140a524 100644
--- a/source/slang/slang-ast-decl-ref.cpp
+++ b/source/slang/slang-ast-decl-ref.cpp
@@ -318,7 +318,7 @@ void DeclRefBase::toText(StringBuilder& out)
         return;
     }
 
-    if (as<GenericTypeParamDecl>(this->getDecl()))
+    if (as<GenericTypeParamDeclBase>(this->getDecl()))
     {
         SLANG_ASSERT(as<DirectDeclRef>(this));
         out << this->getDecl()->getName()->text;
diff --git a/source/slang/slang-check-overload.cpp b/source/slang/slang-check-overload.cpp
index fcc6780b6..1ab3aa5b0 100644
--- a/source/slang/slang-check-overload.cpp
+++ b/source/slang/slang-check-overload.cpp
@@ -10,6 +10,17 @@
 
 namespace Slang
 {
+
+bool isFreeFormTypePackParam(SemanticsVisitor* visitor, Type* type, ParamDecl* paramDecl)
+{
+    if (auto declRef = isDeclRefTypeOf<GenericTypePackParamDecl>(type))
+    {
+        return visitor->GetOuterGeneric(declRef.getDecl()) ==
+               visitor->GetOuterGeneric(paramDecl->parentDecl);
+    }
+    return false;
+}
+
 SemanticsVisitor::ParamCounts SemanticsVisitor::CountParameters(
     FilteredMemberRefList<ParamDecl> params)
 {
@@ -25,10 +36,15 @@ SemanticsVisitor::ParamCounts SemanticsVisitor::CountParameters(
                 counts.required += typePack->getTypeCount();
                 allowedArgCountToAdd = typePack->getTypeCount();
             }
-            else
+            else if (isFreeFormTypePackParam(this, paramType, param.getDecl()))
             {
                 counts.allowed = -1;
             }
+            else
+            {
+                counts.required++;
+                counts.allowed++;
+            }
         }
         else if (!param.getDecl()->initExpr)
         {
diff --git a/tests/language-feature/generics/prebound-variadic-pack.slang b/tests/language-feature/generics/prebound-variadic-pack.slang
new file mode 100644
index 000000000..01edce8f9
--- /dev/null
+++ b/tests/language-feature/generics/prebound-variadic-pack.slang
@@ -0,0 +1,28 @@
+//TEST:SIMPLE(filecheck=CHECK): -target spirv
+
+struct Set<each T>
+{
+    Tuple<expand each T> data;
+    void f(expand each T v){}
+    void h<each U>(U x){}
+    void g(expand each T d)
+    {
+        //CHECK-NOT: ([[# @LINE+1]]): error
+        f(expand each d); // OK
+
+        //CHECK-NOT: ([[# @LINE+1]]): error
+        h(54); // OK, specializing free-form parameter U.
+
+        //CHECK: ([[# @LINE+1]]): error
+        f(); // error, cannot call f without arguments.
+
+        //CHECK: ([[# @LINE+1]]): error
+        f(5); // error, cannot call f with different type pack.
+    }
+}
+
+[numthreads(1,1,1)]
+void computeMain()
+{
+    Set<float> v;
+}
\ No newline at end of file
diff --git a/tests/language-feature/generics/variadic-tuple-field.slang b/tests/language-feature/generics/variadic-tuple-field.slang
new file mode 100644
index 000000000..b5ebc4fb3
--- /dev/null
+++ b/tests/language-feature/generics/variadic-tuple-field.slang
@@ -0,0 +1,22 @@
+//TEST:COMPARE_COMPUTE(filecheck-buffer=CHECK): -output-using-type
+
+struct Set<each T>
+{
+    Tuple<expand each T> data;
+    void f(expand each T v){}
+    __init(expand each T d) {
+        f(d);
+        data = makeTuple(d);
+    }
+}
+
+//TEST_INPUT: set outputBuffer = out ubuffer(data=[0 0 0 0], stride=4)
+RWStructuredBuffer<float> outputBuffer;
+
+[numthreads(1,1,1)]
+void computeMain()
+{
+    let set = Set<float>(1.0);
+    outputBuffer[0] = set.data._0;
+    // CHECK: 1.0
+}
-- 
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