From d1a13a730406646029cedd018bb9806943209baa Mon Sep 17 00:00:00 2001
From: Yong He <yonghe@outlook.com>
Date: Fri, 17 Jan 2025 14:43:31 -0800
Subject: Allow __subscript<T> syntax. (#6124)

* Allow __subscript<T> syntax.

* Fix.
---
 source/slang/slang-parser.cpp                      | 44 +++++++++++++---------
 .../generics/generic-subscript.slang               | 24 ++++++++++++
 2 files changed, 51 insertions(+), 17 deletions(-)
 create mode 100644 tests/language-feature/generics/generic-subscript.slang

diff --git a/source/slang/slang-parser.cpp b/source/slang/slang-parser.cpp
index 6ae41a2eb..98cfd121c 100644
--- a/source/slang/slang-parser.cpp
+++ b/source/slang/slang-parser.cpp
@@ -3932,28 +3932,38 @@ static void parseStorageDeclBody(Parser* parser, ContainerDecl* decl)
 
 static NodeBase* parseSubscriptDecl(Parser* parser, void* /*userData*/)
 {
-    SubscriptDecl* decl = parser->astBuilder->create<SubscriptDecl>();
-    parser->FillPosition(decl);
-    parser->PushScope(decl);
+    return parseOptGenericDecl(
+        parser,
+        [&](GenericDecl* genericParent)
+        {
+            SubscriptDecl* decl = parser->astBuilder->create<SubscriptDecl>();
+            parser->FillPosition(decl);
+            parser->PushScope(decl);
 
-    // TODO: the use of this name here is a bit magical...
-    decl->nameAndLoc.name = getName(parser, "operator[]");
+            // TODO: the use of this name here is a bit magical...
+            decl->nameAndLoc.name = getName(parser, "operator[]");
 
-    parseParameterList(parser, decl);
+            parseParameterList(parser, decl);
 
-    if (AdvanceIf(parser, TokenType::RightArrow))
-    {
-        decl->returnType = parser->ParseTypeExp();
-    }
-    else
-    {
-        decl->returnType.exp = parser->astBuilder->create<IncompleteExpr>();
-    }
+            if (AdvanceIf(parser, TokenType::RightArrow))
+            {
+                decl->returnType = parser->ParseTypeExp();
+            }
+            else
+            {
+                decl->returnType.exp = parser->astBuilder->create<IncompleteExpr>();
+            }
 
-    parseStorageDeclBody(parser, decl);
+            auto funcScope = parser->currentScope;
+            parser->PopScope();
+            maybeParseGenericConstraints(parser, genericParent);
+            parser->PushScope(funcScope);
 
-    parser->PopScope();
-    return decl;
+            parseStorageDeclBody(parser, decl);
+
+            parser->PopScope();
+            return decl;
+        });
 }
 
 /// Peek in the token stream and return `true` if it looks like a modern-style variable declaration
diff --git a/tests/language-feature/generics/generic-subscript.slang b/tests/language-feature/generics/generic-subscript.slang
new file mode 100644
index 000000000..87eec3045
--- /dev/null
+++ b/tests/language-feature/generics/generic-subscript.slang
@@ -0,0 +1,24 @@
+//TEST:COMPARE_COMPUTE(filecheck-buffer=CHECK): -output-using-type
+
+//TEST_INPUT: set output = out ubuffer(data=[0 0 0 0], stride=4)
+RWStructuredBuffer<float> output;
+
+struct Tx
+{
+    float x;
+    __subscript<I>(I index) -> float
+        where I:IInteger
+    {
+        get { return x + index.toInt(); }
+        set { x = newValue;}
+    }
+}
+
+[numthreads(1,1,1)]
+void computeMain()
+{
+    Tx obj;
+    obj[0] = 3.0;
+    // CHECK: 5.0
+    output[0] = obj[2];
+}
\ No newline at end of file
-- 
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