3 files changed, 47 insertions, 1 deletions
diff --git a/source/slang/slang-check-decl.cpp b/source/slang/slang-check-decl.cpp
index 7a0dcb06f..f8a80c09b 100644
--- a/source/slang/slang-check-decl.cpp
+++ b/source/slang/slang-check-decl.cpp
@@ -10405,7 +10405,16 @@ void SemanticsDeclHeaderVisitor::visitAbstractStorageDeclCommon(ContainerDecl* d
 
 void SemanticsDeclHeaderVisitor::visitSubscriptDecl(SubscriptDecl* decl)
 {
-    decl->returnType = CheckUsableType(decl->returnType, decl);
+    // __subscript needs to have a return type specified. Check if return type
+    // is missing (represented as IncompleteExpr) and return an error.
+    if (decl->returnType.exp && as<IncompleteExpr>(decl->returnType.exp))
+    {
+        getSink()->diagnose(decl, Diagnostics::subscriptMustHaveReturnType);
+    }
+    else if (decl->returnType.exp)
+    {
+        decl->returnType = CheckUsableType(decl->returnType, decl);
+    }
 
     visitAbstractStorageDeclCommon(decl);
 
diff --git a/source/slang/slang-diagnostic-defs.h b/source/slang/slang-diagnostic-defs.h
index 3babc9a56..0814bb2a0 100644
--- a/source/slang/slang-diagnostic-defs.h
+++ b/source/slang/slang-diagnostic-defs.h
@@ -1710,6 +1710,11 @@ DIAGNOSTIC(
     Error,
     multiDimensionalArrayNotSupported,
     "multi-dimensional array is not supported.")
+DIAGNOSTIC(
+    30901,
+    Error,
+    subscriptMustHaveReturnType,
+    "__subscript declaration must have a return type specified after '->'")
 // 310xx: properties
 
 // 311xx: accessors
diff --git a/tests/diagnostics/subscript-missing-return-type.slang b/tests/diagnostics/subscript-missing-return-type.slang
new file mode 100644
index 000000000..23c2cda5e
--- /dev/null
+++ b/tests/diagnostics/subscript-missing-return-type.slang
@@ -0,0 +1,32 @@
+// Test that __subscript without return type produces proper error message
+
+//TEST:SIMPLE(filecheck=CHECK): -target spirv
+
+struct MyType
+{
+    int val[12];
+    
+    // CHECK: ([[# @LINE+1]]): error 30901: __subscript declaration must have a return type specified after '->'
+    __subscript(int x, int y)
+    {
+        get { return val[x*3 + y]; }
+    }
+}
+
+// This should compile fine - subscript with return type
+struct MyType2
+{
+    int val[12];
+    __subscript(int x, int y) -> int
+    {
+        get { return val[x*3 + y]; }
+    }
+}
+
+[shader("compute")]
+[numthreads(1,1,1)]
+void computeMain()
+{
+    MyType2 obj;
+    int v = obj[1, 2];
+} 
+\ No newline at end of file