From 652a8ee6883f08ce7cb55ef372277a535ce4d88f Mon Sep 17 00:00:00 2001
From: Copilot <198982749+Copilot@users.noreply.github.com>
Date: Tue, 15 Jul 2025 17:42:43 -0700
Subject: Add clear diagnostic for unsupported float types in generic value
 parameters (#7737)

* Initial plan

* Add validation and clear error message for float generic parameters

Co-authored-by: csyonghe <2652293+csyonghe@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: csyonghe <2652293+csyonghe@users.noreply.github.com>
---
 source/slang/slang-check-decl.cpp    | 12 ++++++++++++
 source/slang/slang-diagnostic-defs.h |  5 +++++
 2 files changed, 17 insertions(+)

(limited to 'source')

diff --git a/source/slang/slang-check-decl.cpp b/source/slang/slang-check-decl.cpp
index 584b1f081..9853b0097 100644
--- a/source/slang/slang-check-decl.cpp
+++ b/source/slang/slang-check-decl.cpp
@@ -3413,6 +3413,18 @@ void SemanticsDeclHeaderVisitor::visitGenericTypeParamDecl(GenericTypeParamDecl*
 void SemanticsDeclHeaderVisitor::visitGenericValueParamDecl(GenericValueParamDecl* decl)
 {
     checkVarDeclCommon(decl);
+
+    // Validate that the type is supported for generic value parameters
+    if (decl->type.type)
+    {
+        if (!isValidCompileTimeConstantType(decl->type.type))
+        {
+            getSink()->diagnose(
+                decl,
+                Diagnostics::genericValueParameterTypeNotSupported,
+                decl->type.type);
+        }
+    }
 }
 
 void SemanticsDeclHeaderVisitor::visitGenericDecl(GenericDecl* genericDecl)
diff --git a/source/slang/slang-diagnostic-defs.h b/source/slang/slang-diagnostic-defs.h
index fdfa968c3..c549ccca3 100644
--- a/source/slang/slang-diagnostic-defs.h
+++ b/source/slang/slang-diagnostic-defs.h
@@ -1704,6 +1704,11 @@ DIAGNOSTIC(
     Error,
     genericValueParameterMustHaveType,
     "a generic value parameter must be given an explicit type")
+DIAGNOSTIC(
+    30624,
+    Error,
+    genericValueParameterTypeNotSupported,
+    "generic value parameter type '$0' is not supported; only integer and enum types are allowed")
 
 // 307xx: parameters
 DIAGNOSTIC(
-- 
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