From 92c9fffb95c92b0bc07eb1c656375928b5cd5c33 Mon Sep 17 00:00:00 2001
From: Darren Wihandi <65404740+fairywreath@users.noreply.github.com>
Date: Fri, 24 Jan 2025 16:12:38 -0500
Subject: [PATCH] improve error message on generic value decls (#6169)

Co-authored-by: Yong He <yonghe@outlook.com>
---
 source/slang/slang-ast-support-types.h        |  1 +
 source/slang/slang-check-decl.cpp             |  9 +++++++-
 source/slang/slang-diagnostic-defs.h          |  6 +++++-
 source/slang/slang-syntax.cpp                 | 13 +++++++++++-
 ...neric-value-parameter-must-have-type.slang | 21 +++++++++++++++++++
 5 files changed, 47 insertions(+), 3 deletions(-)
 create mode 100644 tests/diagnostics/generic-value-parameter-must-have-type.slang

diff --git a/source/slang/slang-ast-support-types.h b/source/slang/slang-ast-support-types.h
index 1d3de9c546..56e07d4304 100644
--- a/source/slang/slang-ast-support-types.h
+++ b/source/slang/slang-ast-support-types.h
@@ -80,6 +80,7 @@ class SyntaxNode;
 SourceLoc getDiagnosticPos(SyntaxNode const* syntax);
 SourceLoc getDiagnosticPos(TypeExp const& typeExp);
 SourceLoc getDiagnosticPos(DeclRefBase* declRef);
+SourceLoc getDiagnosticPos(Decl* decl);
 
 typedef NodeBase* (*SyntaxParseCallback)(Parser* parser, void* userData);
 
diff --git a/source/slang/slang-check-decl.cpp b/source/slang/slang-check-decl.cpp
index 0319eb2609..3453d0538d 100644
--- a/source/slang/slang-check-decl.cpp
+++ b/source/slang/slang-check-decl.cpp
@@ -1775,7 +1775,14 @@ void SemanticsDeclHeaderVisitor::checkVarDeclCommon(VarDeclBase* varDecl)
         {
             if (!varDecl->type.type)
             {
-                getSink()->diagnose(varDecl, Diagnostics::varWithoutTypeMustHaveInitializer);
+                if (as<GenericValueParamDecl>(varDecl))
+                {
+                    getSink()->diagnose(varDecl, Diagnostics::genericValueParameterMustHaveType);
+                }
+                else
+                {
+                    getSink()->diagnose(varDecl, Diagnostics::varWithoutTypeMustHaveInitializer);
+                }
                 varDecl->type.type = m_astBuilder->getErrorType();
             }
         }
diff --git a/source/slang/slang-diagnostic-defs.h b/source/slang/slang-diagnostic-defs.h
index ca99ac11d8..37dfc81147 100644
--- a/source/slang/slang-diagnostic-defs.h
+++ b/source/slang/slang-diagnostic-defs.h
@@ -1421,7 +1421,11 @@ DIAGNOSTIC(
     ambiguousDefaultInitializerForType,
     "more than one default initializer was found for type '$0'")
 DIAGNOSTIC(30623, Error, cannotHaveInitializer, "'$0' cannot have an initializer because it is $1")
-
+DIAGNOSTIC(
+    30623,
+    Error,
+    genericValueParameterMustHaveType,
+    "a generic value parameter must be given an explicit type")
 
 // 307xx: parameters
 DIAGNOSTIC(
diff --git a/source/slang/slang-syntax.cpp b/source/slang/slang-syntax.cpp
index 6fdd5088a6..e479f1b9d8 100644
--- a/source/slang/slang-syntax.cpp
+++ b/source/slang/slang-syntax.cpp
@@ -284,7 +284,18 @@ SourceLoc getDiagnosticPos(DeclRefBase* declRef)
 {
     if (!declRef)
         return SourceLoc();
-    return declRef->getDecl()->loc;
+    return getDiagnosticPos(declRef->getDecl());
+}
+
+SourceLoc getDiagnosticPos(Decl* decl)
+{
+    if (!decl)
+        return SourceLoc();
+    if (decl->getNameLoc().isValid())
+    {
+        return decl->getNameLoc();
+    }
+    return decl->loc;
 }
 
 // !!!!!!!!!!!!!!!!!!!!!!!!!!!!!  Free functions !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
diff --git a/tests/diagnostics/generic-value-parameter-must-have-type.slang b/tests/diagnostics/generic-value-parameter-must-have-type.slang
new file mode 100644
index 0000000000..a7920b86c1
--- /dev/null
+++ b/tests/diagnostics/generic-value-parameter-must-have-type.slang
@@ -0,0 +1,21 @@
+//DIAGNOSTIC_TEST:SIMPLE(filecheck=CHECK): -target spirv
+
+interface ITest
+{
+    static const uint kValue0;
+    static const uint kValue1;
+};
+
+// `TValue1` does not have an explicit type, this should fail to compile.
+// CHECK: error 30623: a generic value parameter
+// Make sure erroneous code is printed out.
+// CHECK: let TValue1>
+struct TestImpl<let TValue0 : uint, let TValue1> : ITest
+{
+    static const uint kValue0 = TValue0;
+    static const uint kValue1 = TValue1;
+};
+
+void computeMain()
+{
+}