expose value of constant integers in module reflection (#6367)

* Expose value of constant integers in module reflection

This commit adds `VariableReflection::getDefaultValueInt` to get the value of a variable if it is a compile-time constant integer.
TODO: currently it works only if the initializer expression is an integer literal, references to other constant values are not handled.

* Update VarDecl folded constant value during DeclBodyVisitor

Constant folding for integer values is already done internally by _validateCircularVarDefinition, this just reuses the result.

* Address review comments & formatting

* Formatting

---------

Co-authored-by: Yong He <yonghe@outlook.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/source/slang/slang-reflection-api.cpp b/source/slang/slang-reflection-api.cpp
index 52047a751..9295bfdf6 100644
--- a/source/slang/slang-reflection-api.cpp
+++ b/source/slang/slang-reflection-api.cpp
@@ -3164,6 +3164,22 @@ SLANG_API bool spReflectionVariable_HasDefaultValue(SlangReflectionVariable* inV
     return false;
 }
 
+SLANG_API SlangResult
+spReflectionVariable_GetDefaultValueInt(SlangReflectionVariable* inVar, int64_t* rs)
+{
+    auto decl = convert(inVar).getDecl();
+    if (auto varDecl = as<VarDeclBase>(decl))
+    {
+        if (auto constantVal = as<ConstantIntVal>(varDecl->val))
+        {
+            *rs = constantVal->getValue();
+            return 0;
+        }
+    }
+
+    return SLANG_E_INVALID_ARG;
+}
+
 SLANG_API SlangReflectionGeneric* spReflectionVariable_GetGenericContainer(
     SlangReflectionVariable* var)
 {