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, 13 insertions, 4 deletions

diff --git a/source/slang/slang-check-decl.cpp b/source/slang/slang-check-decl.cpp
index 0c42817c8..1659a161b 100644
--- a/source/slang/slang-check-decl.cpp
+++ b/source/slang/slang-check-decl.cpp
@@ -1430,7 +1430,7 @@ bool SemanticsVisitor::shouldSkipChecking(Decl* decl, DeclCheckState state)
     return false;
 }
 
-void SemanticsVisitor::_validateCircularVarDefinition(VarDeclBase* varDecl)
+IntVal* SemanticsVisitor::_validateCircularVarDefinition(VarDeclBase* varDecl)
 {
     // The easiest way to test if the declaration is circular is to
     // validate it as a constant.
@@ -1444,8 +1444,11 @@ void SemanticsVisitor::_validateCircularVarDefinition(VarDeclBase* varDecl)
     //
     //
     if (!isScalarIntegerType(varDecl->type))
-        return;
-    tryConstantFoldDeclRef(DeclRef<VarDeclBase>(varDecl), ConstantFoldingKind::LinkTime, nullptr);
+        return nullptr;
+    return tryConstantFoldDeclRef(
+        DeclRef<VarDeclBase>(varDecl),
+        ConstantFoldingKind::LinkTime,
+        nullptr);
 }
 
 void SemanticsDeclModifiersVisitor::visitStructDecl(StructDecl* structDecl)
@@ -2350,7 +2353,13 @@ void SemanticsDeclBodyVisitor::checkVarDeclCommon(VarDeclBase* varDecl)
         // a constant with a circular definition.
         //
         varDecl->setCheckState(DeclCheckState::DefinitionChecked);
-        _validateCircularVarDefinition(varDecl);
+
+        // Update constant value
+        //
+        if (!varDecl->val)
+        {
+            varDecl->val = _validateCircularVarDefinition(varDecl);
+        }
     }
     else
     {