Initial implementation for decl-tree reflection API (#4666)

* Initial implementation for decl-tree reflection API

This patch adds Slang API methods for walking all the declarations in the AST.

We expose this functionality through an abstract `DeclReflection` class that can be a type, function or a variable declaration.
We also provide ways to cast the decl to a `FunctionReflection`, `TypeReflection` or `VariableReflection` and traverse through the child nodes (for instance, a struct type will have component variable declarations)

This patch also adds `ISlangInternal` as an internal COM interface to allow us to cast IGlobalSession to the internal Session pointer while bypassing any wrappers (such as the capture interface)

* Update slang.h

* Remove `ISlangInternal` (its causing a diamond pattern w.r.t `ISlangUnknown`) and use `ComPtr` for proper ref management.

* Update unit-test-decl-tree-reflection.cpp

* Change `FunctionDeclBase` to use `DeclRef` instead of directly using the decl.

* Update slang-reflection-api.cpp

1 files changed, 21 insertions, 4 deletions

diff --git a/source/slang/slang.cpp b/source/slang/slang.cpp
index f28d3cdeb..f440ce3cb 100644
--- a/source/slang/slang.cpp
+++ b/source/slang/slang.cpp
@@ -546,11 +546,23 @@ SlangResult Session::_readBuiltinModule(ISlangFileSystem* fileSystem, Scope* sco
     return SLANG_OK;
 }
 
-ISlangUnknown* Session::getInterface(const Guid& guid)
+SLANG_NO_THROW SlangResult SLANG_MCALL Session::queryInterface(SlangUUID const& uuid, void** outObject)
 {
-    if(guid == ISlangUnknown::getTypeGuid() || guid == IGlobalSession::getTypeGuid())
-        return asExternal(this);
-    return nullptr;
+    if (uuid == Session::getTypeGuid())
+    {
+        addReference();
+        *outObject = static_cast<Session*>(this);
+        return SLANG_OK;
+    }
+
+    if (uuid == ISlangUnknown::getTypeGuid() && uuid == IGlobalSession::getTypeGuid())
+    {
+        addReference();
+        *outObject = static_cast<slang::IGlobalSession*>(this);
+        return SLANG_OK;
+    }
+
+    return SLANG_E_NO_INTERFACE;
 }
 
 static size_t _getStructureSize(const uint8_t* src)
@@ -4070,6 +4082,11 @@ void Module::buildHash(DigestBuilder<SHA1>& builder)
     builder.append(computeDigest());
 }
 
+slang::DeclReflection* Module::getModuleReflection()
+{
+    return (slang::DeclReflection*)m_moduleDecl;
+}
+
 SHA1::Digest Module::computeDigest()
 {
     if (m_digest == SHA1::Digest())