Add basic support for namespaces (#1304)

This change adds logic for parsing `namespace` declarations, referencing them, and looking up their members.

* The parser changes are a bit subtle, because that is where we deal with the issue of "re-opening" a namespace. We kludge things a bit by re-using an existing `NamespaceDecl` in the same parent if one is available, and thereby ensure that all the members in the same namespace can see on another.

* In order to allow namespaces to be referenced by name they need to have a type so that a `DeclRefExpr` to them can be formed. For this purpose we introduce `NamespaceType` which is the (singleton) type of a reference to a given namespace.

* The new `NamespaceType` case is detected in the `MemberExpr` checking logic and routed to the same logic that `StaticMemberExpr` uses, and the static lookup logic was extended with support for looking up in a namespace (a thin wrapper around one of the existing worker routines in `slang-lookup.cpp`.

* I made `NamespaceDecl` have a shared base class with `ModuleDecl` in the hopes that this would allow us to allow references to modules by name in the future. That hasn't been tested as part of this change.

* I cleaned up a bunch of logic around `ModuleDecl` holding a `Scope` pointer that was being used for some of the more ad hoc lookup routines in the public API. Those have been switched over to something that is a bit more sensible given the language rules and that doesn't rely on keeping state sititng around on the `ModuleDecl`.

* I added a test case to make sure the new funcitonality works, which includes re-opening a namespace, and it also tests both `.` and `::` operations for lookup in a namespace.

* The main missing feature here is the ability to do something like C++ `using`. It would probably be cleanest if we used `import` for this, since we already have that syntax (and having both `import` and `using` seems like a recipe for confusion). Most of the infrastructure is present to support `import`ing one namespace into another (in a way that wouldn't automatically pollute the namespace for clients), but some careful thought needs to be put into how import of namespaces vs. modules should work.

1 files changed, 39 insertions, 0 deletions

diff --git a/source/slang/slang-syntax.cpp b/source/slang/slang-syntax.cpp
index d479ba32a..1dcaafec5 100644
--- a/source/slang/slang-syntax.cpp
+++ b/source/slang/slang-syntax.cpp
@@ -1280,6 +1280,35 @@ void Type::accept(IValVisitor* visitor, void* extra)
         return this;
     }
 
+    // NamespaceType
+
+    String NamespaceType::ToString()
+    {
+        String result;
+        result.append("namespace ");
+        result.append(m_declRef.toString());
+        return result;
+    }
+
+    bool NamespaceType::EqualsImpl(Type * type)
+    {
+        if (auto namespaceType = as<NamespaceType>(type))
+        {
+            return m_declRef.Equals(namespaceType->m_declRef);
+        }
+        return false;
+    }
+
+    int NamespaceType::GetHashCode()
+    {
+        return m_declRef.GetHashCode();
+    }
+
+    RefPtr<Type> NamespaceType::CreateCanonicalType()
+    {
+        return this;
+    }
+
     // ArithmeticExpressionType
 
     // VectorExpressionType
@@ -2301,6 +2330,16 @@ void Type::accept(IValVisitor* visitor, void* extra)
         return genericDeclRefType;
     }
 
+    RefPtr<NamespaceType> getNamespaceType(
+        Session*                            session,
+        DeclRef<NamespaceDeclBase> const&   declRef)
+    {
+        auto type = new NamespaceType;
+        type->setSession(session);
+        type->m_declRef = declRef;
+        return type;
+    }
+
     RefPtr<SamplerStateType> getSamplerStateType(
         Session*        session)
     {