BLI: improve CPPType system

* Support bidirectional type lookups. E.g. finding the base type of a
  field was supported, but not the other way around. This also removes
  the todo in `get_vector_type`. To achieve this, types have to be
  registered up-front.
* Separate `CPPType` from other "type traits". For example, previously
  `ValueOrFieldCPPType` adds additional behavior on top of `CPPType`.
  Previously, it was a subclass, now it just contains a reference to the
  `CPPType` it corresponds to. This follows the composition-over-inheritance
  idea. This makes it easier to have self-contained "type traits" without
  having to put everything into `CPPType`.

Differential Revision: https://developer.blender.org/D16479

1 files changed, 44 insertions, 0 deletions

diff --git a/source/blender/blenlib/BLI_cpp_types.hh b/source/blender/blenlib/BLI_cpp_types.hh
new file mode 100644
index 00000000000..596090b95e5
--- /dev/null
+++ b/source/blender/blenlib/BLI_cpp_types.hh
@@ -0,0 +1,44 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#pragma once
+
+#include "BLI_cpp_type.hh"
+#include "BLI_vector.hh"
+
+namespace blender {
+
+/**
+ * Contains information about how to deal with a #Vector<T> generically.
+ */
+class VectorCPPType {
+ public:
+  /** The #Vector<T> itself. */
+  const CPPType &self;
+  /** The type stored in the vector. */
+  const CPPType &value;
+
+  template<typename ValueType> VectorCPPType(TypeTag<ValueType> /*value_type*/);
+
+  /**
+   * Try to find the #VectorCPPType that corresponds to a #CPPType.
+   */
+  static const VectorCPPType *get_from_self(const CPPType &self);
+  /**
+   * Try to find the #VectorCPPType that wraps a vector containing the given value type.
+   * This only works when the vector type has been created with #BLI_VECTOR_CPP_TYPE_MAKE.
+   */
+  static const VectorCPPType *get_from_value(const CPPType &value);
+
+  template<typename ValueType> static const VectorCPPType &get()
+  {
+    static const VectorCPPType &type = VectorCPPType::get_impl<std::decay_t<ValueType>>();
+    return type;
+  }
+
+  template<typename ValueType> static const VectorCPPType &get_impl();
+
+ private:
+  void register_self();
+};
+
+}  // namespace blender