tint: Add TINT_REFLECT() & ForeachField()

This uses template and macro magic to reflect the fields of a class.

Dawn:
* Reflect the fields of the types that are used by Dawn's stream::Stream<T> specializations, and use tint::ForeachField() to call StreamIn().

Fuzzers:
* Replace tint::fuzzers::DataBuilder::BuildImpl<T> specializations with the new reflection system.
* static_assert that the type is either POD or reflected. Add a specialization for std::optional which was missing.

Move tint::transform::BindingPoints into MultiplanarExternalTexture, as this is only used by MultiplanarExternalTexture.

All this reduces fragility of the struct declarations slipping out of sync with the uses.

Bug: tint:1640
Change-Id: I08729c1c356f1b427e85983efe3c2678fc2ce717
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/101001
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Commit-Queue: Ben Clayton <bclayton@chromium.org>

src/tint/transform/multiplanar_external_texture.h

@@ -28,30 +28,33 @@ namespace tint::transform {
 /// BindingPoint is an alias to sem::BindingPoint
 using BindingPoint = sem::BindingPoint;
 
-/// This struct identifies the binding groups and locations for new bindings to
-/// use when transforming a texture_external instance.
-struct BindingPoints {
-    /// The desired binding location of the texture_2d representing plane #1 when
-    /// a texture_external binding is expanded.
-    BindingPoint plane_1;
-    /// The desired binding location of the ExternalTextureParams uniform when a
-    /// texture_external binding is expanded.
-    BindingPoint params;
-};
-
 /// Within the MultiplanarExternalTexture transform, each instance of a
 /// texture_external binding is unpacked into two texture_2d<f32> bindings
 /// representing two possible planes of a texture and a uniform buffer binding
 /// representing a struct of parameters. Calls to textureLoad or
 /// textureSampleLevel that contain a texture_external parameter will be
 /// transformed into a newly generated version of the function, which can
-/// perform the desired operation on a single RGBA plane or on seperate Y and UV
+/// perform the desired operation on a single RGBA plane or on separate Y and UV
 /// planes, and do colorspace conversions including yuv->rgb conversion, gamma
 /// decoding, gamut conversion, and gamma encoding steps. Specifically
 // for BT.709 to SRGB conversion, it takes the fast path only doing the yuv->rgb
 // step and skipping all other steps.
 class MultiplanarExternalTexture final : public Castable<MultiplanarExternalTexture, Transform> {
   public:
+    /// This struct identifies the binding groups and locations for new bindings to
+    /// use when transforming a texture_external instance.
+    struct BindingPoints {
+        /// The desired binding location of the texture_2d representing plane #1 when
+        /// a texture_external binding is expanded.
+        BindingPoint plane_1;
+        /// The desired binding location of the ExternalTextureParams uniform when a
+        /// texture_external binding is expanded.
+        BindingPoint params;
+
+        /// Reflect the fields of this class so that it can be used by tint::ForeachField()
+        TINT_REFLECT(plane_1, params);
+    };
+
     /// BindingsMap is a map where the key is the binding location of a
     /// texture_external and the value is a struct containing the desired
     /// locations for new bindings expanded from the texture_external instance.

src/tint/transform/vertex_pulling.h

@@ -20,6 +20,7 @@
 #include <unordered_map>
 #include <vector>
 
+#include "src/tint/reflection.h"
 #include "src/tint/transform/transform.h"
 
 namespace tint::transform {
@@ -72,6 +73,9 @@ struct VertexAttributeDescriptor {
     uint32_t offset;
     /// The shader location used for the attribute
     uint32_t shader_location;
+
+    /// Reflect the fields of this class so that it can be used by tint::ForeachField()
+    TINT_REFLECT(format, offset, shader_location);
 };
 
 /// Describes a buffer containing multiple vertex attributes
@@ -102,6 +106,9 @@ struct VertexBufferLayoutDescriptor {
     VertexStepMode step_mode = VertexStepMode::kVertex;
     /// The vertex attributes
     std::vector<VertexAttributeDescriptor> attributes;
+
+    /// Reflect the fields of this class so that it can be used by tint::ForeachField()
+    TINT_REFLECT(array_stride, step_mode, attributes);
 };
 
 /// Describes vertex state, which consists of many buffers containing vertex
@@ -154,6 +161,9 @@ class VertexPulling final : public Castable<VertexPulling, Transform> {
         /// The "group" we will put all our vertex buffers into (as storage buffers)
         /// Default to 4 as it is past the limits of user-accessible groups
         uint32_t pulling_group = 4u;
+
+        /// Reflect the fields of this class so that it can be used by tint::ForeachField()
+        TINT_REFLECT(entry_point_name, vertex_state, pulling_group);
     };
 
     /// Constructor