Make postprocessing more robust

This is done by merging extern blocks and sorting items in every module
instead of just in the root module.

The tests were changed to use `cxx` namespaces so they effectively check
that items are manipulated correctly in every single module.

1 files changed, 57 insertions, 37 deletions

diff --git a/bindgen/codegen/postprocessing/merge_extern_blocks.rs b/bindgen/codegen/postprocessing/merge_extern_blocks.rs
index 2b761494..05e7e9ef 100644
--- a/bindgen/codegen/postprocessing/merge_extern_blocks.rs
+++ b/bindgen/codegen/postprocessing/merge_extern_blocks.rs
@@ -1,46 +1,66 @@
-use syn::{Item, ItemForeignMod};
+use syn::{
+    visit_mut::{visit_item_mod_mut, VisitMut},
+    Item, ItemForeignMod, ItemMod,
+};
 
-pub(super) fn merge_extern_blocks(items: &mut Vec<Item>) {
-    // Keep all the extern blocks in a different `Vec` for faster search.
-    let mut foreign_mods = Vec::<ItemForeignMod>::new();
+pub(super) fn merge_extern_blocks(item_mod: &mut ItemMod) {
+    Visitor.visit_item_mod_mut(item_mod)
+}
+
+struct Visitor;
 
-    for item in std::mem::take(items) {
-        match item {
-            Item::ForeignMod(ItemForeignMod {
-                attrs,
-                abi,
-                brace_token,
-                items: foreign_items,
-            }) => {
-                let mut exists = false;
-                for foreign_mod in &mut foreign_mods {
-                    // Check if there is a extern block with the same ABI and
-                    // attributes.
-                    if foreign_mod.attrs == attrs && foreign_mod.abi == abi {
-                        // Merge the items of the two blocks.
-                        foreign_mod.items.extend_from_slice(&foreign_items);
-                        exists = true;
-                        break;
+impl VisitMut for Visitor {
+    fn visit_item_mod_mut(&mut self, item_mod: &mut ItemMod) {
+        if let Some((_, ref mut items)) = item_mod.content {
+            // Keep all the extern blocks in a different `Vec` for faster search.
+            let mut extern_blocks = Vec::<ItemForeignMod>::new();
+
+            for item in std::mem::take(items) {
+                if let Item::ForeignMod(ItemForeignMod {
+                    attrs,
+                    abi,
+                    brace_token,
+                    items: extern_block_items,
+                }) = item
+                {
+                    let mut exists = false;
+                    for extern_block in &mut extern_blocks {
+                        // Check if there is a extern block with the same ABI and
+                        // attributes.
+                        if extern_block.attrs == attrs &&
+                            extern_block.abi == abi
+                        {
+                            // Merge the items of the two blocks.
+                            extern_block
+                                .items
+                                .extend_from_slice(&extern_block_items);
+                            exists = true;
+                            break;
+                        }
                     }
+                    // If no existing extern block had the same ABI and attributes, store
+                    // it.
+                    if !exists {
+                        extern_blocks.push(ItemForeignMod {
+                            attrs,
+                            abi,
+                            brace_token,
+                            items: extern_block_items,
+                        });
+                    }
+                } else {
+                    // If the item is not an extern block, we don't have to do anything and just
+                    // push it back.
+                    items.push(item);
                 }
-                // If no existing extern block had the same ABI and attributes, store
-                // it.
-                if !exists {
-                    foreign_mods.push(ItemForeignMod {
-                        attrs,
-                        abi,
-                        brace_token,
-                        items: foreign_items,
-                    });
-                }
             }
-            // If the item is not an extern block, we don't have to do anything.
-            _ => items.push(item),
+
+            // Move all the extern blocks alongside the rest of the items.
+            for extern_block in extern_blocks {
+                items.push(Item::ForeignMod(extern_block));
+            }
         }
-    }
 
-    // Move all the extern blocks alongside the rest of the items.
-    for foreign_mod in foreign_mods {
-        items.push(Item::ForeignMod(foreign_mod));
+        visit_item_mod_mut(self, item_mod)
     }
 }