Merge pull request #2282 from ferrous-systems/sovereign-module-of-syn

Move codegen postprocessing to its own module

1 files changed, 46 insertions, 0 deletions

diff --git a/src/codegen/postprocessing/merge_extern_blocks.rs b/src/codegen/postprocessing/merge_extern_blocks.rs
new file mode 100644
index 00000000..2b761494
--- /dev/null
+++ b/src/codegen/postprocessing/merge_extern_blocks.rs
@@ -0,0 +1,46 @@
+use syn::{Item, ItemForeignMod};
+
+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();
+
+    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;
+                    }
+                }
+                // 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 foreign_mod in foreign_mods {
+        items.push(Item::ForeignMod(foreign_mod));
+    }
+}