fix: parse selector hashes in sol macro (#730)

* fix: parse selectors in sol macro

* run fmt

* add clippy lint suggestoins

* code formatting

* more formatting

* feat: include namespaces, add tests

* chore: use [u8; 4]

---------

Co-authored-by: DaniPopes <57450786+DaniPopes@users.noreply.github.com>

crates/sol-macro-expander/src/expand/mod.rs

@@ -15,6 +15,8 @@ use proc_macro_error2::{abort, emit_error};
 use quote::{format_ident, quote, TokenStreamExt};
 use std::{
     borrow::Borrow,
+    collections::HashMap,
+    fmt,
     fmt::Write,
     sync::atomic::{AtomicBool, Ordering},
 };
@@ -157,7 +159,8 @@ impl<'ast> ExpCtxt<'ast> {
 
         if !self.all_items.0.is_empty() {
             self.resolve_custom_types();
-            if self.mk_overloads_map().is_err() {
+            // Selector collisions requires resolved types.
+            if self.mk_overloads_map().is_err() || self.check_selector_collisions().is_err() {
                 abort = true;
             }
         }
@@ -254,6 +257,82 @@ impl<'ast> ExpCtxt<'ast> {
         }
     }
 
+    /// Checks for function and error selector collisions in the resolved items.
+    fn check_selector_collisions(&mut self) -> std::result::Result<(), ()> {
+        #[derive(Clone, Copy)]
+        enum SelectorKind {
+            Function,
+            Error,
+            // We can ignore events since their selectors are 32 bytes which are unlikely to
+            // collide.
+            // Event,
+        }
+
+        impl fmt::Display for SelectorKind {
+            fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+                match self {
+                    Self::Function => "function",
+                    Self::Error => "error",
+                    // Self::Event => "event",
+                }
+                .fmt(f)
+            }
+        }
+
+        let mut result = Ok(());
+
+        let mut selectors = vec![HashMap::new(); 3];
+        let all_items = std::mem::take(&mut self.all_items);
+        for (namespace, items) in &all_items.0 {
+            self.with_namespace(namespace.clone(), |this| {
+                selectors.iter_mut().for_each(|s| s.clear());
+                for (_, &item) in items {
+                    let (kind, selector) = match item {
+                        Item::Function(function) => {
+                            (SelectorKind::Function, this.function_selector(function))
+                        }
+                        Item::Error(error) => (SelectorKind::Error, this.error_selector(error)),
+                        // Item::Event(event) => (SelectorKind::Event, this.event_selector(event)),
+                        _ => continue,
+                    };
+                    let selector: [u8; 4] = selector.array.try_into().unwrap();
+                    // 0x00000000 or 0xffffffff are reserved for custom errors.
+                    if matches!(kind, SelectorKind::Error)
+                        && (selector == [0, 0, 0, 0] || selector == [0xff, 0xff, 0xff, 0xff])
+                    {
+                        emit_error!(
+                            item.span(),
+                            "{kind} selector `{}` is reserved",
+                            hex::encode_prefixed(selector),
+                        );
+                        result = Err(());
+                        continue;
+                    }
+                    match selectors[kind as usize].entry(selector) {
+                        std::collections::hash_map::Entry::Vacant(entry) => {
+                            entry.insert(item);
+                        }
+                        std::collections::hash_map::Entry::Occupied(entry) => {
+                            result = Err(());
+                            let other = *entry.get();
+                            emit_error!(
+                                item.span(),
+                                "{kind} selector `{}` collides with `{}`",
+                                hex::encode_prefixed(selector),
+                                other.name().unwrap();
+
+                                note = other.span() => "other declaration is here";
+                            );
+                        }
+                    }
+                }
+            })
+        }
+        self.all_items = all_items;
+
+        result
+    }
+
     fn mk_overloads_map(&mut self) -> std::result::Result<(), ()> {
         let mut overloads_map = std::mem::take(&mut self.overloads);
 

crates/sol-types/tests/ui/collisions.rs

@@ -0,0 +1,38 @@
+use alloy_sol_types::sol;
+
+// https://github.com/alloy-rs/core/issues/729
+
+sol! {
+    error func_2093253501(bytes);
+    error transfer(address,uint256);
+
+    function func_2093253501(bytes);
+    function transfer(address,uint256);
+
+    error BlazingIt4490597615();
+
+    contract A {
+        error func_2093253501(bytes);
+        error transfer(address,uint256);
+
+        function func_2093253501(bytes);
+        function transfer(address,uint256);
+
+        error BlazingIt4490597615();
+    }
+}
+
+// This is OK.
+mod namespaced {
+    use alloy_sol_types::sol;
+
+    sol! {
+        function func_2093253501(bytes);
+
+        contract B {
+            function transfer(address,uint256);
+        }
+    }
+}
+
+fn main() {}

crates/sol-types/tests/ui/collisions.stderr

@@ -0,0 +1,35 @@
+error: function selector `0xa9059cbb` collides with `func_2093253501`
+  --> tests/ui/collisions.rs:10:14
+   |
+10 |     function transfer(address,uint256);
+   |              ^^^^^^^^
+   |
+note: other declaration is here
+  --> tests/ui/collisions.rs:9:14
+   |
+9  |     function func_2093253501(bytes);
+   |              ^^^^^^^^^^^^^^^
+
+error: error selector `0x00000000` is reserved
+  --> tests/ui/collisions.rs:12:11
+   |
+12 |     error BlazingIt4490597615();
+   |           ^^^^^^^^^^^^^^^^^^^
+
+error: function selector `0xa9059cbb` collides with `func_2093253501`
+  --> tests/ui/collisions.rs:19:18
+   |
+19 |         function transfer(address,uint256);
+   |                  ^^^^^^^^
+   |
+note: other declaration is here
+  --> tests/ui/collisions.rs:18:18
+   |
+18 |         function func_2093253501(bytes);
+   |                  ^^^^^^^^^^^^^^^
+
+error: error selector `0x00000000` is reserved
+  --> tests/ui/collisions.rs:21:15
+   |
+21 |         error BlazingIt4490597615();
+   |               ^^^^^^^^^^^^^^^^^^^