Allow revert with custom error

Closes ethereum#75

analyzer/src/namespace/types.rs

@@ -220,6 +220,11 @@ impl Struct {
             .map(|(_, typ)| typ)
     }
 
+    /// Return the types of all fields
+    pub fn get_field_types(&self) -> Vec<FixedSize> {
+        self.fields.iter().cloned().map(|(_, typ)| typ).collect()
+    }
+
     /// Return the index of the given field name
     pub fn get_field_index(&self, name: &str) -> Option<usize> {
         self.fields.iter().position(|(field, _)| field == name)

analyzer/src/traversal/functions.rs

@@ -233,7 +233,7 @@ fn func_stmt(
         Assert { .. } => assert(scope, context, stmt),
         Expr { .. } => expr(scope, context, stmt),
         Pass => Ok(()),
-        Revert { .. } => Ok(()),
+        Revert { .. } => revert(scope, context, stmt),
         Break | Continue => {
             loop_flow_statement(scope, context, stmt);
             Ok(())
@@ -439,6 +439,29 @@ fn assert(
     unreachable!()
 }
 
+fn revert(
+    scope: Shared<BlockScope>,
+    context: &mut Context,
+    stmt: &Node<fe::FuncStmt>,
+) -> Result<(), FatalError> {
+    if let fe::FuncStmt::Revert { error } = &stmt.kind {
+        if let Some(error_expr) = error {
+            let error_attributes = expressions::expr(Rc::clone(&scope), context, error_expr, None)?;
+            if !matches!(error_attributes.typ, Type::Struct(_)) {
+                context.error(
+                    "`revert` error must be a struct",
+                    error_expr.span,
+                    format!("this has type `{}`; expected a struct", error_attributes.typ),
+                );
+            }
+        }
+
+        return Ok(());
+    }
+
+    unreachable!()
+}
+
 fn func_return(
     scope: Shared<BlockScope>,
     context: &mut Context,

common/src/utils/abi.rs

@@ -2,16 +2,16 @@ use crate::utils::keccak;
 
 /// Formats the name and fields and calculates the 32 byte keccak256 value of
 /// the signature.
-pub fn event_topic(name: &str, fields: Vec<String>) -> String {
+pub fn event_topic(name: &str, fields: &[String]) -> String {
     sign_event_or_func(name, fields, 32)
 }
 /// Formats the name and params and calculates the 4 byte keccak256 value of the
 /// signature.
-pub fn func_selector(name: &str, params: Vec<String>) -> String {
+pub fn func_selector(name: &str, params: &[String]) -> String {
     sign_event_or_func(name, params, 4)
 }
 
-fn sign_event_or_func(name: &str, params: Vec<String>, size: usize) -> String {
+fn sign_event_or_func(name: &str, params: &[String], size: usize) -> String {
     let signature = format!("{}({})", name, params.join(","));
     keccak::partial(signature.as_bytes(), size)
 }

compiler/src/yul/context.rs

@@ -1,4 +1,5 @@
 use crate::yul::AnalyzerContext;
+use fe_analyzer::namespace::types::{FeString, Struct};
 use indexmap::IndexSet;
 
 // This is contract context, but it's used all over so it has a short name.
@@ -10,6 +11,12 @@ pub struct Context<'a> {
 
     /// Names of contracts that have been created inside of this contract.
     pub created_contracts: IndexSet<String>,
+
+    /// Strings that can be used as revert error in assertions
+    pub assert_strings: IndexSet<FeString>,
+
+    // Structs that can be used as errors in revert statements
+    pub revert_errors: IndexSet<Struct>,
 }
 
 impl<'a> Context<'a> {
@@ -18,6 +25,8 @@ impl<'a> Context<'a> {
             analysis,
             string_literals: IndexSet::new(),
             created_contracts: IndexSet::new(),
+            assert_strings: IndexSet::new(),
+            revert_errors: IndexSet::new(),
         }
     }
 }

compiler/src/yul/mappers/functions.rs

@@ -1,5 +1,8 @@
+use fe_analyzer::namespace::types::FixedSize;
+
 use crate::yul::mappers::{assignments, declarations, expressions};
 use crate::yul::names;
+use crate::yul::operations::abi as abi_operations;
 use crate::yul::operations::data as data_operations;
 use crate::yul::Context;
 use fe_analyzer::context::ExpressionAttributes;
@@ -56,7 +59,7 @@ fn func_stmt(context: &mut Context, stmt: &Node<fe::FuncStmt>) -> yul::Statement
         fe::FuncStmt::Pass => statement! { pop(0) },
         fe::FuncStmt::Break => break_statement(context, stmt),
         fe::FuncStmt::Continue => continue_statement(context, stmt),
-        fe::FuncStmt::Revert { .. } => revert(stmt),
+        fe::FuncStmt::Revert { .. } => revert(context, stmt),
     }
 }
 
@@ -118,8 +121,28 @@ fn expr(context: &mut Context, stmt: &Node<fe::FuncStmt>) -> yul::Statement {
     }
 }
 
-fn revert(stmt: &Node<fe::FuncStmt>) -> yul::Statement {
-    if let fe::FuncStmt::Revert { .. } = &stmt.kind {
+fn revert(context: &mut Context, stmt: &Node<fe::FuncStmt>) -> yul::Statement {
+    if let fe::FuncStmt::Revert { error } = &stmt.kind {
+        if let Some(error_expr) = error {
+            let error_attributes = context
+                .analysis
+                .get_expression(error_expr)
+                .expect("missing expression");
+
+            if let Type::Struct(val) = &error_attributes.typ {
+                context.revert_errors.insert(val.clone());
+
+                let revert_data = expressions::expr(context, error_expr);
+                let size =
+                    abi_operations::encode_size(vec![val.clone()], vec![revert_data.clone()]);
+                let revert_fn = names::revert_name(&val.name, &val.get_field_types());
+
+                return statement! {
+                    ([revert_fn]([revert_data], [size]))
+                };
+            }
+        }
+
         return statement! { revert(0, 0) };
     }
 
@@ -150,7 +173,24 @@ fn assert(context: &mut Context, stmt: &Node<fe::FuncStmt>) -> yul::Statement {
         return match msg {
             Some(val) => {
                 let msg = expressions::expr(context, val);
-                statement! { if (iszero([test])) { (revert_with_reason_string([msg])) } }
+                let msg_expr = context
+                    .analysis
+                    .get_expression(val)
+                    .expect("missing expression");
+
+                if let Type::String(str) = &msg_expr.typ {
+                    let size = abi_operations::encode_size(vec![str.clone()], vec![msg.clone()]);
+                    let fixed_size = FixedSize::String(str.clone());
+                    context.assert_strings.insert(str.clone());
+                    let revert_fn = names::error_revert_name(&[fixed_size]);
+
+                    return statement! {
+                        if (iszero([test])) {
+                            ([revert_fn]([msg], [size]))
+                        }
+                    };
+                }
+                unreachable!()
             }
             None => statement! { if (iszero([test])) { (revert(0, 0)) } },
         };

compiler/src/yul/names.rs

@@ -1,4 +1,5 @@
 use fe_analyzer::namespace::types::{AbiDecodeLocation, AbiEncoding, Integer};
+use fe_common::utils::abi as abi_utils;
 use yultsur::*;
 
 /// Generate a function name to perform checked addition
@@ -59,6 +60,30 @@ pub fn var_name(name: &str) -> yul::Identifier {
     identifier! { (format!("${}", name)) }
 }
 
+/// Generate a revert function name for the name `Error` and a given set of types
+pub fn error_revert_name<T: AbiEncoding>(types: &[T]) -> yul::Identifier {
+    revert_name("Error", types)
+}
+
+/// Generates a revert function name for a given name and types
+pub fn revert_name<T: AbiEncoding>(name: &str, types: &[T]) -> yul::Identifier {
+    let type_names = types
+        .iter()
+        .map(|param| param.lower_snake())
+        .collect::<Vec<String>>();
+
+    let abi_names = types
+        .iter()
+        .map(|param| param.abi_selector_name())
+        .collect::<Vec<String>>();
+
+    let selector = abi_utils::func_selector(name, &abi_names);
+
+    let name = format!("revert_with_{}_{}", selector, &type_names.join("_"));
+
+    identifier! { (name) }
+}
+
 /// Generates an ABI encoding function name for a given set of types.
 pub fn encode_name<T: AbiEncoding>(types: &[T]) -> yul::Identifier {
     let type_names = types

compiler/src/yul/runtime/abi_dispatcher.rs

@@ -58,7 +58,7 @@ fn selector(name: &str, params: &[FixedSize]) -> yul::Literal {
         .map(|param| param.abi_selector_name())
         .collect::<Vec<String>>();
 
-    literal! {(abi_utils::func_selector(name, params))}
+    literal! {(abi_utils::func_selector(name, &params))}
 }
 
 fn selection(name: &str, params: &[FixedSize]) -> yul::Expression {

compiler/src/yul/runtime/functions/contracts.rs

@@ -39,7 +39,7 @@ pub fn calls(contract: Contract) -> Vec<yul::Statement> {
                 .unzip();
             // the function selector must be added to the first 4 bytes of the calldata
             let selector = {
-                let selector = abi_utils::func_selector(&function.name, param_names);
+                let selector = abi_utils::func_selector(&function.name, &param_names);
                 literal_expression! { (selector) }
             };
             // the operations used to encode the parameters

compiler/src/yul/runtime/functions/data.rs

@@ -21,7 +21,6 @@ pub fn all() -> Vec<yul::Statement> {
         mcopys(),
         mloadn(),
         mstoren(),
-        revert_with_reason_string(),
         scopym(),
         scopys(),
         set_zero(),
@@ -381,28 +380,3 @@ pub fn load_data_string() -> yul::Statement {
         }
     }
 }
-
-/// Revert with encoded reason string
-pub fn revert_with_reason_string() -> yul::Statement {
-    function_definition! {
-        function revert_with_reason_string(reason) {
-            // Function selector for Error(string)
-            (let ptr := alloc_mstoren(0x08C379A0, 4))
-
-            // Write the (fixed) data offset into the next 32 bytes of memory
-            (pop((alloc_mstoren(0x0000000000000000000000000000000000000000000000000000000000000020, 32))))
-
-            // Read the size of the string
-            (let reason_size := mloadn(reason, 32))
-
-            //Copy the whole reason string (length + data) to the current segment of memory
-            (pop((mcopym(reason , (add(reason_size, 32))))))
-
-            // Right pad the reason bytes to a multiple of 32 bytes
-            (let padding := sub((ceil32(reason_size)), reason_size))
-            (pop((alloc(padding))))
-
-            (revert(ptr, (add(68, (add(reason_size, padding))))))
-        }
-    }
-}

compiler/src/yul/runtime/functions/mod.rs

@@ -4,6 +4,7 @@ pub mod abi;
 pub mod contracts;
 pub mod data;
 pub mod math;
+pub mod revert;
 pub mod structs;
 
 /// Returns all functions that should be available during runtime.

compiler/src/yul/runtime/functions/revert.rs

@@ -0,0 +1,49 @@
+use crate::yul::names;
+use fe_analyzer::namespace::types::Struct;
+use fe_analyzer::namespace::types::{AbiEncoding, FixedSize};
+use fe_common::utils::abi as abi_utils;
+use yultsur::*;
+
+fn selector(name: &str, params: &[FixedSize]) -> yul::Expression {
+    let params = params
+        .iter()
+        .map(|param| param.abi_selector_name())
+        .collect::<Vec<String>>();
+
+    literal_expression! {(abi_utils::func_selector(name, &params))}
+}
+
+/// Generate a YUL function to revert with the `Error` signature and the
+/// given set of params.
+/// NOTE: This is currently used for `assert False, "message"` statements which are
+/// encoded as `Error(msg="message")`. This will be removed in the future.
+pub fn generate_revert_fn_for_assert(params: &[FixedSize]) -> yul::Statement {
+    generate_revert_fn("Error", params, params)
+}
+
+/// Generate a YUL function to revert with a specific struct used as error data
+pub fn generate_struct_revert(val: &Struct) -> yul::Statement {
+    let struct_fields = val.get_field_types();
+    generate_revert_fn(&val.name, &[FixedSize::Struct(val.clone())], &struct_fields)
+}
+
+/// Generate a YUL function that can be used to revert with data
+pub fn generate_revert_fn(
+    name: &str,
+    encoding_params: &[FixedSize],
+    selector_params: &[FixedSize],
+) -> yul::Statement {
+    let abi_encode_fn = names::encode_name(encoding_params);
+
+    let function_name = names::revert_name(name, selector_params);
+
+    let selector = selector(name, &selector_params);
+
+    return function_definition! {
+        function [function_name](data_ptr, size) {
+            (let ptr := alloc_mstoren([selector], 4))
+            (pop(([abi_encode_fn](data_ptr))))
+            (revert(ptr, (add(4, size))))
+        }
+    };
+}

compiler/src/yul/runtime/mod.rs

@@ -35,6 +35,20 @@ pub fn build(context: &Context, contract: &Node<fe::Contract>) -> Vec<yul::State
                 .map(|function| function.param_types())
                 .collect();
 
+            let assert_strings_batch = context
+                .assert_strings
+                .clone()
+                .into_iter()
+                .map(|val| vec![val.into()])
+                .collect::<Vec<_>>();
+
+            let revert_errors_batch = context
+                .revert_errors
+                .clone()
+                .into_iter()
+                .map(|val| val.get_field_types())
+                .collect::<Vec<_>>();
+
             let structs_batch = attributes
                 .structs
                 .clone()
@@ -46,6 +60,8 @@ pub fn build(context: &Context, contract: &Node<fe::Contract>) -> Vec<yul::State
                 public_functions_batch,
                 events_batch,
                 contracts_batch,
+                assert_strings_batch,
+                revert_errors_batch,
                 structs_batch,
             ]
             .concat();
@@ -99,7 +115,30 @@ pub fn build(context: &Context, contract: &Node<fe::Contract>) -> Vec<yul::State
             .collect::<Vec<_>>()
             .concat();
 
-        return [std, encoding, decoding, contract_calls, struct_apis].concat();
+        let revert_calls_from_assert = context
+            .assert_strings
+            .clone()
+            .into_iter()
+            .map(|val| functions::revert::generate_revert_fn_for_assert(&[val.into()]))
+            .collect::<Vec<_>>();
+
+        let revert_calls = context
+            .revert_errors
+            .clone()
+            .into_iter()
+            .map(|val| functions::revert::generate_struct_revert(&val))
+            .collect::<Vec<_>>();
+
+        return [
+            std,
+            encoding,
+            decoding,
+            contract_calls,
+            revert_calls_from_assert,
+            revert_calls,
+            struct_apis,
+        ]
+        .concat();
     }
 
     panic!("missing contract attributes")

newsfragments/464.feature.md

@@ -0,0 +1,13 @@
+Revert with custom errors
+
+Example:
+
+```
+struct PlatformError:
+  code: u256
+
+pub def do_something():
+  revert PlatformError(code=4711)
+```
+
+Error encoding [follows Solidity](https://docs.soliditylang.org/en/v0.8.4/abi-spec.html#errors) which is based on [EIP-838](https://github.com/ethereum/EIPs/issues/838). This means that custom errors returned from Fe are fully compatible with Solidity.