Add i256 type (#42)

Author: smiasojed

CLAUDE.md

@@ -137,7 +137,7 @@ pub trait StaticEncodedLen: SolEncode {
 | `uint8`..`uint128` | `u8`..`u128` | yes | yes | `impl_static_type!` | |
 | `uint256` | `U256` (ruint) | yes | yes | `impl_static_type!` | |
 | `int8`..`int128` | `i8`..`i128` | yes | yes | `impl_static_type!` | Sign-extended encoding |
-| `int256` | `I256` | **no** | **no** | **missing** | Macro codegen references `I256` but type doesn't exist |
+| `int256` | `I256` | yes | yes | `impl_static_type!` | Newtype around `U256` with two's-complement signed ops |
 | `bool` | `bool` | yes | yes | `impl_static_type!` | |
 | `address` | `Address` | yes | yes | `impl_static_type!` | Wrapper around `[u8; 20]` |
 | `bytesN` | `[u8; N]` | yes | yes | blanket impl | SOL_NAME = `"bytesN"`, left-aligned encoding |
@@ -159,7 +159,6 @@ The `SolArrayElement` marker trait controls which types can be used as elements
 
 ### Known Gaps
 
-- **`I256`**: The decode codegen (`decode.rs`) emits `::pvm_contract_types::I256::from_be_slice(...)` for `Int(256)`, but `I256` is never defined. Any contract using `int256` will fail to compile.
 - **`&[u8]`**: No trait impl for byte slices. The macro compensates with inline codegen for no-alloc `bytes` decoding.
 
 ### Custom Types via `#[derive(SolType)]`

crates/pvm-contract-macros/src/lib.rs

@@ -646,6 +646,7 @@ pub fn fallback(_attr: TokenStream, item: TokenStream) -> TokenStream {
 /// | `u32` | `uint32` | 32 bytes |
 /// | `u16` | `uint16` | 32 bytes |
 /// | `u8` | `uint8` | 32 bytes |
+/// | `I256` | `int256` | 32 bytes |
 /// | `i128` | `int128` | 32 bytes |
 /// | `i64` | `int64` | 32 bytes |
 /// | `i32` | `int32` | 32 bytes |

crates/pvm-contract-macros/src/signature/types.rs

@@ -135,6 +135,10 @@ impl SolType {
             | "::pvm_contract::Address" => Some(SolType::Address),
             "U256" | "ruint::aliases::U256" => Some(SolType::Uint(256)),
             "u256" => Some(SolType::Uint(256)),
+            "I256" | "pvm_contract_types::I256" | "::pvm_contract_types::I256" => {
+                Some(SolType::Int(256))
+            }
+            "i256" => Some(SolType::Int(256)),
             "u128" => Some(SolType::Uint(128)),
             "u64" => Some(SolType::Uint(64)),
             "u32" => Some(SolType::Uint(32)),
@@ -318,6 +322,14 @@ mod tests {
         let ty: syn::Type = syn::parse_str("i128").unwrap();
         let sol = SolType::from_rust_type(&ty).unwrap();
         assert_eq!(sol, SolType::Int(128));
+
+        let ty: syn::Type = syn::parse_str("I256").unwrap();
+        let sol = SolType::from_rust_type(&ty).unwrap();
+        assert_eq!(sol, SolType::Int(256));
+
+        let ty: syn::Type = syn::parse_str("pvm_contract_types::I256").unwrap();
+        let sol = SolType::from_rust_type(&ty).unwrap();
+        assert_eq!(sol, SolType::Int(256));
     }
 
     #[test]

crates/pvm-contract-types/proptest-regressions/tests.txt

@@ -5,3 +5,4 @@
 # It is recommended to check this file in to source control so that
 # everyone who runs the test benefits from these saved cases.
 cc b3613914836697ae21ef98e5dbf2bec0023fb909cb99621462a513a3446024c4 # shrinks to x = 0, y = 0, name = ""
+cc 7189bd9b310d2762ea2ecd592d0e1bb466bf7cd19ee8df563f8536c0580675a3 # shrinks to a_limbs = [0, 0, 0, 9223372036854775808], shift = 1