bug: unused generic type parameters (#1136)

Unused generic type parameters will now be included as PhantomData in both generated structs and enums.
FuelLabs · Oct 10, 2023 · 91ffd8f · 91ffd8f
1 parent 22f10db
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diff --git a/docs/src/types/custom_types.md b/docs/src/types/custom_types.md
@@ -59,3 +59,45 @@ Your Rust code would look like this:
 ```rust,ignore
 {{#include ../../../packages/fuels/tests/types_contracts.rs:generic}}
 ```
+
+### Unused generic type parameters
+
+Sway supports unused generic type parameters when declaring structs/enums:
+
+```Rust
+struct SomeStruct<T, K> {
+  field: u64
+}
+
+enum SomeEnum<T, K> {
+  One: u64
+}
+
+```
+
+If you tried the same in Rust you'd get complaints that `T` and `K` must be used or removed. When generating Rust bindings for such types we make use of the [`PhantomData`](https://doc.rust-lang.org/std/marker/struct.PhantomData.html#unused-type-parameters) type. The generated bindings for the above example would look something like this:
+
+```Rust
+struct SomeStruct<T, K> {
+   pub field: u64,
+   pub _unused_generic_0: PhantomData<T>
+   pub _unused_generic_1: PhantomData<K>
+}
+
+enum SomeEnum<T, K> {
+  One(u64),
+  IgnoreMe(PhantomData<T>, PhantomData<K>)
+}
+```
+
+To lessen the impact to developer experience you may use `SomeStruct::new` to initialize the above structure without bothering with the `PhantomData`s:
+
+```rust,ignore
+{{#include ../../../examples/types/src/lib.rs:unused_generics_struct}}
+```
+
+If your struct doesn't have any fields we'll also derive `Default`. As for enums all `PhantomData`s are placed inside a new variant called `IgnoreMe` which you'll need to ignore in your matches:
+
+```rust,ignore
+{{#include ../../../examples/types/src/lib.rs:unused_generics_enum}}
+```
diff --git a/examples/types/src/lib.rs b/examples/types/src/lib.rs
@@ -166,4 +166,157 @@ mod tests {
         // ANCHOR_END: type_conversion
         Ok(())
     }
+
+    #[tokio::test]
+    async fn unused_generics() -> Result<()> {
+        use fuels::prelude::*;
+        abigen!(Contract(
+            name = "MyContract",
+            abi = r#" {
+  "types": [
+    {
+      "typeId": 0,
+      "type": "()",
+      "components": [],
+      "typeParameters": null
+    },
+    {
+      "typeId": 1,
+      "type": "enum MyEnum",
+      "components": [
+        {
+          "name": "One",
+          "type": 7,
+          "typeArguments": null
+        }
+      ],
+      "typeParameters": [
+        3,
+        2
+      ]
+    },
+    {
+      "typeId": 2,
+      "type": "generic K",
+      "components": null,
+      "typeParameters": null
+    },
+    {
+      "typeId": 3,
+      "type": "generic T",
+      "components": null,
+      "typeParameters": null
+    },
+    {
+      "typeId": 4,
+      "type": "struct MyStruct",
+      "components": [
+        {
+          "name": "field",
+          "type": 7,
+          "typeArguments": null
+        }
+      ],
+      "typeParameters": [
+        3,
+        2
+      ]
+    },
+    {
+      "typeId": 5,
+      "type": "u16",
+      "components": null,
+      "typeParameters": null
+    },
+    {
+      "typeId": 6,
+      "type": "u32",
+      "components": null,
+      "typeParameters": null
+    },
+    {
+      "typeId": 7,
+      "type": "u64",
+      "components": null,
+      "typeParameters": null
+    },
+    {
+      "typeId": 8,
+      "type": "u8",
+      "components": null,
+      "typeParameters": null
+    }
+  ],
+  "functions": [
+    {
+      "inputs": [
+        {
+          "name": "arg",
+          "type": 4,
+          "typeArguments": [
+            {
+              "name": "",
+              "type": 8,
+              "typeArguments": null
+            },
+            {
+              "name": "",
+              "type": 5,
+              "typeArguments": null
+            }
+          ]
+        },
+        {
+          "name": "arg_2",
+          "type": 1,
+          "typeArguments": [
+            {
+              "name": "",
+              "type": 6,
+              "typeArguments": null
+            },
+            {
+              "name": "",
+              "type": 7,
+              "typeArguments": null
+            }
+          ]
+        }
+      ],
+      "name": "test_function",
+      "output": {
+        "name": "",
+        "type": 0,
+        "typeArguments": null
+      },
+      "attributes": null
+    }
+  ],
+  "loggedTypes": [],
+  "messagesTypes": [],
+  "configurables": []
+}"#
+        ));
+
+        // ANCHOR: unused_generics_struct
+        assert_eq!(
+            <MyStruct<u16, u32>>::new(15),
+            MyStruct {
+                field: 15,
+                _unused_generic_0: std::marker::PhantomData,
+                _unused_generic_1: std::marker::PhantomData
+            }
+        );
+        // ANCHOR_END: unused_generics_struct
+
+        let my_enum = <MyEnum<u32, u64>>::One(15);
+        // ANCHOR: unused_generics_enum
+        match my_enum {
+            MyEnum::One(_value) => {}
+            MyEnum::IgnoreMe(..) => panic!("Will never receive this variant"),
+        }
+        // ANCHOR_END: unused_generics_enum
+
+        Ok(())
+    }
 }
diff --git a/packages/fuels-code-gen/Cargo.toml b/packages/fuels-code-gen/Cargo.toml
@@ -19,5 +19,9 @@ regex = { workspace = true }
 serde_json = { workspace = true }
 syn = { workspace = true }
 
+[dev-dependencies]
+pretty_assertions = "1.4"
+
+
 [package.metadata.cargo-machete]
 ignored = ["Inflector"]
diff --git a/packages/fuels-code-gen/src/program_bindings/abigen/bindings/contract.rs b/packages/fuels-code-gen/src/program_bindings/abigen/bindings/contract.rs
@@ -162,16 +162,21 @@ pub(crate) fn expand_fn(abi_fun: &FullABIFunction) -> Result<TokenStream> {
     };
     generator.set_body(body);
 
-    Ok(generator.into())
+    Ok(generator.generate())
 }
 
 #[cfg(test)]
 mod tests {
     use std::collections::HashMap;
 
-    use fuel_abi_types::abi::program::{ABIFunction, ProgramABI, TypeApplication, TypeDeclaration};
+    use fuel_abi_types::abi::{
+        full_program::FullABIFunction,
+        program::{ABIFunction, ProgramABI, TypeApplication, TypeDeclaration},
+    };
+    use pretty_assertions::assert_eq;
+    use quote::quote;
 
-    use super::*;
+    use crate::{error::Result, program_bindings::abigen::bindings::contract::expand_fn};
 
     #[test]
     fn test_expand_fn_simple_abi() -> Result<()> {
@@ -395,13 +400,13 @@ mod tests {
 
         let expected = quote! {
             #[doc = "Calls the contract's `HelloWorld` function"]
-            pub fn HelloWorld(&self, bimbam: bool) -> ::fuels::programs::contract::ContractCallHandler<T, ()> {
+            pub fn HelloWorld(&self, bimbam: ::core::primitive::bool) -> ::fuels::programs::contract::ContractCallHandler<T, ()> {
                 ::fuels::programs::contract::method_hash(
                     self.contract_id.clone(),
                     self.account.clone(),
                     ::fuels::core::codec::resolve_fn_selector(
                         "HelloWorld",
-                        &[<bool as ::fuels::core::traits::Parameterize>::param_type()]
+                        &[<::core::primitive::bool as ::fuels::core::traits::Parameterize>::param_type()]
                     ),
                     &[::fuels::core::traits::Tokenizable::into_token(bimbam)],
                     self.log_decoder.clone(),