lang: Added generic support to Accounts (#496)

CHANGELOG.md

@@ -17,6 +17,7 @@ incremented for features.
 
 * lang: Add fallback functions ([#457](https://github.com/project-serum/anchor/pull/457)).
 * lang: Add feature flag for using the old state account discriminator. This is a temporary flag for those with programs built prior to v0.7.0 but want to use the latest Anchor version. Expect this to be removed in a future version ([#446](https://github.com/project-serum/anchor/pull/446)).
+* lang: Add generic support to Accounts ([#496](https://github.com/project-serum/anchor/pull/496)).
 
 ### Breaking Changes
 

lang/attribute/account/src/lib.rs

@@ -78,6 +78,7 @@ pub fn account(
 
     let account_strct = parse_macro_input!(input as syn::ItemStruct);
     let account_name = &account_strct.ident;
+    let (impl_gen, type_gen, where_clause) = account_strct.generics.split_for_impl();
 
     let discriminator: proc_macro2::TokenStream = {
         // Namespace the discriminator to prevent collisions.
@@ -103,12 +104,16 @@ pub fn account(
                 #[zero_copy]
                 #account_strct
 
-                unsafe impl anchor_lang::__private::bytemuck::Pod for #account_name {}
-                unsafe impl anchor_lang::__private::bytemuck::Zeroable for #account_name {}
+                #[automatically_derived]
+                unsafe impl #impl_gen anchor_lang::__private::bytemuck::Pod for #account_name #type_gen #where_clause {}
+                #[automatically_derived]
+                unsafe impl #impl_gen anchor_lang::__private::bytemuck::Zeroable for #account_name #type_gen #where_clause {}
 
-                impl anchor_lang::ZeroCopy for #account_name {}
+                #[automatically_derived]
+                impl #impl_gen anchor_lang::ZeroCopy for #account_name #type_gen #where_clause {}
 
-                impl anchor_lang::Discriminator for #account_name {
+                #[automatically_derived]
+                impl #impl_gen anchor_lang::Discriminator for #account_name #type_gen #where_clause {
                     fn discriminator() -> [u8; 8] {
                         #discriminator
                     }
@@ -116,7 +121,8 @@ pub fn account(
 
                 // This trait is useful for clients deserializing accounts.
                 // It's expected on-chain programs deserialize via zero-copy.
-                impl anchor_lang::AccountDeserialize for #account_name {
+                #[automatically_derived]
+                impl #impl_gen anchor_lang::AccountDeserialize for #account_name #type_gen #where_clause {
                     fn try_deserialize(buf: &mut &[u8]) -> std::result::Result<Self, ProgramError> {
                         if buf.len() < #discriminator.len() {
                             return Err(anchor_lang::__private::ErrorCode::AccountDiscriminatorNotFound.into());
@@ -142,7 +148,8 @@ pub fn account(
                 #[derive(AnchorSerialize, AnchorDeserialize, Clone)]
                 #account_strct
 
-                impl anchor_lang::AccountSerialize for #account_name {
+                #[automatically_derived]
+                impl #impl_gen anchor_lang::AccountSerialize for #account_name #type_gen #where_clause {
                     fn try_serialize<W: std::io::Write>(&self, writer: &mut W) -> std::result::Result<(), ProgramError> {
                         writer.write_all(&#discriminator).map_err(|_| anchor_lang::__private::ErrorCode::AccountDidNotSerialize)?;
                         AnchorSerialize::serialize(
@@ -154,7 +161,8 @@ pub fn account(
                     }
                 }
 
-                impl anchor_lang::AccountDeserialize for #account_name {
+                #[automatically_derived]
+                impl #impl_gen anchor_lang::AccountDeserialize for #account_name #type_gen #where_clause {
                     fn try_deserialize(buf: &mut &[u8]) -> std::result::Result<Self, ProgramError> {
                         if buf.len() < #discriminator.len() {
                             return Err(anchor_lang::__private::ErrorCode::AccountDiscriminatorNotFound.into());
@@ -173,7 +181,8 @@ pub fn account(
                     }
                 }
 
-                impl anchor_lang::Discriminator for #account_name {
+                #[automatically_derived]
+                impl #impl_gen anchor_lang::Discriminator for #account_name #type_gen #where_clause {
                     fn discriminator() -> [u8; 8] {
                         #discriminator
                     }
@@ -206,6 +215,7 @@ pub fn associated(
 ) -> proc_macro::TokenStream {
     let mut account_strct = parse_macro_input!(input as syn::ItemStruct);
     let account_name = &account_strct.ident;
+    let (impl_gen, ty_gen, where_clause) = account_strct.generics.split_for_impl();
 
     // Add a `__nonce: u8` field to the struct to hold the bump seed for
     // the program dervied address.
@@ -245,7 +255,8 @@ pub fn associated(
         #[anchor_lang::account(#args)]
         #account_strct
 
-        impl anchor_lang::Bump for #account_name {
+        #[automatically_derived]
+        impl #impl_gen anchor_lang::Bump for #account_name #ty_gen #where_clause {
             fn seed(&self) -> u8 {
                 self.__nonce
             }
@@ -257,6 +268,7 @@ pub fn associated(
 pub fn derive_zero_copy_accessor(item: proc_macro::TokenStream) -> proc_macro::TokenStream {
     let account_strct = parse_macro_input!(item as syn::ItemStruct);
     let account_name = &account_strct.ident;
+    let (impl_gen, ty_gen, where_clause) = account_strct.generics.split_for_impl();
 
     let fields = match &account_strct.fields {
         syn::Fields::Named(n) => n,
@@ -300,7 +312,8 @@ pub fn derive_zero_copy_accessor(item: proc_macro::TokenStream) -> proc_macro::T
         })
         .collect();
     proc_macro::TokenStream::from(quote! {
-        impl #account_name {
+        #[automatically_derived]
+        impl #impl_gen #account_name #ty_gen #where_clause {
             #(#methods)*
         }
     })

lang/syn/src/codegen/accounts/__client_accounts.rs

@@ -115,6 +115,7 @@ pub fn generate(accs: &AccountsStruct) -> proc_macro2::TokenStream {
                 #(#account_struct_fields),*
             }
 
+            #[automatically_derived]
             impl anchor_lang::ToAccountMetas for #name {
                 fn to_account_metas(&self, is_signer: Option<bool>) -> Vec<anchor_lang::solana_program::instruction::AccountMeta> {
                     let mut account_metas = vec![];

lang/syn/src/codegen/accounts/constraints.rs

@@ -355,24 +355,24 @@ pub fn generate_constraint_associated_init(
     )
 }
 
-fn parse_ty(f: &Field) -> (&syn::Ident, proc_macro2::TokenStream, bool) {
+fn parse_ty(f: &Field) -> (&syn::TypePath, proc_macro2::TokenStream, bool) {
     match &f.ty {
         Ty::ProgramAccount(ty) => (
-            &ty.account_ident,
+            &ty.account_type_path,
             quote! {
                 anchor_lang::ProgramAccount
             },
             false,
         ),
         Ty::Loader(ty) => (
-            &ty.account_ident,
+            &ty.account_type_path,
             quote! {
                 anchor_lang::Loader
             },
             true,
         ),
         Ty::CpiAccount(ty) => (
-            &ty.account_ident,
+            &ty.account_type_path,
             quote! {
                 anchor_lang::CpiAccount
             },
@@ -617,7 +617,7 @@ pub fn generate_constraint_state(f: &Field, c: &ConstraintState) -> proc_macro2:
     let program_target = c.program_target.clone();
     let ident = &f.ident;
     let account_ty = match &f.ty {
-        Ty::CpiState(ty) => &ty.account_ident,
+        Ty::CpiState(ty) => &ty.account_type_path,
         _ => panic!("Invalid state constraint"),
     };
     quote! {

lang/syn/src/codegen/accounts/exit.rs

@@ -1,11 +1,16 @@
-use crate::codegen::accounts::generics;
+use crate::codegen::accounts::{generics, ParsedGenerics};
 use crate::{AccountField, AccountsStruct};
 use quote::quote;
 
 // Generates the `Exit` trait implementation.
 pub fn generate(accs: &AccountsStruct) -> proc_macro2::TokenStream {
     let name = &accs.ident;
-    let (combined_generics, trait_generics, strct_generics) = generics(accs);
+    let ParsedGenerics {
+        combined_generics,
+        trait_generics,
+        struct_generics,
+        where_clause,
+    } = generics(accs);
 
     let on_save: Vec<proc_macro2::TokenStream> = accs
         .fields
@@ -39,7 +44,8 @@ pub fn generate(accs: &AccountsStruct) -> proc_macro2::TokenStream {
         })
         .collect();
     quote! {
-        impl#combined_generics anchor_lang::AccountsExit#trait_generics for #name#strct_generics {
+        #[automatically_derived]
+        impl<#combined_generics> anchor_lang::AccountsExit<#trait_generics> for #name<#struct_generics> #where_clause{
             fn exit(&self, program_id: &anchor_lang::solana_program::pubkey::Pubkey) -> anchor_lang::solana_program::entrypoint::ProgramResult {
                 #(#on_save)*
                 Ok(())

lang/syn/src/codegen/accounts/mod.rs

@@ -1,5 +1,9 @@
 use crate::AccountsStruct;
 use quote::quote;
+use std::iter;
+use syn::punctuated::Punctuated;
+use syn::{ConstParam, LifetimeDef, Token, TypeParam};
+use syn::{GenericParam, PredicateLifetime, WhereClause, WherePredicate};
 
 mod __client_accounts;
 mod constraints;
@@ -26,18 +30,70 @@ pub fn generate(accs: &AccountsStruct) -> proc_macro2::TokenStream {
     }
 }
 
-fn generics(
-    accs: &AccountsStruct,
-) -> (
-    proc_macro2::TokenStream,
-    proc_macro2::TokenStream,
-    proc_macro2::TokenStream,
-) {
-    match accs.generics.lt_token {
-        None => (quote! {<'info>}, quote! {<'info>}, quote! {}),
-        Some(_) => {
-            let g = &accs.generics;
-            (quote! {#g}, quote! {#g}, quote! {#g})
-        }
+fn generics(accs: &AccountsStruct) -> ParsedGenerics {
+    let trait_lifetime = accs
+        .generics
+        .lifetimes()
+        .next()
+        .cloned()
+        .unwrap_or_else(|| syn::parse_str("'info").expect("Could not parse lifetime"));
+
+    let mut where_clause = accs.generics.where_clause.clone().unwrap_or(WhereClause {
+        where_token: Default::default(),
+        predicates: Default::default(),
+    });
+    for lifetime in accs.generics.lifetimes().map(|def| &def.lifetime) {
+        where_clause
+            .predicates
+            .push(WherePredicate::Lifetime(PredicateLifetime {
+                lifetime: lifetime.clone(),
+                colon_token: Default::default(),
+                bounds: iter::once(trait_lifetime.lifetime.clone()).collect(),
+            }))
+    }
+    let trait_lifetime = GenericParam::Lifetime(trait_lifetime);
+
+    ParsedGenerics {
+        combined_generics: if accs.generics.lifetimes().next().is_some() {
+            accs.generics.params.clone()
+        } else {
+            iter::once(trait_lifetime.clone())
+                .chain(accs.generics.params.clone())
+                .collect()
+        },
+        trait_generics: iter::once(trait_lifetime).collect(),
+        struct_generics: accs
+            .generics
+            .params
+            .clone()
+            .into_iter()
+            .map(|param: GenericParam| match param {
+                GenericParam::Const(ConstParam { ident, .. })
+                | GenericParam::Type(TypeParam { ident, .. }) => GenericParam::Type(TypeParam {
+                    attrs: vec![],
+                    ident,
+                    colon_token: None,
+                    bounds: Default::default(),
+                    eq_token: None,
+                    default: None,
+                }),
+                GenericParam::Lifetime(LifetimeDef { lifetime, .. }) => {
+                    GenericParam::Lifetime(LifetimeDef {
+                        attrs: vec![],
+                        lifetime,
+                        colon_token: None,
+                        bounds: Default::default(),
+                    })
+                }
+            })
+            .collect(),
+        where_clause,
     }
 }
+
+struct ParsedGenerics {
+    pub combined_generics: Punctuated<GenericParam, Token![,]>,
+    pub trait_generics: Punctuated<GenericParam, Token![,]>,
+    pub struct_generics: Punctuated<GenericParam, Token![,]>,
+    pub where_clause: WhereClause,
+}

lang/syn/src/codegen/accounts/to_account_infos.rs

@@ -1,11 +1,16 @@
-use crate::codegen::accounts::generics;
+use crate::codegen::accounts::{generics, ParsedGenerics};
 use crate::{AccountField, AccountsStruct};
 use quote::quote;
 
 // Generates the `ToAccountInfos` trait implementation.
 pub fn generate(accs: &AccountsStruct) -> proc_macro2::TokenStream {
     let name = &accs.ident;
-    let (combined_generics, trait_generics, strct_generics) = generics(accs);
+    let ParsedGenerics {
+        combined_generics,
+        trait_generics,
+        struct_generics,
+        where_clause,
+    } = generics(accs);
 
     let to_acc_infos: Vec<proc_macro2::TokenStream> = accs
         .fields
@@ -21,7 +26,8 @@ pub fn generate(accs: &AccountsStruct) -> proc_macro2::TokenStream {
         })
         .collect();
     quote! {
-        impl#combined_generics anchor_lang::ToAccountInfos#trait_generics for #name#strct_generics {
+        #[automatically_derived]
+        impl<#combined_generics> anchor_lang::ToAccountInfos<#trait_generics> for #name <#struct_generics> #where_clause{
             fn to_account_infos(&self) -> Vec<anchor_lang::solana_program::account_info::AccountInfo<'info>> {
                 let mut account_infos = vec![];
 

lang/syn/src/codegen/accounts/to_account_metas.rs

@@ -1,11 +1,9 @@
-use crate::codegen::accounts::generics;
 use crate::{AccountField, AccountsStruct};
 use quote::quote;
 
 // Generates the `ToAccountMetas` trait implementation.
 pub fn generate(accs: &AccountsStruct) -> proc_macro2::TokenStream {
     let name = &accs.ident;
-    let (combined_generics, _trait_generics, strct_generics) = generics(accs);
 
     let to_acc_metas: Vec<proc_macro2::TokenStream> = accs
         .fields
@@ -26,8 +24,12 @@ pub fn generate(accs: &AccountsStruct) -> proc_macro2::TokenStream {
             }
         })
         .collect();
+
+    let (impl_gen, ty_gen, where_clause) = accs.generics.split_for_impl();
+
     quote! {
-        impl#combined_generics anchor_lang::ToAccountMetas for #name#strct_generics {
+        #[automatically_derived]
+        impl#impl_gen anchor_lang::ToAccountMetas for #name #ty_gen #where_clause{
             fn to_account_metas(&self, is_signer: Option<bool>) -> Vec<anchor_lang::solana_program::instruction::AccountMeta> {
                 let mut account_metas = vec![];
 

lang/syn/src/codegen/accounts/try_accounts.rs

@@ -1,4 +1,4 @@
-use crate::codegen::accounts::{constraints, generics};
+use crate::codegen::accounts::{constraints, generics, ParsedGenerics};
 use crate::{AccountField, AccountsStruct, Field, SysvarTy, Ty};
 use proc_macro2::TokenStream;
 use quote::quote;
@@ -7,7 +7,12 @@ use syn::Expr;
 // Generates the `Accounts` trait implementation.
 pub fn generate(accs: &AccountsStruct) -> proc_macro2::TokenStream {
     let name = &accs.ident;
-    let (combined_generics, trait_generics, strct_generics) = generics(accs);
+    let ParsedGenerics {
+        combined_generics,
+        trait_generics,
+        struct_generics,
+        where_clause,
+    } = generics(accs);
 
     // Deserialization for each field
     let deser_fields: Vec<proc_macro2::TokenStream> = accs
@@ -88,7 +93,8 @@ pub fn generate(accs: &AccountsStruct) -> proc_macro2::TokenStream {
     };
 
     quote! {
-        impl#combined_generics anchor_lang::Accounts#trait_generics for #name#strct_generics {
+        #[automatically_derived]
+        impl<#combined_generics> anchor_lang::Accounts<#trait_generics> for #name<#struct_generics> #where_clause {
             #[inline(never)]
             fn try_accounts(
                 program_id: &anchor_lang::solana_program::pubkey::Pubkey,
@@ -133,31 +139,31 @@ fn typed_ident(field: &Field) -> TokenStream {
     let ty = match &field.ty {
         Ty::AccountInfo => quote! { AccountInfo },
         Ty::ProgramState(ty) => {
-            let account = &ty.account_ident;
+            let account = &ty.account_type_path;
             quote! {
                 ProgramState<#account>
             }
         }
         Ty::CpiState(ty) => {
-            let account = &ty.account_ident;
+            let account = &ty.account_type_path;
             quote! {
                 CpiState<#account>
             }
         }
         Ty::ProgramAccount(ty) => {
-            let account = &ty.account_ident;
+            let account = &ty.account_type_path;
             quote! {
                 ProgramAccount<#account>
             }
         }
         Ty::Loader(ty) => {
-            let account = &ty.account_ident;
+            let account = &ty.account_type_path;
             quote! {
                 Loader<#account>
             }
         }
         Ty::CpiAccount(ty) => {
-            let account = &ty.account_ident;
+            let account = &ty.account_type_path;
             quote! {
                 CpiAccount<#account>
             }

lang/syn/src/lib.rs

@@ -12,7 +12,7 @@ use syn::spanned::Spanned;
 use syn::token::Comma;
 use syn::{
     Expr, Generics, Ident, ImplItemMethod, ItemEnum, ItemFn, ItemImpl, ItemMod, ItemStruct, LitInt,
-    LitStr, PatType, Token,
+    LitStr, PatType, Token, TypePath,
 };
 
 pub mod codegen;
@@ -198,30 +198,30 @@ pub enum SysvarTy {
 
 #[derive(Debug, PartialEq)]
 pub struct ProgramStateTy {
-    pub account_ident: Ident,
+    pub account_type_path: TypePath,
 }
 
 #[derive(Debug, PartialEq)]
 pub struct CpiStateTy {
-    pub account_ident: Ident,
+    pub account_type_path: TypePath,
 }
 
 #[derive(Debug, PartialEq)]
 pub struct ProgramAccountTy {
     // The struct type of the account.
-    pub account_ident: Ident,
+    pub account_type_path: TypePath,
 }
 
 #[derive(Debug, PartialEq)]
 pub struct CpiAccountTy {
     // The struct type of the account.
-    pub account_ident: Ident,
+    pub account_type_path: TypePath,
 }
 
 #[derive(Debug, PartialEq)]
 pub struct LoaderTy {
     // The struct type of the account.
-    pub account_ident: Ident,
+    pub account_type_path: TypePath,
 }
 
 #[derive(Debug)]

lang/syn/src/parser/accounts/mod.rs

@@ -118,30 +118,40 @@ fn ident_string(f: &syn::Field) -> ParseResult<String> {
 
 fn parse_program_state(path: &syn::Path) -> ParseResult<ProgramStateTy> {
     let account_ident = parse_account(path)?;
-    Ok(ProgramStateTy { account_ident })
+    Ok(ProgramStateTy {
+        account_type_path: account_ident,
+    })
 }
 
 fn parse_cpi_state(path: &syn::Path) -> ParseResult<CpiStateTy> {
     let account_ident = parse_account(path)?;
-    Ok(CpiStateTy { account_ident })
+    Ok(CpiStateTy {
+        account_type_path: account_ident,
+    })
 }
 
 fn parse_cpi_account(path: &syn::Path) -> ParseResult<CpiAccountTy> {
     let account_ident = parse_account(path)?;
-    Ok(CpiAccountTy { account_ident })
+    Ok(CpiAccountTy {
+        account_type_path: account_ident,
+    })
 }
 
 fn parse_program_account(path: &syn::Path) -> ParseResult<ProgramAccountTy> {
     let account_ident = parse_account(path)?;
-    Ok(ProgramAccountTy { account_ident })
+    Ok(ProgramAccountTy {
+        account_type_path: account_ident,
+    })
 }
 
 fn parse_program_account_zero_copy(path: &syn::Path) -> ParseResult<LoaderTy> {
     let account_ident = parse_account(path)?;
-    Ok(LoaderTy { account_ident })
+    Ok(LoaderTy {
+        account_type_path: account_ident,
+    })
 }
 
-fn parse_account(path: &syn::Path) -> ParseResult<syn::Ident> {
+fn parse_account(path: &syn::Path) -> ParseResult<syn::TypePath> {
     let segments = &path.segments[0];
     match &segments.arguments {
         syn::PathArguments::AngleBracketed(args) => {
@@ -153,18 +163,7 @@ fn parse_account(path: &syn::Path) -> ParseResult<syn::Ident> {
                 ));
             }
             match &args.args[1] {
-                syn::GenericArgument::Type(syn::Type::Path(ty_path)) => {
-                    // TODO: allow segmented paths.
-                    if ty_path.path.segments.len() != 1 {
-                        return Err(ParseError::new(
-                            ty_path.path.span(),
-                            "segmented paths are not currently allowed",
-                        ));
-                    }
-
-                    let path_segment = &ty_path.path.segments[0];
-                    Ok(path_segment.ident.clone())
-                }
+                syn::GenericArgument::Type(syn::Type::Path(ty_path)) => Ok(ty_path.clone()),
                 _ => Err(ParseError::new(
                     args.args[1].span(),
                     "first bracket argument must be a lifetime",

lang/tests/generics_test.rs

@@ -0,0 +1,44 @@
+#![allow(dead_code)]
+
+use anchor_lang::prelude::borsh::maybestd::io::Write;
+use anchor_lang::prelude::*;
+use borsh::{BorshDeserialize, BorshSerialize};
+
+#[derive(Accounts)]
+pub struct GenericsTest<'info, T, U, const N: usize>
+where
+    T: AccountSerialize + AccountDeserialize + Clone,
+    U: BorshSerialize + BorshDeserialize + Default + Clone,
+{
+    pub non_generic: AccountInfo<'info>,
+    pub generic: ProgramAccount<'info, T>,
+    pub const_generic: Loader<'info, Account<N>>,
+    pub associated: CpiAccount<'info, Associated<U>>,
+}
+
+#[account(zero_copy)]
+pub struct Account<const N: usize> {
+    pub data: WrappedU8Array<N>,
+}
+
+#[associated]
+#[derive(Default)]
+pub struct Associated<T>
+where
+    T: BorshDeserialize + BorshSerialize + Default,
+{
+    pub data: T,
+}
+
+#[derive(Copy, Clone)]
+pub struct WrappedU8Array<const N: usize>(u8);
+impl<const N: usize> BorshSerialize for WrappedU8Array<N> {
+    fn serialize<W: Write>(&self, _writer: &mut W) -> borsh::maybestd::io::Result<()> {
+        todo!()
+    }
+}
+impl<const N: usize> BorshDeserialize for WrappedU8Array<N> {
+    fn deserialize(_buf: &mut &[u8]) -> borsh::maybestd::io::Result<Self> {
+        todo!()
+    }
+}