lang/syn: Simplify accounts parsing

lang/syn/src/codegen/accounts.rs

@@ -322,11 +322,8 @@ pub fn generate_constraint_belongs_to(
     f: &Field,
     c: &ConstraintBelongsTo,
 ) -> proc_macro2::TokenStream {
-    // todo: assert the field type.
-
     let target = c.join_target.clone();
     let ident = &f.ident;
-    // todo: would be nice if target could be an account info object.
     quote! {
         if &#ident.#target != #target.to_account_info().key {
             return Err(anchor_lang::solana_program::program_error::ProgramError::Custom(1)); // todo: error codes

lang/syn/src/hash.rs

@@ -78,21 +78,6 @@ impl Hash {
         Hash(<[u8; HASH_BYTES]>::try_from(hash_slice).unwrap())
     }
 
-    pub const fn new_from_array(hash_array: [u8; HASH_BYTES]) -> Self {
-        Self(hash_array)
-    }
-
-    /// unique Hash for tests and benchmarks.
-    pub fn new_unique() -> Self {
-        use std::sync::atomic::{AtomicU64, Ordering};
-        static I: AtomicU64 = AtomicU64::new(1);
-
-        let mut b = [0u8; HASH_BYTES];
-        let i = I.fetch_add(1, Ordering::Relaxed);
-        b[0..8].copy_from_slice(&i.to_le_bytes());
-        Self::new(&b)
-    }
-
     pub fn to_bytes(self) -> [u8; HASH_BYTES] {
         self.0
     }
@@ -130,10 +115,3 @@ pub fn hashv(vals: &[&[u8]]) -> Hash {
 pub fn hash(val: &[u8]) -> Hash {
     hashv(&[val])
 }
-
-/// Return the hash of the given hash extended with the given value.
-pub fn extend_and_hash(id: &Hash, val: &[u8]) -> Hash {
-    let mut hash_data = id.as_ref().to_vec();
-    hash_data.extend_from_slice(val);
-    hash(&hash_data)
-}

lang/syn/src/parser/accounts.rs

@@ -6,15 +6,18 @@ use crate::{
 
 pub fn parse(strct: &syn::ItemStruct) -> AccountsStruct {
     let fields = match &strct.fields {
-        syn::Fields::Named(fields) => fields,
+        syn::Fields::Named(fields) => fields.named.iter().map(parse_account_field).collect(),
         _ => panic!("invalid input"),
     };
+    AccountsStruct::new(strct.clone(), fields)
+}
 
-    let fields: Vec<AccountField> = fields
-        .named
-        .iter()
-        .map(|f: &syn::Field| {
-            let anchor_attr = {
+fn parse_account_field(f: &syn::Field) -> AccountField {
+    let anchor_attr = parse_account_attr(f);
+    parse_field(f, anchor_attr)
+}
+
+fn parse_account_attr(f: &syn::Field) -> Option<&syn::Attribute> {
     let anchor_attrs: Vec<&syn::Attribute> = f
         .attrs
         .iter()
@@ -31,14 +34,8 @@ pub fn parse(strct: &syn::ItemStruct) -> AccountsStruct {
     match anchor_attrs.len() {
         0 => None,
         1 => Some(anchor_attrs[0]),
-                    _ => panic!("invalid syntax: only one account attribute is allowed"),
+        _ => panic!("Invalid syntax: please specify one account attribute."),
     }
-            };
-            parse_field(f, anchor_attr)
-        })
-        .collect();
-
-    AccountsStruct::new(strct.clone(), fields)
 }
 
 fn parse_field(f: &syn::Field, anchor: Option<&syn::Attribute>) -> AccountField {