error: remove two more variants which were redundant with threshold errors

Author: apoelstra

src/lib.rs

@@ -423,10 +423,6 @@ pub enum Error {
     AddrError(bitcoin::address::ParseError),
     /// rust-bitcoin p2sh address error
     AddrP2shError(bitcoin::address::P2shError),
-    /// A `CHECKMULTISIG` opcode was preceded by a number > 20
-    CmsTooManyKeys(u32),
-    /// A tapscript multi_a cannot support more than Weight::MAX_BLOCK/32 keys
-    MultiATooManyKeys(u64),
     /// While parsing backward, hit beginning of script
     UnexpectedStart,
     /// Got something we were not expecting
@@ -504,7 +500,6 @@ impl fmt::Display for Error {
             Error::Script(ref e) => fmt::Display::fmt(e, f),
             Error::AddrError(ref e) => fmt::Display::fmt(e, f),
             Error::AddrP2shError(ref e) => fmt::Display::fmt(e, f),
-            Error::CmsTooManyKeys(n) => write!(f, "checkmultisig with {} keys", n),
             Error::UnexpectedStart => f.write_str("unexpected start of script"),
             Error::Unexpected(ref s) => write!(f, "unexpected «{}»", s),
             Error::MultiColon(ref s) => write!(f, "«{}» has multiple instances of «:»", s),
@@ -539,7 +534,6 @@ impl fmt::Display for Error {
             Error::PubKeyCtxError(ref pk, ref ctx) => {
                 write!(f, "Pubkey error: {} under {} scriptcontext", pk, ctx)
             }
-            Error::MultiATooManyKeys(k) => write!(f, "MultiA too many keys {}", k),
             Error::TrNoScriptCode => write!(f, "No script code for Tr descriptors"),
             Error::MultipathDescLenMismatch => write!(f, "At least two BIP389 key expressions in the descriptor contain tuples of derivation indexes of different lengths"),
             Error::AbsoluteLockTime(ref e) => e.fmt(f),
@@ -560,8 +554,6 @@ impl std::error::Error for Error {
             InvalidOpcode(_)
             | NonMinimalVerify(_)
             | InvalidPush(_)
-            | CmsTooManyKeys(_)
-            | MultiATooManyKeys(_)
             | UnexpectedStart
             | Unexpected(_)
             | MultiColon(_)

src/miniscript/decode.rs

@@ -17,6 +17,7 @@ use crate::miniscript::lex::{Token as Tk, TokenIter};
 use crate::miniscript::limits::{MAX_PUBKEYS_IN_CHECKSIGADD, MAX_PUBKEYS_PER_MULTISIG};
 use crate::miniscript::ScriptContext;
 use crate::prelude::*;
+use crate::primitives::threshold;
 #[cfg(doc)]
 use crate::Descriptor;
 use crate::{
@@ -538,10 +539,8 @@ pub fn parse<Ctx: ScriptContext>(
                     },
                     // CHECKMULTISIG based multisig
                     Tk::CheckMultiSig, Tk::Num(n) => {
-                        // Check size before allocating keys
-                        if n as usize > MAX_PUBKEYS_PER_MULTISIG {
-                            return Err(Error::CmsTooManyKeys(n));
-                        }
+                        threshold::validate_k_n::<MAX_PUBKEYS_PER_MULTISIG>(1, n as usize).map_err(Error::Threshold)?;
+
                         let mut keys = Vec::with_capacity(n as usize);
                         for _ in 0..n {
                             match_token!(
@@ -562,11 +561,9 @@ pub fn parse<Ctx: ScriptContext>(
                     },
                     // MultiA
                     Tk::NumEqual, Tk::Num(k) => {
-                        // Check size before allocating keys
-                        if k as usize > MAX_PUBKEYS_IN_CHECKSIGADD {
-                            return Err(Error::MultiATooManyKeys(MAX_PUBKEYS_IN_CHECKSIGADD as u64))
-                        }
-                        let mut keys = Vec::with_capacity(k as usize); // atleast k capacity
+                        threshold::validate_k_n::<MAX_PUBKEYS_IN_CHECKSIGADD>(k as usize, k as usize).map_err(Error::Threshold)?;
+
+                        let mut keys = Vec::with_capacity(k as usize); // at least k capacity
                         while tokens.peek() == Some(&Tk::CheckSigAdd) {
                             match_token!(
                                 tokens,

src/primitives/threshold.rs

@@ -40,6 +40,15 @@ impl std::error::Error for ThresholdError {
     fn source(&self) -> Option<&(dyn std::error::Error + 'static)> { None }
 }
 
+/// Check whether `k` and `n` are valid for an instance of [`Self`].
+pub fn validate_k_n<const MAX: usize>(k: usize, n: usize) -> Result<(), ThresholdError> {
+    if k == 0 || k > n || (MAX > 0 && n > MAX) {
+        Err(ThresholdError { k, n, max: (MAX > 0).then_some(MAX) })
+    } else {
+        Ok(())
+    }
+}
+
 /// Structure representing a k-of-n threshold collection of some arbitrary
 /// object `T`.
 ///
@@ -54,11 +63,8 @@ pub struct Threshold<T, const MAX: usize> {
 impl<T, const MAX: usize> Threshold<T, MAX> {
     /// Constructs a threshold directly from a threshold value and collection.
     pub fn new(k: usize, inner: Vec<T>) -> Result<Self, ThresholdError> {
-        if k == 0 || k > inner.len() || (MAX > 0 && inner.len() > MAX) {
-            Err(ThresholdError { k, n: inner.len(), max: (MAX > 0).then_some(MAX) })
-        } else {
-            Ok(Threshold { k, inner })
-        }
+        validate_k_n::<MAX>(k, inner.len())?;
+        Ok(Threshold { k, inner })
     }
 
     /// Constructs a threshold from a threshold value and an iterator that yields collection