Merge #845: various improvements/refactors of the decoder and its errors

cdb36c1 miniscript: rename parse_* functions to decode_* (Andrew Poelstra)
5fea2b3 miniscript: rename and cleanup decode::KeyParseError (Andrew Poelstra)
a57fab3 miniscript: replace many calls to reduce0 in decode with infallible constructors (Andrew Poelstra)
5b736bd miniscript: move lexer errors into their own type (Andrew Poelstra)
ceadd0d miniscript: use byte arrays in lexer (Andrew Poelstra)

Pull request description:

  The last commit, which renames `parse_with_ext` to `decode_with_ext`, I think we should backport with deprecation to 12.x. This is a pretty uncommonly used function and is unlikely to bother anybody, but the current name is inconsistent with our general use of "parse" for strings and "decode" for scripts.


ACKs for top commit:
  sanket1729:
    ACK cdb36c1


Tree-SHA512: 8a3563dd23e49cf9331b299e237337a3d1097c15d5fe143ec9aa3f686d681fda077f019b25f0d66fccdd9a88ec489a84e144fcbb28410a671eb113f38e0fe58d

Author: apoelstra

fuzz/fuzz_targets/roundtrip_miniscript_script.rs

@@ -8,7 +8,7 @@ fn do_test(data: &[u8]) {
     // Try round-tripping as a script
     let script = script::Script::from_bytes(data);
 
-    if let Ok(pt) = Miniscript::<miniscript::bitcoin::PublicKey, Segwitv0>::parse(script) {
+    if let Ok(pt) = Miniscript::<miniscript::bitcoin::PublicKey, Segwitv0>::decode(script) {
         let output = pt.encode();
         assert_eq!(pt.script_size(), output.len());
         assert_eq!(&output, script);

fuzz/fuzz_targets/roundtrip_miniscript_script_tap.rs

@@ -8,7 +8,7 @@ fn do_test(data: &[u8]) {
     // Try round-tripping as a script
     let script = script::Script::from_bytes(data);
 
-    if let Ok(pt) = Miniscript::<miniscript::bitcoin::key::XOnlyPublicKey, Tap>::parse(script) {
+    if let Ok(pt) = Miniscript::<miniscript::bitcoin::key::XOnlyPublicKey, Tap>::decode(script) {
         let output = pt.encode();
         assert_eq!(pt.script_size(), output.len());
         assert_eq!(&output, script);

src/interpreter/inner.rs

@@ -43,7 +43,7 @@ fn script_from_stack_elem<Ctx: ScriptContext>(
 ) -> Result<Miniscript<Ctx::Key, Ctx>, Error> {
     match *elem {
         stack::Element::Push(sl) => {
-            Miniscript::parse_with_ext(bitcoin::Script::from_bytes(sl), &ExtParams::allow_all())
+            Miniscript::decode_with_ext(bitcoin::Script::from_bytes(sl), &ExtParams::allow_all())
                 .map_err(Error::from)
         }
         stack::Element::Satisfied => Ok(Miniscript::TRUE),
@@ -327,7 +327,7 @@ pub(super) fn from_txdata<'txin>(
     } else {
         if wit_stack.is_empty() {
             // Bare script parsed in BareCtx
-            let miniscript = Miniscript::<bitcoin::PublicKey, BareCtx>::parse_with_ext(
+            let miniscript = Miniscript::<bitcoin::PublicKey, BareCtx>::decode_with_ext(
                 spk,
                 &ExtParams::allow_all(),
             )?;

src/lib.rs

@@ -131,8 +131,6 @@ mod util;
 use core::{fmt, hash, str};
 
 use bitcoin::hashes::{hash160, ripemd160, sha256, Hash};
-use bitcoin::hex::DisplayHex;
-use bitcoin::{script, Opcode};
 
 pub use crate::blanket_traits::FromStrKey;
 pub use crate::descriptor::{DefiniteDescriptorKey, Descriptor, DescriptorPublicKey};
@@ -436,15 +434,8 @@ pub trait ForEachKey<Pk: MiniscriptKey> {
 
 #[derive(Debug)]
 pub enum Error {
-    /// Opcode appeared which is not part of the script subset
-    InvalidOpcode(Opcode),
-    /// Some opcode occurred followed by `OP_VERIFY` when it had
-    /// a `VERIFY` version that should have been used instead
-    NonMinimalVerify(String),
-    /// Push was illegal in some context
-    InvalidPush(Vec<u8>),
-    /// rust-bitcoin script error
-    Script(script::Error),
+    /// Error when lexing a bitcoin Script.
+    ScriptLexer(crate::miniscript::lex::Error),
     /// rust-bitcoin address error
     AddrError(bitcoin::address::ParseError),
     /// rust-bitcoin p2sh address error
@@ -490,7 +481,7 @@ pub enum Error {
     /// Bare descriptors don't have any addresses
     BareDescriptorAddr,
     /// PubKey invalid under current context
-    PubKeyCtxError(miniscript::decode::KeyParseError, &'static str),
+    PubKeyCtxError(miniscript::decode::KeyError, &'static str),
     /// No script code for Tr descriptors
     TrNoScriptCode,
     /// At least two BIP389 key expressions in the descriptor contain tuples of
@@ -519,12 +510,7 @@ const MAX_RECURSION_DEPTH: u32 = 402;
 impl fmt::Display for Error {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         match *self {
-            Error::InvalidOpcode(op) => write!(f, "invalid opcode {}", op),
-            Error::NonMinimalVerify(ref tok) => write!(f, "{} VERIFY", tok),
-            Error::InvalidPush(ref push) => {
-                write!(f, "invalid push {:x}", push.as_hex())
-            },
-            Error::Script(ref e) => fmt::Display::fmt(e, f),
+            Error::ScriptLexer(ref e) => e.fmt(f),
             Error::AddrError(ref e) => fmt::Display::fmt(e, f),
             Error::AddrP2shError(ref e) => fmt::Display::fmt(e, f),
             Error::UnexpectedStart => f.write_str("unexpected start of script"),
@@ -576,10 +562,7 @@ impl std::error::Error for Error {
         use self::Error::*;
 
         match self {
-            InvalidOpcode(_)
-            | NonMinimalVerify(_)
-            | InvalidPush(_)
-            | UnexpectedStart
+            UnexpectedStart
             | Unexpected(_)
             | UnknownWrapper(_)
             | NonTopLevel(_)
@@ -593,7 +576,7 @@ impl std::error::Error for Error {
             | BareDescriptorAddr
             | TrNoScriptCode
             | MultipathDescLenMismatch => None,
-            Script(e) => Some(e),
+            ScriptLexer(e) => Some(e),
             AddrError(e) => Some(e),
             AddrP2shError(e) => Some(e),
             Secp(e) => Some(e),
@@ -614,6 +597,11 @@ impl std::error::Error for Error {
     }
 }
 
+#[doc(hidden)]
+impl From<miniscript::lex::Error> for Error {
+    fn from(e: miniscript::lex::Error) -> Error { Error::ScriptLexer(e) }
+}
+
 #[doc(hidden)]
 impl From<miniscript::types::Error> for Error {
     fn from(e: miniscript::types::Error) -> Error { Error::TypeCheck(e.to_string()) }

src/miniscript/analyzable.rs

@@ -13,7 +13,7 @@ use crate::prelude::*;
 use crate::{Miniscript, MiniscriptKey, ScriptContext, Terminal};
 
 /// Params for parsing miniscripts that either non-sane or non-specified(experimental) in the spec.
-/// Used as a parameter [`Miniscript::from_str_ext`] and [`Miniscript::parse_with_ext`].
+/// Used as a parameter [`Miniscript::from_str_ext`] and [`Miniscript::decode_with_ext`].
 ///
 /// This allows parsing miniscripts if
 /// 1. It is unsafe(does not require a digital signature to spend it)