Merge ElementsProject#30: revamp Extension and ExtParam traits

a08a03c msrv fixes (Andrew Poelstra)
9bd330e run cargo fmt (Andrew Poelstra)
928bf29 descriptor: make (almost) all methods generic over the extension type (Andrew Poelstra)
9a4a5a0 rename Transalator to Translator (Andrew Poelstra)
a730990 refactor `Descriptor` to be parameterized by Extension, not ExtParam (Andrew Poelstra)
3c64411 extension: introduce TranslateExtParam trait (Andrew Poelstra)
dd1a688 remove some no-op covenant conversions (Andrew Poelstra)
b3e88cd [MOVE ONLY] covenants: move ExtParams to its own module (Andrew Poelstra)

Pull request description:

  The existing code made `Descriptor` generic over `ExtParam` rather than `Extension`. This made the `Extension` trati basically useless since every `Descriptor` always had `CovenantExt` as its extension type.

  It also caused me a lot of confusion because I tried to call the `address` method on a `Descriptor<Pk, NoExt>`, which I was able to parse, just not call any methods on. I pulled on this string and 1000 lines later here we are.

ACKs for top commit:
  sanket1729:
    code review ACK a08a03c. I am attempting to write an extension for Any prevout and APOAS (any prevout any script) just to see what a downstream implementation of an Extension might look like.

Tree-SHA512: ff15cde3f84606286af0b3ff504fe6b306789d5a95e50b964a3f62c44d70bb9247520fa870b242cbdeab15760a69d998976be85932def074073672601127f822

Author: sanket1729

contrib/test.sh

@@ -4,15 +4,20 @@ set -e
 
 FEATURES="compiler use-serde rand"
 
-# Use toolchain if explicitly specified
-if [ -n "$TOOLCHAIN" ]
-then
-    alias cargo="cargo +$TOOLCHAIN"
-fi
-
 cargo --version
 rustc --version
 
+MSRV=false
+if cargo --version | grep "1\.41\.0"; then
+    MSRV=true
+fi
+
+if [ "$MSRV" = true ]; then
+    cargo update -p url --precise 2.2.2
+    cargo update -p form_urlencoded --precise 1.0.1
+    cargo update -p once_cell --precise 1.13.1
+fi
+
 # Format if told to
 if [ "$DO_FMT" = true ]
 then

fuzz/Cargo.toml

@@ -12,7 +12,7 @@ afl_fuzz = ["afl"]
 honggfuzz_fuzz = ["honggfuzz"]
 
 [dependencies]
-honggfuzz = { version = "0.5", optional = true }
+honggfuzz = { version = "0.5", optional = true, default-features = false }
 afl = { version = "0.8", optional = true }
 regex = { version = "1.4"}
 elements-miniscript = { path = "..", features = ["compiler"] }

fuzz/travis-fuzz.sh

@@ -1,6 +1,6 @@
 #!/bin/bash
 set -e
-cargo install --force honggfuzz
+cargo install --force honggfuzz --no-default-features
 for TARGET in fuzz_targets/*; do
     FILENAME=$(basename $TARGET)
 	FILE="${FILENAME%.*}"

src/descriptor/bare.rs

@@ -25,13 +25,12 @@ use elements::{self, script, secp256k1_zkp, Script};
 use super::checksum::{desc_checksum, verify_checksum};
 use super::ELMTS_STR;
 use crate::expression::{self, FromTree};
-use crate::extensions::ExtParam;
 use crate::miniscript::context::ScriptContext;
 use crate::policy::{semantic, Liftable};
 use crate::util::{varint_len, witness_to_scriptsig};
 use crate::{
-    elementssig_to_rawsig, BareCtx, Error, Extension, ForEach, ForEachKey, Miniscript,
-    MiniscriptKey, Satisfier, ToPublicKey, TranslateExt, TranslatePk, Translator,
+    elementssig_to_rawsig, BareCtx, Error, ForEach, ForEachKey, Miniscript, MiniscriptKey,
+    Satisfier, ToPublicKey, TranslatePk, Translator,
 };
 
 /// Create a Bare Descriptor. That is descriptor that is
@@ -193,24 +192,6 @@ impl<P: MiniscriptKey, Q: MiniscriptKey> TranslatePk<P, Q> for Bare<P> {
     }
 }
 
-impl<PExt, QExt, PArg, QArg, Pk> TranslateExt<PExt, QExt, PArg, QArg> for Bare<Pk>
-where
-    PExt: Extension,
-    QExt: Extension,
-    PArg: ExtParam,
-    QArg: ExtParam,
-    Pk: MiniscriptKey,
-{
-    type Output = Bare<Pk>;
-
-    fn translate_ext<T, E>(&self, _translator: &mut T) -> Result<Self::Output, E>
-    where
-        T: crate::ExtTranslator<PArg, QArg, E>,
-    {
-        Ok(self.clone())
-    }
-}
-
 /// A bare PkH descriptor at top level
 #[derive(Clone, Ord, PartialOrd, Eq, PartialEq, Hash)]
 pub struct Pkh<Pk: MiniscriptKey> {
@@ -376,21 +357,3 @@ impl<P: MiniscriptKey, Q: MiniscriptKey> TranslatePk<P, Q> for Pkh<P> {
         Ok(Pkh::new(t.pk(&self.pk)?))
     }
 }
-
-impl<PExt, QExt, PArg, QArg, Pk> TranslateExt<PExt, QExt, PArg, QArg> for Pkh<Pk>
-where
-    PExt: Extension,
-    QExt: Extension,
-    PArg: ExtParam,
-    QArg: ExtParam,
-    Pk: MiniscriptKey,
-{
-    type Output = Pkh<Pk>;
-
-    fn translate_ext<T, E>(&self, _translator: &mut T) -> Result<Self::Output, E>
-    where
-        T: crate::ExtTranslator<PArg, QArg, E>,
-    {
-        Ok(self.clone())
-    }
-}

src/descriptor/blinded.rs

@@ -25,7 +25,7 @@ use elements::{self, Script};
 use super::checksum::{desc_checksum, strip_checksum, verify_checksum};
 use super::{Descriptor, TranslatePk};
 use crate::expression::{self, FromTree};
-use crate::extensions::CovExtArgs;
+use crate::extensions::{CovExtArgs, CovenantExt};
 use crate::policy::{semantic, Liftable};
 use crate::{Error, MiniscriptKey, Satisfier, ToPublicKey, Translator};
 
@@ -40,12 +40,12 @@ pub struct Blinded<Pk: MiniscriptKey> {
     /// permitted at the root level.
     ///
     /// TODO: Add blinding support to descriptor extensions
-    desc: Descriptor<Pk, CovExtArgs>,
+    desc: Descriptor<Pk, CovenantExt<CovExtArgs>>,
 }
 
 impl<Pk: MiniscriptKey> Blinded<Pk> {
     /// Create a new blinded descriptor from a descriptor and blinder
-    pub fn new(blinder: Pk, desc: Descriptor<Pk, CovExtArgs>) -> Self {
+    pub fn new(blinder: Pk, desc: Descriptor<Pk, CovenantExt<CovExtArgs>>) -> Self {
         Self { blinder, desc }
     }
 
@@ -55,12 +55,12 @@ impl<Pk: MiniscriptKey> Blinded<Pk> {
     }
 
     /// get the unblinded descriptor
-    pub fn as_unblinded(&self) -> &Descriptor<Pk, CovExtArgs> {
+    pub fn as_unblinded(&self) -> &Descriptor<Pk, CovenantExt<CovExtArgs>> {
         &self.desc
     }
 
     /// get the unblinded descriptor
-    pub fn into_unblinded(self) -> Descriptor<Pk, CovExtArgs> {
+    pub fn into_unblinded(self) -> Descriptor<Pk, CovenantExt<CovExtArgs>> {
         self.desc
     }
 }
@@ -92,7 +92,7 @@ impl_from_tree!(
     fn from_tree(top: &expression::Tree<'_>) -> Result<Self, Error> {
         if top.name == "blinded" && top.args.len() == 2 {
             let blinder = expression::terminal(&top.args[0], |pk| Pk::from_str(pk))?;
-            let desc = Descriptor::<Pk, CovExtArgs>::from_tree(&top.args[1])?;
+            let desc = Descriptor::<Pk, CovenantExt<CovExtArgs>>::from_tree(&top.args[1])?;
             if top.args[1].name == "blinded" {
                 return Err(Error::BadDescriptor(
                     "Blinding only permitted at root level".to_string(),

src/descriptor/csfs_cov/cov.rs

@@ -51,7 +51,7 @@ use super::super::checksum::{desc_checksum, verify_checksum};
 use super::super::ELMTS_STR;
 use super::{CovError, CovOperations};
 use crate::expression::{self, FromTree};
-use crate::extensions::{ExtParam, ParseableExt};
+use crate::extensions::ParseableExt;
 use crate::miniscript::lex::{lex, Token as Tk, TokenIter};
 use crate::miniscript::limits::{
     MAX_OPS_PER_SCRIPT, MAX_SCRIPT_SIZE, MAX_STANDARD_P2WSH_SCRIPT_SIZE,
@@ -485,20 +485,18 @@ where
     }
 }
 
-impl<Pk, Ext, ExtQ, PArg, QArg> TranslateExt<Ext, ExtQ, PArg, QArg> for LegacyCSFSCov<Pk, Ext>
+impl<Pk, Ext, ExtQ> TranslateExt<Ext, ExtQ> for LegacyCSFSCov<Pk, Ext>
 where
     Pk: MiniscriptKey,
     Ext: Extension,
     ExtQ: Extension,
-    Ext: TranslateExt<Ext, ExtQ, PArg, QArg, Output = ExtQ>,
-    PArg: ExtParam,
-    QArg: ExtParam,
+    Ext: TranslateExt<Ext, ExtQ, Output = ExtQ>,
 {
     type Output = LegacyCSFSCov<Pk, ExtQ>;
 
     fn translate_ext<T, E>(&self, translator: &mut T) -> Result<Self::Output, E>
     where
-        T: ExtTranslator<PArg, QArg, E>,
+        T: ExtTranslator<Ext, ExtQ, E>,
     {
         Ok(LegacyCSFSCov {
             pk: self.pk.clone(),

src/descriptor/csfs_cov/mod.rs

@@ -182,7 +182,7 @@ mod tests {
     }
 
     fn _satisfy_and_interpret(
-        desc: Descriptor<bitcoin::PublicKey, CovExtArgs>,
+        desc: Descriptor<bitcoin::PublicKey, CovenantExt<CovExtArgs>>,
         cov_sk: secp256k1_zkp::SecretKey,
     ) -> Result<(), Error> {
         assert_eq!(desc.desc_type(), DescriptorType::Cov);