Merge #14934: Descriptor expansion cache clarifications

2e68ffaf205866e4cea71f64e79bbfb89e17280a [doc] descriptor: explain GetPubKey() usage with cached public key (Sjors Provoost)
2290269759ad10cc2e35958c7b0a63f3a7608621 scripted-diff: rename DescriptorImpl m_script_arg to m_subdescriptor_arg (Sjors Provoost)

Pull request description:

  I found the name `m_script_arg` to be confusing while reviewing https://github.com/bitcoin/bitcoin/pull/14646#discussion_r240677238. @sipa let me know if `m_subdescriptor_arg` is completely wrong.

  I also added an explanation of why we call `GetPubKey` when we don't ask it for a public key.

ACKs for top commit:
  laanwj:
    ACK 2e68ffaf205866e4cea71f64e79bbfb89e17280a

Tree-SHA512: 06698e9a91cdda93c043a82732793f0ad3cd91daa2513565953e9fa048d5573322fb534e9d0ea9ab736e6366be5921e2b8699c4f4b3693edab48039aaae06f78

1 files changed, 3 insertions, 3 deletions

diff --git a/src/script/descriptor.h b/src/script/descriptor.h
index 29915c6c92..a34e9f0d8a 100644
--- a/src/script/descriptor.h
+++ b/src/script/descriptor.h
@@ -47,9 +47,9 @@ struct Descriptor {
      *
      * pos: the position at which to expand the descriptor. If IsRange() is false, this is ignored.
      * provider: the provider to query for private keys in case of hardened derivation.
-     * output_script: the expanded scriptPubKeys will be put here.
+     * output_scripts: the expanded scriptPubKeys will be put here.
      * out: scripts and public keys necessary for solving the expanded scriptPubKeys will be put here (may be equal to provider).
-     * cache: vector which will be overwritten with cache data necessary to-evaluate the descriptor at this point without access to private keys.
+     * cache: vector which will be overwritten with cache data necessary to evaluate the descriptor at this point without access to private keys.
      */
     virtual bool Expand(int pos, const SigningProvider& provider, std::vector<CScript>& output_scripts, FlatSigningProvider& out, std::vector<unsigned char>* cache = nullptr) const = 0;
 
@@ -57,7 +57,7 @@ struct Descriptor {
      *
      * pos: the position at which to expand the descriptor. If IsRange() is false, this is ignored.
      * cache: vector from which cached expansion data will be read.
-     * output_script: the expanded scriptPubKeys will be put here.
+     * output_scripts: the expanded scriptPubKeys will be put here.
      * out: scripts and public keys necessary for solving the expanded scriptPubKeys will be put here (may be equal to provider).
      */
     virtual bool ExpandFromCache(int pos, const std::vector<unsigned char>& cache, std::vector<CScript>& output_scripts, FlatSigningProvider& out) const = 0;