'mismatched types solana_sdk::pubkey::Pubkey, found Pubkey' means two solana-program versions — drop git deps, pin versions

Symptom: a Rust Solana client fails to compile with errors inside other crates' source, e.g. in account-decoder/src/parse_account_data.rs:

error[E0308]: mismatched types
   expected `solana_sdk::pubkey::Pubkey`, found `Pubkey`
   = note: `Pubkey` and `solana_sdk::pubkey::Pubkey` have similar names,
           but are actually distinct types

with the note pointing at solana-program-1.18.1/src/pubkey.rs.

Cause: two *different versions* of solana-program are in the dependency graph. Cargo allows semver-incompatible duplicates to coexist, so Pubkey from one copy is a genuinely different type from Pubkey in the other, and no amount of use statements will reconcile them. Nothing is wrong with your code.

The usual trigger is a dependency pulled from git rather than crates.io, which resolves to whatever master currently is:

solana-quic-client = { git = "https://github.com/solana-labs/solana.git", branch = "master" }

Fix: replace git dependencies with a published version matching the rest of your Solana crates:

solana-quic-client = "1.18.1"

Diagnosis command: cargo tree -d -i solana-program (or cargo tree -d) lists duplicated crates and, crucially, who pulls each one — that tells you which dependency to pin or bump. Every solana-* crate in the tree must be at the same version; a single stray one (often spl-token, spl-associated-token-account, anchor-spl, or an anchor-lang whose pinned solana-program differs) reproduces this. Also delete Cargo.lock and re-resolve after pinning, otherwise the old duplicate can persist. Same class of error appears after the solana-sdk crate split, where the fix is likewise aligning versions rather than changing imports.

Source: adapted from a Stack Exchange answer by MHCH (question by MHCH), https://solana.stackexchange.com/questions/9927/mismatched-types-solana-sdkpubkeypubkey-found-pubkey — CC BY-SA 4.0