sqlparser_derive embeds its build-time manifest directory in the proc-macro binary #2724

sqlparser_derive 0.6.0 embeds its build-time CARGO_MANIFEST_DIR in the proc-macro binary through DERIVE_CRATE_DIR in read_dialect_mod_file. Changing only that environment value changes the final binary, even without incremental compilation or debug info. Under Bazel this is a temporary sandbox path, so identical recorded action inputs produce different outputs and the cached macro retains the producer's source location.

This is also a source-tree dependency during macro expansion, independent of Bazel: derive_dialect! reads sqlparser/src/dialect/mod.rs to discover the Dialect method signatures. Compiled dependencies alone are insufficient; expansion fails if none of the searched source trees is present.

The repro compiles the same published source twice with the same dependencies and rustc arguments, changing only /tmp/sqlparser-a to /tmp/sqlparser-b:

$ git clone https://gist.github.com/595a35ecfc805046695680b837d79cc5.git sqlparser-manifest-repro && cd sqlparser-manifest-repro
$ sh repro.sh
rustc 1.98.0 (88d9e12ae 2026-08-18)
binary: rustc
commit-hash: 88d9e12ae178fab0fb5cc050a94da85685d449ea
commit-date: 2026-08-18
host: aarch64-unknown-linux-gnu
release: 1.98.0
LLVM version: 22.1.8
   Compiling proc-macro2 v1.0.93
   Compiling unicode-ident v1.0.27
   Compiling quote v1.0.37
   Compiling syn v3.0.3
   Compiling sqlparser-repro-deps v0.0.0 (/var/tmp/sqlparser-manifest-repro/deps)
    Finished `release` profile [optimized] target(s) in 3.58s
f8ab25524043be6591fc56954d3e860b4b431283a058c404c05e62a8d3494afc  sqlparser-a.so
6281c9bf299132340f68453662a1c966191076951c1484b70323386ecc0a8378  sqlparser-b.so
/tmp/sqlparser-a
/tmp/sqlparser-b

The proposed fix in #2725 stores those signatures as macro tokens in the compiled sqlparser library, which passes them to the proc macro during expansion. The proc-macro binary and compiled sqlparser dependency are sufficient; neither crate's source tree needs to remain available. Verified by building both crates, deleting their source trees, then compiling and running a consumer: this fails on unpatched upstream and passes with the fix.

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