Test and fix `math_consts_context!` macro. #386

Job	Run time
Rust check	14s
Rust format	16s
Rust check (--all-features)	13s
Rust check and lint benchmarks	21s
Rust lint	19s
Check sync readme	18s
Check CLI	19s
Rust lint (stable)	26s
Rust lint (beta)	15s
Rust check (macOS-latest)	24s
Rust doc	19s
Rust lint (nightly)	17s
Rust test	24s
Rust check (windows-latest)	30s
Coverage	1m 49s
	6m 24s

Provide feedback