Error Lab
Every diagnostic below is the real output of ptc, not a mock-up. Pick a mistake, read how the compiler teaches the canonical form, then flip to the fix.
Module calls are qualified
Imported names are never injected into your namespace — a cross-module call always states its origin, and the error spells the exact form.
import mathx
print("{double(21)}")The compiler answers
error: 'double' lives in module 'mathx' — module functions are called qualified: mathx.double(...) (line 2, column 9)import mathx
print("{mathx.double(21)}")Fixed — and it runs
42