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.
No dropped results
Calling a function and ignoring its value is almost always a bug — a missing let, a forgotten return. POLYTONE turns it into a compile error.
fn build() -> Int = 42
build()The compiler answers
error: this Int result is discarded — bind it with 'let' or return it (line 2, column 1)fn build() -> Int = 42
let result = build()
print("{result}")Fixed — and it runs
42