Error catalog

Format: file:line:column: message. Each one below with cause and fix.

Parsing

Error	Cause → fix
expected ':'	Missing colon in a header/condition → add :
expected an indented block	Nothing after : → add an indented line
expected at least one statement in the block	Empty block → at least one statement
inconsistent indentation	Mixed indents → 4 spaces everywhere
unexpected ... in an expression	Garbage in an expression; common cause — #var with no space read as a variable, or vice versa a comment ate code
unexpected end of line in an expression	Truncated expression (dangling +, unclosed ()
unterminated text literal	Missing closing "
expected a variable name after '$'	$ + space/end → $name must be joined
cannot assign to this expression	Not a target on the left (index chains and properties are assignable; anything else is not)
unknown type '...'	In a function/argument annotation — only number text string boolean bool list map player
unknown command attribute '...'	After the command name — only permission/description
expected 'in' after the loop variable	for x in ...: — in is missing
'break' outside of a loop	break/continue only inside loops

Compilation

Error	Cause → fix
unknown function 'x'	No builtin and no own function (check arity: substring/2 vs /3)
unknown variable 'x'	Local not declared; or a shadowed builtin (let player = ...); or a lone typo
unknown statement or function 'x'	A lone unknown name on a line
... needs an event or command context and cannot be used in a function	Effects, sender()/arg(), $/#, player(), properties, index reads live only in triggers/commands; functions do pure math
duplicate trigger for event / declared twice	Two identical on/command/function in one file
function 'f' expects N argument(s), got M	Your own function's arity
argument N of 'x' must be ...	Type doesn't convert (e.g. a list into teleport)
unsupported event '...'	No such event in the table

Runtime (EvalException; the handler logs it and carries on)

Error	Cause
division by zero (+ in modulo)	Zero divisor — instead of NaN, deliberately
cannot use X as a number	Arithmetic with null/garbage — initialize
index N is out of bounds	Index past a list (out-of-range read is null, write is this error)
cannot assign into X	x[i] = v where x is not a list/map
unknown function 'x' with N argument(s)	Dynamic call missed KNOWN (shouldn't happen after compilation)
unknown player property 'x'	Typo in a property
no player in context...	#var write with no player (server start, bench)
player 'x' is not online	requirePlayer with an offline name string
unknown material/potion effect/world	Garbage in material()/add-effect()/world()
script command '/x' is not declared in plugin.yml	Plugin warning, not a script error

Infrastructure (not yours)

ASM NegativeArraySizeException / VerifyError: Bad type on operand stack during assembly are packer bugs (dup/receiver/descriptors) — all known ones are fixed; if you see one again, look at emitDispatch/emitCall/Builtins.