Diagnostics

Diagnostics name the file, line and column (in imported modules, their own), with the offending source line.

Code	Meaning
E0001	a type or structure error: a mismatch, an unknown name, shadowing, a missing return, ? outside an Option/Result function, an if expression without else, == on a composite value without Eq, a duplicate function or behavior instance, an instance whose functions do not match its behavior, a malformed program
E0211	a call exceeds the caller’s sandbox ceiling
E0212	a region violation: a handle entering a sandbox it exceeds, or a write under a read-only grant
E0213	a malformed capability list (unknown family or mode)
E0214	a spawn lists more capabilities than its parent holds
E0215	a call inside a spawn needs a capability the region lacks
E0216	an attenuated import of a module already imported without attenuation
E0218	a provider call in a restricted region uses a family outside it
E0219	a function uses a capability it is not granted (no ambient authority)
E0220	a compiler-internal primitive used outside the compiler’s own sources
E0221	an imported module cannot be found
E0222	a name in the wrong case: types, behaviors and variants start uppercase, values and functions lowercase; single uppercase letters are reserved for type parameters
E0223	an unqualified use of a name that two imported modules both export
E0224	a library declares an instance of a behavior and a type it owns neither of
E0225	two instances of one behavior overlap at the same level (no specialization)
E0226	a generic function uses a behavior it does not list in @needs, or a call’s needs have no instance
E0227	a type parameter cannot be inferred from the arguments, the expected type or one fitting instance
E0228	a generic function calls itself at ever larger types (instantiation does not terminate)
E0301	a known value violates its constraint type
E0401	a builder is not consumed on some path
E0402	a builder is used twice
E0403	a builder is used inside a loop or lambda it was not created in
E0404	a builder type nested inside another type
E0410	a vector’s lane type or lane count is not allowed
E0411	a vector type nested inside another type, or a vector captured by a lambda or spawn
E0412	a vector literal, splat or lanes without a vector slot to take its type from
E0901	known(x) on a residual value

Runtime failures (overflow, division by zero, index out of range, a failed conversion, a broken constraint, an assertion, todo) abort with a message naming what failed. Inside a spawn region they become Err(RegionError).

Notes (note: ...) are not errors: they report reduction budgets that ran out, residual notes recorded, and whether the build was signed.