Types and aliases
AG1001 — Type parameter '{param}' (no default) must come before parameters that have defaults in '{alias}'.
Default severity: error.
A type alias lists its type parameters left to right, and — like default function arguments — every parameter with a default must come after the parameters that have none. Otherwise a caller who omits a middle argument leaves a later, required one with no way to be positioned.
How to fix: reorder the type parameters so all defaulted ones are last.
AG1002 — Type '{alias}' is not a value-parameterized type but was given {count} value {argumentWord} (referenced in '{context}').
Default severity: error.
Some type aliases take value arguments in parentheses (like a validated length), and some take none. This fires when you passed value arguments to an alias that accepts none.
How to fix: drop the parenthesized arguments, or point at the alias you actually meant to parameterize.
AG1003 — {alias} expects at most {max} value {argumentWord}, got {count} (referenced in '{context}').
Default severity: error.
A value-parameterized alias accepts a fixed maximum number of value arguments, and you supplied more than it declares.
How to fix: remove the extra arguments, or check whether you meant a different alias with more parameters.
AG1004 — '{alias}' is a value-parameterized type and requires value arguments — write '{alias}({formals})' (referenced in '{context}').
Default severity: error.
This alias is value-parameterized: it needs its value arguments supplied in parentheses before it can be used as a type. Writing the bare name leaves those parameters unfilled.
How to fix: call it with its arguments, following the form the message shows for that alias.
AG1005 — {alias} requires at least {min} value {argumentWord} (referenced in '{context}').
Default severity: error.
A value-parameterized alias requires at least some minimum number of value arguments, and you supplied fewer.
How to fix: add the missing arguments; the message names how many the alias needs.
AG1006 — Type alias '{alias}' is not defined (referenced in '{context}').
Default severity: error.
A type name was used that has no type declaration in scope and is not a built-in type. The checker resolves every type name against the aliases visible in the file plus its imports.
How to fix: declare the alias, import it from the module that defines it, or fix a typo in the name.
AG1007 — Generic type '{alias}' requires type arguments (referenced in '{context}').
Default severity: error.
This is a generic type — it is parameterized by other types (like the element type of a list) — and it cannot be used bare. The type arguments are required.
How to fix: supply the type arguments in angle brackets, e.g. write the element type the generic wraps.
AG1008 — {alias} expects {expected} type {argumentWord}, got {count} (referenced in '{context}').
Default severity: error.
A built-in generic type (such as an array or Record) was given the wrong number of type arguments. Each built-in generic takes an exact count.
How to fix: supply exactly the number of type arguments the message names.
AG1009 — Unknown generic type '{alias}' (referenced in '{context}').
Default severity: error.
A generic type name was used with type arguments, but no generic type by that name is defined or imported.
How to fix: define or import the generic, or fix the name.
AG1010 — Type '{alias}' is not a generic type (referenced in '{context}').
Default severity: error.
Type arguments in angle brackets were applied to a name that is not a generic type, so it has no parameters to fill.
How to fix: remove the type arguments, or reference the generic type you meant.
AG1011 — {alias} expects at most {max} type {argumentWord}, got {count} (referenced in '{context}').
Default severity: error.
A generic type accepts a fixed maximum number of type arguments, and you supplied more than it declares.
How to fix: remove the extra type arguments.
AG1012 — {alias} requires at least {min} type {argumentWord} (referenced in '{context}').
Default severity: error.
A generic type requires at least some minimum number of type arguments, and you supplied fewer.
How to fix: add the missing type arguments; the message names how many are needed.
AG1013 — {name} is not a type; {hint}
Default severity: error.
A type pattern (x is T, or a match arm p: T) named something that is not a type. After is, a bare identifier is always read as a type reference — the old always-true binder form was retired — so a variable name or a JavaScript class name (like Date) in that position is an error rather than a silent match-anything.
How to fix: if you meant a type, declare or import it. If you meant to bind the value, write const name = x instead. For JavaScript classes, use is object or a helper function — type patterns only test Agency types.