Error struct for location expression validation failures.
This error is raised when attempting to resolve a location path for assignment
operations, but the expression does not represent a valid assignable location.
It also covers the write-time failures of Predicator.ContextLocation.put/3.
Error Types
Resolution failures:
:not_assignable- Expression cannot be used as an assignment target:invalid_node- Unknown or unsupported AST node type:undefined_variable- Variable referenced in bracket key is not defined:invalid_key- Bracket key is not a valid string or integer:computed_key- Computed expressions cannot be used as assignment keys
Write failures:
:not_a_container- Path traverses a value that is neither a map nor a list:invalid_index- List index in the path is out of range (negative)
Examples
# Cannot assign to literal values
%LocationError{
type: :not_assignable,
message: "Cannot assign to literal value",
details: %{expression_type: "literal value", value: 42}
}
# Cannot assign to function calls
%LocationError{
type: :not_assignable,
message: "Cannot assign to function call",
details: %{expression_type: "function call", value: "len"}
}
# Invalid bracket key type
%LocationError{
type: :invalid_key,
message: "Bracket key must be string or integer",
details: %{key_type: "boolean", key_value: true}
}Summary
Functions
Creates a LocationError for computed expressions used as bracket keys.
Creates a LocationError for an out-of-range list index in a location path.
Creates a LocationError for invalid bracket key types.
Creates a LocationError for invalid or unknown AST node types.
Creates a LocationError for assignment through a non-container value.
Creates a LocationError for non-assignable expressions.
Creates a LocationError for undefined variables in bracket keys.
Types
@type error_type() ::
:not_assignable
| :invalid_node
| :undefined_variable
| :invalid_key
| :computed_key
| :not_a_container
| :invalid_index
@type t() :: %Predicator.Errors.LocationError{ details: map(), message: binary(), type: error_type() }
Functions
Creates a LocationError for computed expressions used as bracket keys.
@spec invalid_index(binary(), integer(), non_neg_integer() | nil) :: t()
Creates a LocationError for an out-of-range list index in a location path.
path_index is the failing segment's 0-based index in the root-first location
path, or nil when the caller cannot identify one - see not_a_container/4.
It is unrelated to index: index is the out-of-range list index the
segment held, path_index is where that segment sits in the path itself, and
the two are different integers that happen to share a neighborhood in
details.
Creates a LocationError for invalid bracket key types.
Creates a LocationError for invalid or unknown AST node types.
@spec not_a_container(binary(), term(), term(), non_neg_integer() | nil) :: t()
Creates a LocationError for assignment through a non-container value.
Used when a location path traverses a value that is neither a map nor a list, so intermediate structure cannot be created without destroying existing data.
path_index is the failing segment's 0-based index in the root-first location
path, or nil when the caller cannot identify one. Predicator.Evaluator's
store path joins it with the run's segment-position table to point a store
failure at the segment that failed rather than at the location's root (px-ids).
It is deliberately a details key rather than a struct field: this struct is
shared with Predicator.ContextLocation.resolve/2 and
Predicator.Context.assign/3, which have no path to index.
Creates a LocationError for non-assignable expressions.
Used when an expression cannot be used as an assignment target (l-value).
Creates a LocationError for undefined variables in bracket keys.