Struct ParserState

pub struct ParserState {
    pub allow_then: bool,
    pub allow_of: bool,
    pub allow_loop_control: bool,
    pub allow_return: bool,
    pub expr_end_at_eol: bool,
}

State that can be used to determine if certain parse trees are valid (e.g. if a checking if a break expression is inside a loop).

The state cannot be mutated directly; it can only be changed when parsing using the Parser::try_parse_with_state method.

Fields

allow_then: bool

Whether a then expression is allowed in the current context.

then expressions are only allowed after the conditions of if, while and loop expressions.

allow_of: bool

Whether an of expression is allowed in the current context.

of expressions are only allowed after the range of sum and product expressions.

allow_loop_control: bool

Whether loop control expressions are allowed in the current context.

Loop control expressions are break and continue expressions. They are only allowed inside loop expressions, such as while, loop, and for.

allow_return: bool

Whether a return expression is allowed in the current context.

return expressions are only allowed inside function assignments.

expr_end_at_eol: bool

Whether to require the current expression to end at the end of the line.

This is enabled on when parsing the expression of a return or break expression. The expression returned by the return / break expression must lie on the same line as the return / break keyword to prevent confusion in cases like:

if k > n return

sub = n - k

Without this requirement, the return expression would eagerly consume the assignment sub = n - k, resulting in the above code being treated as:

if k > n {
   return sub = n - k
}

Which is almost certainly not what the user intended.

Trait Implementations

impl Clone for ParserState

fn clone(&self) -> ParserState

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ParserState

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for ParserState

fn default() -> ParserState

Returns the “default value” for a type.