Struct rustlr::generic_absyn::LBox

pub struct LBox<T> {
    pub exp: Box<T>,
    pub line: usize,
    pub column: usize,
    pub src_id: usize,
}

custom smart pointer that encapsulates line number, column and other information for warnings and error messages after the parsing stage. Implements Deref and DerefMut so the encapsulated expression can be accessed as in a standard Box. For example, an abstract syntax type can be defined by

 enum Expr {
   Val(i64),
   PlusExpr(LBox<Expr>,LBox<Expr>),
   ...
 }

 fn check(e:&Expr) {
   match e {
     PlusExpr(a,b) => {
       println!("checking subexpressions on line {} and {}",a.line,b.line);
       check(a); check(b); // Deref coercion used here
     },
   ...

The RuntimeParser::lb function can be called from the semantic actions of a grammar to create LBoxed-values that include line/column information. LBox implements the Default trait if T does, so an LBox type can also serve as the absyntract syntax type for a grammar. The src_id field of LBox can be used to point to externally kept information about the source being compiled, such as the source file name when mulitple files are compiled together.

Fields

exp: Box<T>

line: usize

column: usize

src_id: usize

Implementations

impl<T> LBox<T>

pub fn new(e: T, ln: usize, col: usize) -> LBox<T>

pub fn set_src_id(&mut self, id: usize)

Trait Implementations

impl<T: Default> Default for LBox<T>

fn default() -> Self

Returns the “default value” for a type.

impl<T> Deref for LBox<T>

type Target = T

The resulting type after dereferencing.

fn deref(&self) -> &Self::Target

Dereferences the value.

impl<T> DerefMut for LBox<T>

fn deref_mut(&mut self) -> &mut Self::Target

Mutably dereferences the value.