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Add operator precedence for pretty printer

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Previously it just added parentheses in excess.
e.g. ((1 + 2) + 3) + 4
This commit is contained in:
Garming Sam
2015-08-06 19:55:27 +12:00
parent c67a34b9e5
commit c0c6af7f07
1 changed files with 25 additions and 2 deletions
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23
src/libsyntax/print/pprust.rs
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@@ -1555,6 +1555,21 @@ impl<'a> State<'a> {
self.pclose()
}
pub fn check_expr_bin_needs_paren(&mut self, sub_expr: &ast::Expr,
binop: ast::BinOp) -> bool {
match sub_expr.node {
ast::ExprBinary(ref sub_op, _, _) => {
if ast_util::operator_prec(sub_op.node) <
ast_util::operator_prec(binop.node) {
true
} else {
false
}
}
_ => true
}
}
pub fn print_expr_maybe_paren(&mut self, expr: &ast::Expr) -> io::Result<()> {
let needs_par = needs_parentheses(expr);
if needs_par {
@@ -1670,10 +1685,18 @@ impl<'a> State<'a> {
op: ast::BinOp,
lhs: &ast::Expr,
rhs: &ast::Expr) -> io::Result<()> {
if self.check_expr_bin_needs_paren(lhs, op) {
try!(self.print_expr_maybe_paren(lhs));
} else {
try!(self.print_expr(lhs));
}
try!(space(&mut self.s));
try!(self.word_space(ast_util::binop_to_string(op.node)));
if self.check_expr_bin_needs_paren(rhs, op) {
self.print_expr_maybe_paren(rhs)
} else {
self.print_expr(rhs)
}
}
fn print_expr_unary(&mut self,