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Add additional parenthesis for binary ops in pretty printer #27613

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Merged
merged 4 commits into from
Aug 21, 2015
Merged

Add additional parenthesis for binary ops in pretty printer #27613

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c67a34b
Binary ops should add parenthesis to each side
GSam Aug 6, 2015
c0c6af7
Add operator precedence for pretty printer
GSam Aug 6, 2015
6a51de0
Casts are a type of binop
GSam Aug 6, 2015
22baa46
Avoid adding extra paren with two casts
GSam Aug 9, 2015
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33 changes: 30 additions & 3 deletions src/libsyntax/print/pprust.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -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 {
Expand Down Expand Up @@ -1670,10 +1685,18 @@ impl<'a> State<'a> {
op: ast::BinOp,
lhs: &ast::Expr,
rhs: &ast::Expr) -> io::Result<()> {
try!(self.print_expr(lhs));
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)));
self.print_expr(rhs)
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,
Expand Down Expand Up @@ -1730,7 +1753,11 @@ impl<'a> State<'a> {
try!(self.print_literal(&**lit));
}
ast::ExprCast(ref expr, ref ty) => {
try!(self.print_expr(&**expr));
if let ast::ExprCast(..) = expr.node {
try!(self.print_expr(&**expr));
} else {
try!(self.print_expr_maybe_paren(&**expr));
}
try!(space(&mut self.s));
try!(self.word_space("as"));
try!(self.print_type(&**ty));
Expand Down