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Cleaned up formatting and fixed bug in rev_binop
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@veddan
veddan committed Oct 24, 2012
1 parent 9d91529 commit 87b5f05
Showing 1 changed file with 119 additions and 105 deletions.
224 changes: 119 additions & 105 deletions src/rustc/middle/lint.rs
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Expand Up @@ -54,7 +54,7 @@ enum lint {
deprecated_pattern,
non_camel_case_types,
structural_records,
type_limits,
type_limits,

managed_heap_memory,
owned_heap_memory,
Expand Down Expand Up @@ -187,10 +187,10 @@ fn get_lint_dict() -> lint_dict {
desc: ~"allow legacy modes",
default: forbid}),

(~"type_limits",
@{lint: type_limits,
desc: ~"comparisons made useless by limits of the types involved",
default: warn})
(~"type_limits",
@{lint: type_limits,
desc: ~"comparisons made useless by limits of the types involved",
default: warn})

/* FIXME(#3266)--make liveness warnings lintable
(~"unused_variable",
Expand Down Expand Up @@ -403,7 +403,7 @@ fn check_item(i: @ast::item, cx: ty::ctxt) {
check_item_heap(cx, i);
check_item_structural_records(cx, i);
check_item_deprecated_modes(cx, i);
check_item_type_limits(cx, i);
check_item_type_limits(cx, i);
}

// Take a visitor, and modify it so that it will not proceed past subitems.
Expand Down Expand Up @@ -438,105 +438,119 @@ fn check_item_while_true(cx: ty::ctxt, it: @ast::item) {
}

fn check_item_type_limits(cx: ty::ctxt, it: @ast::item) {
pure fn is_valid<T: cmp::Ord>(binop: ast::binop, v: T, min: T, max: T) -> bool {
match binop {
ast::lt => v <= max,
ast::le => v < max,
ast::gt => v >= min,
ast::ge => v > min,
ast::eq | ast::ne => v >= min && v <= max,
_ => fail
}
}

pure fn rev_binop(binop: ast::binop) -> ast::binop {
match binop {
ast::lt => ast::ge,
ast::le => ast::gt,
ast::gt => ast::le,
ast::ge => ast::lt,
_ => binop
}
}

fn check_limits(cx: ty::ctxt, binop: ast::binop, l: &ast::expr,
r: &ast::expr) -> bool {
let (lit, expr, swap) = match (l.node, r.node) {
(ast::expr_lit(_), _) => (l, r, true),
(_, ast::expr_lit(_)) => (r, l, false),
_ => return true
};
// Normalize the binop so that the literal is always on the RHS in
// the comparison
let norm_binop = if (swap) {
rev_binop(binop)
} else {
binop
};
match ty::get(ty::expr_ty(cx, @*expr)).sty {
ty::ty_int(int_ty) => {
let (min, max): (i64, i64) = match int_ty {
ast::ty_i => (int::min_value as i64, int::max_value as i64),
ast::ty_char => (u32::min_value as i64, u32::max_value as i64),
ast::ty_i8 => (i8::min_value as i64, i8::max_value as i64),
ast::ty_i16 => (i16::min_value as i64, i16::max_value as i64),
ast::ty_i32 => (i32::min_value as i64, i32::max_value as i64),
ast::ty_i64 => (i64::min_value, i64::max_value)
};
let lit_val: i64 = match lit.node {
ast::expr_lit(@li) => match li.node {
ast::lit_int(v, _) => v,
ast::lit_uint(v, _) => v as i64,
ast::lit_int_unsuffixed(v) => v,
_ => return true
},
_ => fail
};
is_valid(norm_binop, lit_val, min, max)
}
ty::ty_uint(uint_ty) => {
let (min, max): (u64, u64) = match uint_ty {
ast::ty_u => (uint::min_value as u64, uint::max_value as u64),
ast::ty_u8 => (u8::min_value as u64, u8::max_value as u64),
ast::ty_u16 => (u16::min_value as u64, u16::max_value as u64),
ast::ty_u32 => (u32::min_value as u64, u32::max_value as u64),
ast::ty_u64 => (u64::min_value, u64::max_value)
};
let lit_val: u64 = match lit.node {
ast::expr_lit(@li) => match li.node {
ast::lit_int(v, _) => v as u64,
ast::lit_uint(v, _) => v,
ast::lit_int_unsuffixed(v) => v as u64,
_ => return true
},
_ => fail
};
is_valid(norm_binop, lit_val, min, max)
}
_ => true
}
}

let visit = item_stopping_visitor(visit::mk_simple_visitor(@{
visit_expr: fn@(e: @ast::expr) {
match e.node {
ast::expr_binary(binop, @l, @r) => {
match binop {
ast::eq | ast::lt | ast::le | ast::ne | ast::ge | ast::gt => {
if !check_limits(cx, binop, &l, &r) {
cx.sess.span_lint(type_limits, e.id, it.id, e.span,
~"comparison is useless due to type limits");
}
}
_ => ()
}
}
_ => ()
}
},
.. *visit::default_simple_visitor()
}));
visit::visit_item(it, (), visit);
pure fn is_valid<T: cmp::Ord>(binop: ast::binop, v: T,
min: T, max: T) -> bool {
match binop {
ast::lt => v <= max,
ast::le => v < max,
ast::gt => v >= min,
ast::ge => v > min,
ast::eq | ast::ne => v >= min && v <= max,
_ => fail
}
}

pure fn rev_binop(binop: ast::binop) -> ast::binop {
match binop {
ast::lt => ast::gt,
ast::le => ast::ge,
ast::gt => ast::lt,
ast::ge => ast::le,
_ => binop
}
}

pure fn int_ty_range(int_ty: ast::int_ty) -> (i64, i64) {
match int_ty {
ast::ty_i => (int::min_value as i64, int::max_value as i64),
ast::ty_char => (u32::min_value as i64, u32::max_value as i64),
ast::ty_i8 => (i8::min_value as i64, i8::max_value as i64),
ast::ty_i16 => (i16::min_value as i64, i16::max_value as i64),
ast::ty_i32 => (i32::min_value as i64, i32::max_value as i64),
ast::ty_i64 => (i64::min_value, i64::max_value)
}
}

pure fn uint_ty_range(uint_ty: ast::uint_ty) -> (u64, u64) {
match uint_ty {
ast::ty_u => (uint::min_value as u64, uint::max_value as u64),
ast::ty_u8 => (u8::min_value as u64, u8::max_value as u64),
ast::ty_u16 => (u16::min_value as u64, u16::max_value as u64),
ast::ty_u32 => (u32::min_value as u64, u32::max_value as u64),
ast::ty_u64 => (u64::min_value, u64::max_value)
}
}

fn check_limits(cx: ty::ctxt, binop: ast::binop, l: &ast::expr,
r: &ast::expr) -> bool {
let (lit, expr, swap) = match (l.node, r.node) {
(ast::expr_lit(_), _) => (l, r, true),
(_, ast::expr_lit(_)) => (r, l, false),
_ => return true
};
// Normalize the binop so that the literal is always on the RHS in
// the comparison
let norm_binop = if (swap) {
rev_binop(binop)
} else {
binop
};
match ty::get(ty::expr_ty(cx, @*expr)).sty {
ty::ty_int(int_ty) => {
let (min, max) = int_ty_range(int_ty);
let lit_val: i64 = match lit.node {
ast::expr_lit(@li) => match li.node {
ast::lit_int(v, _) => v,
ast::lit_uint(v, _) => v as i64,
ast::lit_int_unsuffixed(v) => v,
_ => return true
},
_ => fail
};
is_valid(norm_binop, lit_val, min, max)
}
ty::ty_uint(uint_ty) => {
let (min, max): (u64, u64) = uint_ty_range(uint_ty);
let lit_val: u64 = match lit.node {
ast::expr_lit(@li) => match li.node {
ast::lit_int(v, _) => v as u64,
ast::lit_uint(v, _) => v,
ast::lit_int_unsuffixed(v) => v as u64,
_ => return true
},
_ => fail
};
is_valid(norm_binop, lit_val, min, max)
}
_ => true
}
}

pure fn is_comparison(binop: ast::binop) -> bool {
match binop {
ast::eq | ast::lt | ast::le |
ast::ne | ast::ge | ast::gt => true,
_ => false
}
}

let visit = item_stopping_visitor(visit::mk_simple_visitor(@{
visit_expr: fn@(e: @ast::expr) {
match e.node {
ast::expr_binary(binop, @l, @r) => {
if is_comparison(binop)
&& !check_limits(cx, binop, &l, &r) {
cx.sess.span_lint(
type_limits, e.id, it.id, e.span,
~"comparison is useless due to type limits");
}
}
_ => ()
}
},
.. *visit::default_simple_visitor()
}));
visit::visit_item(it, (), visit);
}

fn check_item_structural_records(cx: ty::ctxt, it: @ast::item) {
Expand Down

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