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Refactored CastPass.
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@Robzz
Robzz committed Aug 23, 2015
1 parent e80f247 commit 3af2e3b
Showing 1 changed file with 70 additions and 73 deletions.
143 changes: 70 additions & 73 deletions src/types.rs
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Expand Up @@ -134,6 +134,72 @@ fn is_isize_or_usize(typ: &ty::TyS) -> bool {
}
}

fn span_precision_loss_lint(cx: &Context, expr: &Expr, cast_from: &ty::TyS, cast_to_f64: bool) {
let mantissa_nbits = if cast_to_f64 {52} else {23};
let arch_dependent = is_isize_or_usize(cast_from) && cast_to_f64;
let arch_dependent_str = "on targets with 64-bit wide pointers ";
let from_nbits_str = if arch_dependent {"64".to_owned()}
else if is_isize_or_usize(cast_from) {"32 or 64".to_owned()}
else {int_ty_to_nbits(cast_from).to_string()};
span_lint(cx, CAST_PRECISION_LOSS, expr.span,
&format!("casting {0} to {1} causes a loss of precision {2}\
({0} is {3} bits wide, but {1}'s mantissa is only {4} bits wide)",
cast_from, if cast_to_f64 {"f64"} else {"f32"},
if arch_dependent {arch_dependent_str} else {""},
from_nbits_str,
mantissa_nbits));
}

enum ArchSuffix {
_32, _64, None
}

fn check_truncation_and_wrapping(cx: &Context, expr: &Expr, cast_from: &ty::TyS, cast_to: &ty::TyS) {
let arch_64_suffix = " on targets with 64-bit wide pointers";
let arch_32_suffix = " on targets with 32-bit wide pointers";
let cast_unsigned_to_signed = !cast_from.is_signed() && cast_to.is_signed();
let (from_nbits, to_nbits) = (int_ty_to_nbits(cast_from), int_ty_to_nbits(cast_to));
let (span_truncation, suffix_truncation, span_wrap, suffix_wrap) =
match (is_isize_or_usize(cast_from), is_isize_or_usize(cast_to)) {
(true, true) | (false, false) => (
to_nbits < from_nbits,
ArchSuffix::None,
to_nbits == from_nbits && cast_unsigned_to_signed,
ArchSuffix::None
),
(true, false) => (
to_nbits <= 32,
if to_nbits == 32 {ArchSuffix::_64} else {ArchSuffix::None},
to_nbits <= 32 && cast_unsigned_to_signed,
ArchSuffix::_32
),
(false, true) => (
from_nbits == 64,
ArchSuffix::_32,
cast_unsigned_to_signed,
if from_nbits == 64 {ArchSuffix::_64} else {ArchSuffix::_32}
),
};
if span_truncation {
span_lint(cx, CAST_POSSIBLE_TRUNCATION, expr.span,
&format!("casting {} to {} may truncate the value{}",
cast_from, cast_to,
match suffix_truncation {
ArchSuffix::_32 => arch_32_suffix,
ArchSuffix::_64 => arch_64_suffix,
ArchSuffix::None => "" }));
}
if span_wrap {
span_lint(cx, CAST_POSSIBLE_WRAP, expr.span,
&format!("casting {} to {} may wrap around the value{}",
cast_from, cast_to,
match suffix_wrap {
ArchSuffix::_32 => arch_32_suffix,
ArchSuffix::_64 => arch_64_suffix,
ArchSuffix::None => "" }));
}
}

impl LintPass for CastPass {
fn get_lints(&self) -> LintArray {
lint_array!(CAST_PRECISION_LOSS,
Expand All @@ -149,33 +215,9 @@ impl LintPass for CastPass {
match (cast_from.is_integral(), cast_to.is_integral()) {
(true, false) => {
let from_nbits = int_ty_to_nbits(cast_from);
let to_nbits : usize = match cast_to.sty {
ty::TyFloat(ast::TyF32) => 32,
ty::TyFloat(ast::TyF64) => 64,
_ => 0
};
if from_nbits != 0 {
// When casting to f32, precision loss would occur regardless of the arch
if is_isize_or_usize(cast_from) {
if to_nbits == 64 {
span_lint(cx, CAST_PRECISION_LOSS, expr.span,
&format!("casting {0} to f64 causes a loss of precision on targets with 64-bit wide pointers \
({0} is 64 bits wide, but f64's mantissa is only 52 bits wide)",
cast_from));
}
else {
span_lint(cx, CAST_PRECISION_LOSS, expr.span,
&format!("casting {0} to f32 causes a loss of precision \
({0} is 32 or 64 bits wide, but f32's mantissa is only 23 bits wide)",
cast_from));
}
}
else if from_nbits >= to_nbits {
span_lint(cx, CAST_PRECISION_LOSS, expr.span,
&format!("casting {0} to {1} causes a loss of precision \
({0} is {2} bits wide, but {1}'s mantissa is only {3} bits wide)",
cast_from, cast_to, from_nbits, if to_nbits == 64 {52} else {23} ));
}
let to_nbits = if let ty::TyFloat(ast::TyF32) = cast_to.sty {32} else {64};
if is_isize_or_usize(cast_from) || from_nbits >= to_nbits {
span_precision_loss_lint(cx, expr, cast_from, to_nbits == 64);
}
},
(false, true) => {
Expand All @@ -187,56 +229,11 @@ impl LintPass for CastPass {
}
},
(true, true) => {
let from_nbits = int_ty_to_nbits(cast_from);
let to_nbits = int_ty_to_nbits(cast_to);
if cast_from.is_signed() && !cast_to.is_signed() {
span_lint(cx, CAST_SIGN_LOSS, expr.span,
&format!("casting {} to {} may lose the sign of the value", cast_from, cast_to));
}
match (is_isize_or_usize(cast_from), is_isize_or_usize(cast_to)) {
(true, true) | (false, false) =>
if to_nbits < from_nbits {
span_lint(cx, CAST_POSSIBLE_TRUNCATION, expr.span,
&format!("casting {} to {} may truncate the value", cast_from, cast_to));
}
else if !cast_from.is_signed() && cast_to.is_signed() && to_nbits == from_nbits {
span_lint(cx, CAST_POSSIBLE_WRAP, expr.span,
&format!("casting {} to {} may wrap around the value", cast_from, cast_to));
},
(true, false) =>
if to_nbits == 32 {
span_lint(cx, CAST_POSSIBLE_TRUNCATION, expr.span,
&format!("casting {} to {} may truncate the value on targets with 64-bit wide pointers",
cast_from, cast_to));
if !cast_from.is_signed() && cast_to.is_signed() {
span_lint(cx, CAST_POSSIBLE_WRAP, expr.span,
&format!("casting {} to {} may wrap around the value on targets with 32-bit wide pointers",
cast_from, cast_to));
}
}
else if to_nbits < 32 {
span_lint(cx, CAST_POSSIBLE_TRUNCATION, expr.span,
&format!("casting {} to {} may truncate the value", cast_from, cast_to));
},
(false, true) =>
if from_nbits == 64 {
span_lint(cx, CAST_POSSIBLE_TRUNCATION, expr.span,
&format!("casting {} to {} may truncate the value on targets with 32-bit wide pointers",
cast_from, cast_to));
if !cast_from.is_signed() && cast_to.is_signed() {
span_lint(cx, CAST_POSSIBLE_WRAP, expr.span,
&format!("casting {} to {} may wrap around the value on targets with 64-bit wide pointers",
cast_from, cast_to));
}
}
else {
if !cast_from.is_signed() && cast_to.is_signed() {
span_lint(cx, CAST_POSSIBLE_WRAP, expr.span,
&format!("casting {} to {} may wrap around the value on targets with 32-bit wide pointers",
cast_from, cast_to));
}
}
}
check_truncation_and_wrapping(cx, expr, cast_from, cast_to);
}
(false, false) => {
if let (&ty::TyFloat(ast::TyF64),
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