Rollup merge of rust-lang#48432 - flip1995:lit_diag, r=oli-obk

Suggest type for overflowing bin/hex-literals

Fixes rust-lang#48073

For hexadecimal and binary literals, which overflow, it gives an additional note to the warning message, like in this [comment](rust-lang#48073 (comment)).

Additionally it will suggest a type (`X < Y`):
- `iX`: if literal fits in `uX` => `uX`, else => `iY`
- `-iX` => `iY`
- `uX` => `uY`

Exceptions: `isize`, `usize`. I don't think you can make a good suggestion here. The programmer has to figure it out on it's own in this case.

r? @oli-obk

src/librustc_lint/types.rs

@@ -150,11 +150,23 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeLimits {
 
  // Detect literal value out of range [min, max] inclusive
  // avoiding use of -min to prevent overflow/panic
- if (negative && v > max + 1) ||
- (!negative && v > max) {
- cx.span_lint(OVERFLOWING_LITERALS,
- e.span,
- &format!("literal out of range for {:?}", t));
+ if (negative && v > max + 1) || (!negative && v > max) {
+ if let Some(repr_str) = get_bin_hex_repr(cx, lit) {
+ report_bin_hex_error(
+ cx,
+ e,
+ ty::TyInt(t),
+ repr_str,
+ v,
+ negative,
+ );
+ return;
+ }
+ cx.span_lint(
+ OVERFLOWING_LITERALS,
+ e.span,
+ &format!("literal out of range for {:?}", t),
+ );
  return;
  }
  }
@@ -191,9 +203,22 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeLimits {
  }
  }
  }
- cx.span_lint(OVERFLOWING_LITERALS,
- e.span,
- &format!("literal out of range for {:?}", t));
+ if let Some(repr_str) = get_bin_hex_repr(cx, lit) {
+ report_bin_hex_error(
+ cx,
+ e,
+ ty::TyUint(t),
+ repr_str,
+ lit_val,
+ false,
+ );
+ return;
+ }
+ cx.span_lint(
+ OVERFLOWING_LITERALS,
+ e.span,
+ &format!("literal out of range for {:?}", t),
+ );
  }
  }
  ty::TyFloat(t) => {
@@ -338,6 +363,120 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeLimits {
  _ => false,
  }
  }
+
+ fn get_bin_hex_repr(cx: &LateContext, lit: &ast::Lit) -> Option<String> {
+ let src = cx.sess().codemap().span_to_snippet(lit.span).ok()?;
+ let firstch = src.chars().next()?;
+
+ if firstch == '0' {
+ match src.chars().nth(1) {
+ Some('x') | Some('b') => return Some(src),
+ _ => return None,
+ }
+ }
+
+ None
+ }
+
+ // This function finds the next fitting type and generates a suggestion string.
+ // It searches for fitting types in the following way (`X < Y`):
+ // - `iX`: if literal fits in `uX` => `uX`, else => `iY`
+ // - `-iX` => `iY`
+ // - `uX` => `uY`
+ //
+ // No suggestion for: `isize`, `usize`.
+ fn get_type_suggestion<'a>(
+ t: &ty::TypeVariants,
+ val: u128,
+ negative: bool,
+ ) -> Option<String> {
+ use syntax::ast::IntTy::*;
+ use syntax::ast::UintTy::*;
+ macro_rules! find_fit {
+ ($ty:expr, $val:expr, $negative:expr,
+ $($type:ident => [$($utypes:expr),*] => [$($itypes:expr),*]),+) => {
+ {
+ let _neg = if negative { 1 } else { 0 };
+ match $ty {
+ $($type => {
+ $(if !negative && val <= uint_ty_range($utypes).1 {
+ return Some(format!("{:?}", $utypes))
+ })*
+ $(if val <= int_ty_range($itypes).1 as u128 + _neg {
+ return Some(format!("{:?}", $itypes))
+ })*
+ None
+ },)*
+ _ => None
+ }
+ }
+ }
+ }
+ match t {
+ &ty::TyInt(i) => find_fit!(i, val, negative,
+ I8 => [U8] => [I16, I32, I64, I128],
+ I16 => [U16] => [I32, I64, I128],
+ I32 => [U32] => [I64, I128],
+ I64 => [U64] => [I128],
+ I128 => [U128] => []),
+ &ty::TyUint(u) => find_fit!(u, val, negative,
+ U8 => [U8, U16, U32, U64, U128] => [],
+ U16 => [U16, U32, U64, U128] => [],
+ U32 => [U32, U64, U128] => [],
+ U64 => [U64, U128] => [],
+ U128 => [U128] => []),
+ _ => None,
+ }
+ }
+
+ fn report_bin_hex_error(
+ cx: &LateContext,
+ expr: &hir::Expr,
+ ty: ty::TypeVariants,
+ repr_str: String,
+ val: u128,
+ negative: bool,
+ ) {
+ let (t, actually) = match ty {
+ ty::TyInt(t) => {
+ let bits = int_ty_bits(t, cx.sess().target.isize_ty);
+ let actually = (val << (128 - bits)) as i128 >> (128 - bits);
+ (format!("{:?}", t), actually.to_string())
+ }
+ ty::TyUint(t) => {
+ let bits = uint_ty_bits(t, cx.sess().target.usize_ty);
+ let actually = (val << (128 - bits)) >> (128 - bits);
+ (format!("{:?}", t), actually.to_string())
+ }
+ _ => bug!(),
+ };
+ let mut err = cx.struct_span_lint(
+ OVERFLOWING_LITERALS,
+ expr.span,
+ &format!("literal out of range for {}", t),
+ );
+ err.note(&format!(
+ "the literal `{}` (decimal `{}`) does not fit into \
+ an `{}` and will become `{}{}`",
+ repr_str, val, t, actually, t
+ ));
+ if let Some(sugg_ty) =
+ get_type_suggestion(&cx.tables.node_id_to_type(expr.hir_id).sty, val, negative)
+ {
+ if let Some(pos) = repr_str.chars().position(|c| c == 'i' || c == 'u') {
+ let (sans_suffix, _) = repr_str.split_at(pos);
+ err.span_suggestion(
+ expr.span,
+ &format!("consider using `{}` instead", sugg_ty),
+ format!("{}{}", sans_suffix, sugg_ty),
+ );
+ } else {
+ err.help(&format!("consider using `{}` instead", sugg_ty));
+ }
+ }
+
+ err.emit();
+ }
  }
 }
 

src/test/ui/lint/type-overflow.rs

@@ -0,0 +1,33 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// must-compile-successfully
+
+#![feature(i128_type)]
+
+fn main() {
+ let error = 255i8; //~WARNING literal out of range for i8
+
+ let ok = 0b1000_0001; // should be ok -> i32
+ let ok = 0b0111_1111i8; // should be ok -> 127i8
+
+ let fail = 0b1000_0001i8; //~WARNING literal out of range for i8
+
+ let fail = 0x8000_0000_0000_0000i64; //~WARNING literal out of range for i64
+
+ let fail = 0x1_FFFF_FFFFu32; //~WARNING literal out of range for u32
+
+ let fail: i128 = 0x8000_0000_0000_0000_0000_0000_0000_0000;
+ //~^ WARNING literal out of range for i128
+
+ let fail = 0x8FFF_FFFF_FFFF_FFFE; //~WARNING literal out of range for i32
+
+ let fail = -0b1111_1111i8; //~WARNING literal out of range for i8
+}

src/test/ui/lint/type-overflow.stderr

@@ -0,0 +1,58 @@
+warning: literal out of range for i8
+ --> $DIR/type-overflow.rs:16:17
+ |
+LL | let error = 255i8; //~WARNING literal out of range for i8
+ | ^^^^^
+ |
+ = note: #[warn(overflowing_literals)] on by default
+
+warning: literal out of range for i8
+ --> $DIR/type-overflow.rs:21:16
+ |
+LL | let fail = 0b1000_0001i8; //~WARNING literal out of range for i8
+ | ^^^^^^^^^^^^^ help: consider using `u8` instead: `0b1000_0001u8`
+ |
+ = note: the literal `0b1000_0001i8` (decimal `129`) does not fit into an `i8` and will become `-127i8`
+
+warning: literal out of range for i64
+ --> $DIR/type-overflow.rs:23:16
+ |
+LL | let fail = 0x8000_0000_0000_0000i64; //~WARNING literal out of range for i64
+ | ^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `u64` instead: `0x8000_0000_0000_0000u64`
+ |
+ = note: the literal `0x8000_0000_0000_0000i64` (decimal `9223372036854775808`) does not fit into an `i64` and will become `-9223372036854775808i64`
+
+warning: literal out of range for u32
+ --> $DIR/type-overflow.rs:25:16
+ |
+LL | let fail = 0x1_FFFF_FFFFu32; //~WARNING literal out of range for u32
+ | ^^^^^^^^^^^^^^^^ help: consider using `u64` instead: `0x1_FFFF_FFFFu64`
+ |
+ = note: the literal `0x1_FFFF_FFFFu32` (decimal `8589934591`) does not fit into an `u32` and will become `4294967295u32`
+
+warning: literal out of range for i128
+ --> $DIR/type-overflow.rs:27:22
+ |
+LL | let fail: i128 = 0x8000_0000_0000_0000_0000_0000_0000_0000;
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ |
+ = note: the literal `0x8000_0000_0000_0000_0000_0000_0000_0000` (decimal `170141183460469231731687303715884105728`) does not fit into an `i128` and will become `-170141183460469231731687303715884105728i128`
+ = help: consider using `u128` instead
+
+warning: literal out of range for i32
+ --> $DIR/type-overflow.rs:30:16
+ |
+LL | let fail = 0x8FFF_FFFF_FFFF_FFFE; //~WARNING literal out of range for i32
+ | ^^^^^^^^^^^^^^^^^^^^^
+ |
+ = note: the literal `0x8FFF_FFFF_FFFF_FFFE` (decimal `10376293541461622782`) does not fit into an `i32` and will become `-2i32`
+ = help: consider using `i128` instead
+
+warning: literal out of range for i8
+ --> $DIR/type-overflow.rs:32:17
+ |
+LL | let fail = -0b1111_1111i8; //~WARNING literal out of range for i8
+ | ^^^^^^^^^^^^^ help: consider using `i16` instead: `0b1111_1111i16`
+ |
+ = note: the literal `0b1111_1111i8` (decimal `255`) does not fit into an `i8` and will become `-1i8`
+