lint unportable clike enum discriminants

README.md

@@ -8,7 +8,7 @@ A collection of lints to catch common mistakes and improve your Rust code.
 [Jump to usage instructions](#usage)
 
 ##Lints
-There are 127 lints included in this crate:
+There are 128 lints included in this crate:
 
 name                                                                                                                 | default | meaning
 ---------------------------------------------------------------------------------------------------------------------|---------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
@@ -38,6 +38,7 @@ name
 [drop_ref](https://github.com/Manishearth/rust-clippy/wiki#drop_ref)                                                 | warn    | call to `std::mem::drop` with a reference instead of an owned value, which will not call the `Drop::drop` method on the underlying value
 [duplicate_underscore_argument](https://github.com/Manishearth/rust-clippy/wiki#duplicate_underscore_argument)       | warn    | Function arguments having names which only differ by an underscore
 [empty_loop](https://github.com/Manishearth/rust-clippy/wiki#empty_loop)                                             | warn    | empty `loop {}` detected
+[enum_clike_unportable_variant](https://github.com/Manishearth/rust-clippy/wiki#enum_clike_unportable_variant)       | warn    | finds C-like enums that are `repr(isize/usize)` and have values that don't fit into an `i32`
 [enum_glob_use](https://github.com/Manishearth/rust-clippy/wiki#enum_glob_use)                                       | allow   | finds use items that import all variants of an enum
 [enum_variant_names](https://github.com/Manishearth/rust-clippy/wiki#enum_variant_names)                             | warn    | finds enums where all variants share a prefix/postfix
 [eq_op](https://github.com/Manishearth/rust-clippy/wiki#eq_op)                                                       | warn    | equal operands on both sides of a comparison or bitwise combination (e.g. `x == x`)

src/enum_clike.rs

@@ -0,0 +1,56 @@
+//! lint on C-like enums that are `repr(isize/usize)` and have values that don't fit into an `i32`
+
+use rustc::lint::*;
+use syntax::ast::{IntTy, UintTy};
+use syntax::attr::*;
+use rustc_front::hir::*;
+use rustc::middle::const_eval::{ConstVal, EvalHint, eval_const_expr_partial};
+use rustc::middle::ty;
+use utils::span_lint;
+
+/// **What it does:** Lints on C-like enums that are `repr(isize/usize)` and have values that don't fit into an `i32`.
+///
+/// **Why is this bad?** This will truncate the variant value on 32bit architectures, but works fine on 64 bit.
+///
+/// **Known problems:** None
+///
+/// **Example:** `#[repr(usize)] enum NonPortable { X = 0x1_0000_0000, Y = 0 }`
+declare_lint! {
+    pub ENUM_CLIKE_UNPORTABLE_VARIANT, Warn,
+    "finds C-like enums that are `repr(isize/usize)` and have values that don't fit into an `i32`"
+}
+
+pub struct EnumClikeUnportableVariant;
+
+impl LintPass for EnumClikeUnportableVariant {
+    fn get_lints(&self) -> LintArray {
+        lint_array!(ENUM_CLIKE_UNPORTABLE_VARIANT)
+    }
+}
+
+impl LateLintPass for EnumClikeUnportableVariant {
+    #[allow(cast_possible_truncation, cast_sign_loss)]
+    fn check_item(&mut self, cx: &LateContext, item: &Item) {
+        if let ItemEnum(ref def, _) = item.node {
+            for var in &def.variants {
+                let variant = &var.node;
+                if let Some(ref disr) = variant.disr_expr {
+                    let cv = eval_const_expr_partial(cx.tcx, &**disr, EvalHint::ExprTypeChecked, None);
+                    let bad = match (cv, &cx.tcx.expr_ty(&**disr).sty) {
+                        (Ok(ConstVal::Int(i)), &ty::TyInt(IntTy::Is)) => i as i32 as i64 != i,
+                        (Ok(ConstVal::Uint(i)), &ty::TyInt(IntTy::Is)) => i as i32 as u64 != i,
+                        (Ok(ConstVal::Int(i)), &ty::TyUint(UintTy::Us)) => (i < 0) || (i as u32 as i64 != i),
+                        (Ok(ConstVal::Uint(i)), &ty::TyUint(UintTy::Us)) => i as u32 as u64 != i,
+                        _ => false,
+                    };
+                    if bad {
+                        span_lint(cx,
+                                  ENUM_CLIKE_UNPORTABLE_VARIANT,
+                                  var.span,
+                                  "Clike enum variant discriminant is not portable to 32-bit targets");
+                    }
+                }
+            }
+        }
+    }
+}

src/lib.rs

@@ -51,6 +51,7 @@ pub mod cyclomatic_complexity;
 pub mod derive;
 pub mod drop_ref;
 pub mod entry;
+pub mod enum_clike;
 pub mod enum_glob_use;
 pub mod enum_variants;
 pub mod eq_op;
@@ -108,6 +109,7 @@ pub fn plugin_registrar(reg: &mut Registry) {
     reg.register_late_lint_pass(box eq_op::EqOp);
     reg.register_early_lint_pass(box enum_variants::EnumVariantNames);
     reg.register_late_lint_pass(box enum_glob_use::EnumGlobUse);
+    reg.register_late_lint_pass(box enum_clike::EnumClikeUnportableVariant);
     reg.register_late_lint_pass(box bit_mask::BitMask);
     reg.register_late_lint_pass(box ptr_arg::PtrArg);
     reg.register_late_lint_pass(box needless_bool::NeedlessBool);
@@ -211,6 +213,7 @@ pub fn plugin_registrar(reg: &mut Registry) {
         derive::EXPL_IMPL_CLONE_ON_COPY,
         drop_ref::DROP_REF,
         entry::MAP_ENTRY,
+        enum_clike::ENUM_CLIKE_UNPORTABLE_VARIANT,
         enum_variants::ENUM_VARIANT_NAMES,
         eq_op::EQ_OP,
         escape::BOXED_LOCAL,

tests/compile-fail/enums_clike.rs

@@ -0,0 +1,53 @@
+#![feature(plugin, associated_consts)]
+#![plugin(clippy)]
+#![deny(clippy)]
+
+#![allow(unused)]
+
+#[repr(usize)]
+enum NonPortable {
+    X = 0x1_0000_0000, //~ ERROR: Clike enum variant discriminant is not portable to 32-bit targets
+    Y = 0,
+    Z = 0x7FFF_FFFF,
+    A = 0xFFFF_FFFF,
+}
+
+enum NonPortableNoHint {
+    X = 0x1_0000_0000, //~ ERROR: Clike enum variant discriminant is not portable to 32-bit targets
+    Y = 0,
+    Z = 0x7FFF_FFFF,
+    A = 0xFFFF_FFFF, //~ ERROR: Clike enum variant discriminant is not portable to 32-bit targets
+}
+
+#[repr(isize)]
+enum NonPortableSigned {
+    X = -1,
+    Y = 0x7FFF_FFFF,
+    Z = 0xFFFF_FFFF, //~ ERROR: Clike enum variant discriminant is not portable to 32-bit targets
+    A = 0x1_0000_0000, //~ ERROR: Clike enum variant discriminant is not portable to 32-bit targets
+    B = std::i32::MIN as isize,
+    C = (std::i32::MIN as isize) - 1, //~ ERROR: Clike enum variant discriminant is not portable to 32-bit targets
+}
+
+enum NonPortableSignedNoHint {
+    X = -1,
+    Y = 0x7FFF_FFFF,
+    Z = 0xFFFF_FFFF, //~ ERROR: Clike enum variant discriminant is not portable to 32-bit targets
+    A = 0x1_0000_0000, //~ ERROR: Clike enum variant discriminant is not portable to 32-bit targets
+}
+
+/*
+FIXME: uncomment once https://github.com/rust-lang/rust/issues/31910 is fixed
+#[repr(usize)]
+enum NonPortable2<T: Trait> {
+    X = Trait::Number,
+    Y = 0,
+}
+
+trait Trait {
+    const Number: usize = 0x1_0000_0000;
+}
+*/
+
+fn main() {
+}