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Merge pull request #2143 from HMPerson1/master 

Add lint for fallible impls of `From`
This commit is contained in:
Oliver Schneider 2017-10-23 09:21:31 +02:00 committed by GitHub
parent 6d89798119 7206023b1b
commit b96639f23a
5 changed files with 290 additions and 0 deletions
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130
clippy_lints/src/fallible_impl_from.rs Normal file
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@ -0,0 +1,130 @@
use rustc::lint::*;
use rustc::hir;
use rustc::ty;
use syntax_pos::Span;
use utils::{method_chain_args, match_def_path, span_lint_and_then, walk_ptrs_ty};
use utils::paths::{BEGIN_PANIC, BEGIN_PANIC_FMT, FROM_TRAIT, OPTION, RESULT};
/// **What it does:** Checks for impls of `From<..>` that contain `panic!()` or `unwrap()`
///
/// **Why is this bad?** `TryFrom` should be used if there's a possibility of failure.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// struct Foo(i32);
/// impl From<String> for Foo {
/// fn from(s: String) -> Self {
/// Foo(s.parse().unwrap())
/// }
/// }
/// ```
declare_lint! {
pub FALLIBLE_IMPL_FROM, Allow,
"Warn on impls of `From<..>` that contain `panic!()` or `unwrap()`"
}
pub struct FallibleImplFrom;
impl LintPass for FallibleImplFrom {
fn get_lints(&self) -> LintArray {
lint_array!(FALLIBLE_IMPL_FROM)
}
}
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for FallibleImplFrom {
fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx hir::Item) {
// check for `impl From<???> for ..`
let impl_def_id = cx.tcx.hir.local_def_id(item.id);
if_let_chain!{[
let hir::ItemImpl(.., ref impl_items) = item.node,
let Some(impl_trait_ref) = cx.tcx.impl_trait_ref(impl_def_id),
match_def_path(cx.tcx, impl_trait_ref.def_id, &FROM_TRAIT),
], {
lint_impl_body(cx, item.span, impl_items);
}}
}
}
fn lint_impl_body<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, impl_span: Span, impl_items: &hir::HirVec<hir::ImplItemRef>) {
use rustc::hir::*;
use rustc::hir::intravisit::{self, NestedVisitorMap, Visitor};
struct FindPanicUnwrap<'a, 'tcx: 'a> {
tcx: ty::TyCtxt<'a, 'tcx, 'tcx>,
tables: &'tcx ty::TypeckTables<'tcx>,
result: Vec<Span>,
}
impl<'a, 'tcx: 'a> Visitor<'tcx> for FindPanicUnwrap<'a, 'tcx> {
fn visit_expr(&mut self, expr: &'tcx Expr) {
// check for `begin_panic`
if_let_chain!{[
let ExprCall(ref func_expr, _) = expr.node,
let ExprPath(QPath::Resolved(_, ref path)) = func_expr.node,
match_def_path(self.tcx, path.def.def_id(), &BEGIN_PANIC) ||
match_def_path(self.tcx, path.def.def_id(), &BEGIN_PANIC_FMT),
], {
self.result.push(expr.span);
}}
// check for `unwrap`
if let Some(arglists) = method_chain_args(expr, &["unwrap"]) {
let reciever_ty = walk_ptrs_ty(self.tables.expr_ty(&arglists[0][0]));
if match_type(self.tcx, reciever_ty, &OPTION) ||
match_type(self.tcx, reciever_ty, &RESULT)
{
self.result.push(expr.span);
}
}
// and check sub-expressions
intravisit::walk_expr(self, expr);
}
fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
NestedVisitorMap::None
}
}
for impl_item in impl_items {
if_let_chain!{[
impl_item.name == "from",
let ImplItemKind::Method(_, body_id) =
cx.tcx.hir.impl_item(impl_item.id).node,
], {
// check the body for `begin_panic` or `unwrap`
let body = cx.tcx.hir.body(body_id);
let impl_item_def_id = cx.tcx.hir.local_def_id(impl_item.id.node_id);
let mut fpu = FindPanicUnwrap {
tcx: cx.tcx,
tables: cx.tcx.typeck_tables_of(impl_item_def_id),
result: Vec::new(),
};
fpu.visit_expr(&body.value);
// if we've found one, lint
if !fpu.result.is_empty() {
span_lint_and_then(
cx,
FALLIBLE_IMPL_FROM,
impl_span,
"consider implementing `TryFrom` instead",
move |db| {
db.help(
"`From` is intended for infallible conversions only. \
Use `TryFrom` if there's a possibility for the conversion to fail.");
db.span_note(fpu.result, "potential failure(s)");
});
}
}}
}
}
fn match_type(tcx: ty::TyCtxt, ty: ty::Ty, path: &[&str]) -> bool {
match ty.sty {
ty::TyAdt(adt, _) => match_def_path(tcx, adt.did, path),
_ => false,
}
}

3
clippy_lints/src/lib.rs
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@ -100,6 +100,7 @@ pub mod identity_conversion;
pub mod identity_op;
pub mod if_let_redundant_pattern_matching;
pub mod if_not_else;
pub mod fallible_impl_from;
pub mod infinite_iter;
pub mod int_plus_one;
pub mod invalid_ref;
@ -341,6 +342,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry) {
reg.register_late_lint_pass(box identity_conversion::IdentityConversion::default());
reg.register_late_lint_pass(box types::ImplicitHasher);
reg.register_early_lint_pass(box const_static_lifetime::StaticConst);
reg.register_late_lint_pass(box fallible_impl_from::FallibleImplFrom);
reg.register_lint_group("clippy_restrictions", vec![
arithmetic::FLOAT_ARITHMETIC,
@ -446,6 +448,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry) {
identity_conversion::IDENTITY_CONVERSION,
identity_op::IDENTITY_OP,
if_let_redundant_pattern_matching::IF_LET_REDUNDANT_PATTERN_MATCHING,
fallible_impl_from::FALLIBLE_IMPL_FROM,
infinite_iter::INFINITE_ITER,
invalid_ref::INVALID_REF,
is_unit_expr::UNIT_EXPR,

2
clippy_lints/src/utils/paths.rs
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@ -6,6 +6,7 @@ pub const ARC: [&str; 3] = ["alloc", "arc", "Arc"];
pub const ASMUT_TRAIT: [&str; 3] = ["core", "convert", "AsMut"];
pub const ASREF_TRAIT: [&str; 3] = ["core", "convert", "AsRef"];
pub const BEGIN_PANIC: [&str; 3] = ["std", "panicking", "begin_panic"];
pub const BEGIN_PANIC_FMT: [&str; 3] = ["std", "panicking", "begin_panic_fmt"];
pub const BINARY_HEAP: [&str; 3] = ["alloc", "binary_heap", "BinaryHeap"];
pub const BORROW_TRAIT: [&str; 3] = ["core", "borrow", "Borrow"];
pub const BOX: [&str; 3] = ["std", "boxed", "Box"];
@ -27,6 +28,7 @@ pub const DROP: [&str; 3] = ["core", "mem", "drop"];
pub const FMT_ARGUMENTS_NEWV1: [&str; 4] = ["core", "fmt", "Arguments", "new_v1"];
pub const FMT_ARGUMENTV1_NEW: [&str; 4] = ["core", "fmt", "ArgumentV1", "new"];
pub const FROM_FROM: [&str; 4] = ["core", "convert", "From", "from"];
pub const FROM_TRAIT: [&str; 3] = ["core", "convert", "From"];
pub const HASH: [&str; 2] = ["hash", "Hash"];
pub const HASHMAP: [&str; 5] = ["std", "collections", "hash", "map", "HashMap"];
pub const HASHMAP_ENTRY: [&str; 5] = ["std", "collections", "hash", "map", "Entry"];

64
tests/ui/fallible_impl_from.rs Normal file
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@ -0,0 +1,64 @@
#![deny(fallible_impl_from)]
// docs example
struct Foo(i32);
impl From<String> for Foo {
fn from(s: String) -> Self {
Foo(s.parse().unwrap())
}
}
struct Valid(Vec<u8>);
impl<'a> From<&'a str> for Valid {
fn from(s: &'a str) -> Valid {
Valid(s.to_owned().into_bytes())
}
}
impl From<usize> for Valid {
fn from(i: usize) -> Valid {
Valid(Vec::with_capacity(i))
}
}
struct Invalid;
impl From<usize> for Invalid {
fn from(i: usize) -> Invalid {
if i != 42 {
panic!();
}
Invalid
}
}
impl From<Option<String>> for Invalid {
fn from(s: Option<String>) -> Invalid {
let s = s.unwrap();
if !s.is_empty() {
panic!(42);
} else if s.parse::<u32>().unwrap() != 42 {
panic!("{:?}", s);
}
Invalid
}
}
trait ProjStrTrait {
type ProjString;
}
impl<T> ProjStrTrait for Box<T> {
type ProjString = String;
}
impl<'a> From<&'a mut <Box<u32> as ProjStrTrait>::ProjString> for Invalid {
fn from(s: &'a mut <Box<u32> as ProjStrTrait>::ProjString) -> Invalid {
if s.parse::<u32>().ok().unwrap() != 42 {
panic!("{:?}", s);
}
Invalid
}
}
fn main() {}

91
tests/ui/fallible_impl_from.stderr Normal file
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@ -0,0 +1,91 @@
error: consider implementing `TryFrom` instead
--> $DIR/fallible_impl_from.rs:5:1
|
5 | / impl From<String> for Foo {
6 | | fn from(s: String) -> Self {
7 | | Foo(s.parse().unwrap())
8 | | }
9 | | }
| |_^
|
note: lint level defined here
--> $DIR/fallible_impl_from.rs:1:9
|
1 | #![deny(fallible_impl_from)]
| ^^^^^^^^^^^^^^^^^^
= help: `From` is intended for infallible conversions only. Use `TryFrom` if there's a possibility for the conversion to fail.
note: potential failure(s)
--> $DIR/fallible_impl_from.rs:7:13
|
7 | Foo(s.parse().unwrap())
| ^^^^^^^^^^^^^^^^^^
error: consider implementing `TryFrom` instead
--> $DIR/fallible_impl_from.rs:28:1
|
28 | / impl From<usize> for Invalid {
29 | | fn from(i: usize) -> Invalid {
30 | | if i != 42 {
31 | | panic!();
... |
34 | | }
35 | | }
| |_^
|
= help: `From` is intended for infallible conversions only. Use `TryFrom` if there's a possibility for the conversion to fail.
note: potential failure(s)
--> $DIR/fallible_impl_from.rs:31:13
|
31 | panic!();
| ^^^^^^^^^
= note: this error originates in a macro outside of the current crate
error: consider implementing `TryFrom` instead
--> $DIR/fallible_impl_from.rs:37:1
|
37 | / impl From<Option<String>> for Invalid {
38 | | fn from(s: Option<String>) -> Invalid {
39 | | let s = s.unwrap();
40 | | if !s.is_empty() {
... |
46 | | }
47 | | }
| |_^
|
= help: `From` is intended for infallible conversions only. Use `TryFrom` if there's a possibility for the conversion to fail.
note: potential failure(s)
--> $DIR/fallible_impl_from.rs:39:17
|
39 | let s = s.unwrap();
| ^^^^^^^^^^
40 | if !s.is_empty() {
41 | panic!(42);
| ^^^^^^^^^^^
42 | } else if s.parse::<u32>().unwrap() != 42 {
| ^^^^^^^^^^^^^^^^^^^^^^^^^
43 | panic!("{:?}", s);
| ^^^^^^^^^^^^^^^^^^
= note: this error originates in a macro outside of the current crate
error: consider implementing `TryFrom` instead
--> $DIR/fallible_impl_from.rs:55:1
|
55 | / impl<'a> From<&'a mut <Box<u32> as ProjStrTrait>::ProjString> for Invalid {
56 | | fn from(s: &'a mut <Box<u32> as ProjStrTrait>::ProjString) -> Invalid {
57 | | if s.parse::<u32>().ok().unwrap() != 42 {
58 | | panic!("{:?}", s);
... |
61 | | }
62 | | }
| |_^
|
= help: `From` is intended for infallible conversions only. Use `TryFrom` if there's a possibility for the conversion to fail.
note: potential failure(s)
--> $DIR/fallible_impl_from.rs:57:12
|
57 | if s.parse::<u32>().ok().unwrap() != 42 {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
58 | panic!("{:?}", s);
| ^^^^^^^^^^^^^^^^^^
= note: this error originates in a macro outside of the current crate