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Merge pull request #2815 from darArch/master

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Warn if non-trivial work is done inside .expect
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Oliver Schneider 2018-06-11 06:33:26 -07:00 committed by GitHub
commit 8f0edba6e9
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4 changed files with 236 additions and 28 deletions
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2
clippy_lints/src/lib.rs
View File

@ -592,6 +592,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry) {
methods::OK_EXPECT,
methods::OPTION_MAP_OR_NONE,
methods::OR_FUN_CALL,
methods::EXPECT_FUN_CALL,
methods::SEARCH_IS_SOME,
methods::SHOULD_IMPLEMENT_TRAIT,
methods::SINGLE_CHAR_PATTERN,
@ -907,6 +908,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry) {
loops::UNUSED_COLLECT,
methods::ITER_NTH,
methods::OR_FUN_CALL,
methods::EXPECT_FUN_CALL,
methods::SINGLE_CHAR_PATTERN,
misc::CMP_OWNED,
mutex_atomic::MUTEX_ATOMIC,

136
clippy_lints/src/methods.rs
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@ -7,8 +7,8 @@ use std::fmt;
use std::iter;
use syntax::ast;
use syntax::codemap::{Span, BytePos};
use crate::utils::{get_arg_name, get_trait_def_id, implements_trait, in_external_macro, in_macro, is_copy, is_self, is_self_ty,
iter_input_pats, last_path_segment, match_def_path, match_path, match_qpath, match_trait_method,
use crate::utils::{get_arg_name, get_trait_def_id, implements_trait, in_external_macro, in_macro, is_copy, is_expn_of, is_self,
is_self_ty, iter_input_pats, last_path_segment, match_def_path, match_path, match_qpath, match_trait_method,
match_type, method_chain_args, match_var, return_ty, remove_blocks, same_tys, single_segment_path, snippet,
span_lint, span_lint_and_sugg, span_lint_and_then, span_note_and_lint, walk_ptrs_ty, walk_ptrs_ty_depth};
use crate::utils::paths;
@ -329,6 +329,36 @@ declare_clippy_lint! {
"using any `*or` method with a function call, which suggests `*or_else`"
}
/// **What it does:** Checks for calls to `.expect(&format!(...))`, `.expect(foo(..))`,
/// etc., and suggests to use `unwrap_or_else` instead
///
/// **Why is this bad?** The function will always be called.
///
/// **Known problems:** If the function has side-effects, not calling it will
/// change the semantic of the program, but you shouldn't rely on that anyway.
///
/// **Example:**
/// ```rust
/// foo.expect(&format("Err {}: {}", err_code, err_msg))
/// ```
/// or
/// ```rust
/// foo.expect(format("Err {}: {}", err_code, err_msg).as_str())
/// ```
/// this can instead be written:
/// ```rust
/// foo.unwrap_or_else(|_| panic!("Err {}: {}", err_code, err_msg))
/// ```
/// or
/// ```rust
/// foo.unwrap_or_else(|_| panic!(format("Err {}: {}", err_code, err_msg).as_str()))
/// ```
declare_clippy_lint! {
pub EXPECT_FUN_CALL,
perf,
"using any `expect` method with a function call"
}
/// **What it does:** Checks for usage of `.clone()` on a `Copy` type.
///
/// **Why is this bad?** The only reason `Copy` types implement `Clone` is for
@ -657,6 +687,7 @@ impl LintPass for Pass {
RESULT_MAP_UNWRAP_OR_ELSE,
OPTION_MAP_OR_NONE,
OR_FUN_CALL,
EXPECT_FUN_CALL,
CHARS_NEXT_CMP,
CHARS_LAST_CMP,
CLONE_ON_COPY,
@ -741,6 +772,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
}
lint_or_fun_call(cx, expr, *method_span, &method_call.name.as_str(), args);
lint_expect_fun_call(cx, expr, *method_span, &method_call.name.as_str(), args);
let self_ty = cx.tables.expr_ty_adjusted(&args[0]);
if args.len() == 1 && method_call.name == "clone" {
@ -964,6 +996,106 @@ fn lint_or_fun_call(cx: &LateContext, expr: &hir::Expr, method_span: Span, name:
}
}
/// Checks for the `EXPECT_FUN_CALL` lint.
fn lint_expect_fun_call(cx: &LateContext, expr: &hir::Expr, method_span: Span, name: &str, args: &[hir::Expr]) {
fn extract_format_args(arg: &hir::Expr) -> Option<&hir::HirVec<hir::Expr>> {
if let hir::ExprAddrOf(_, ref addr_of) = arg.node {
if let hir::ExprCall(ref inner_fun, ref inner_args) = addr_of.node {
if is_expn_of(inner_fun.span, "format").is_some() && inner_args.len() == 1 {
if let hir::ExprCall(_, ref format_args) = inner_args[0].node {
return Some(format_args);
}
}
}
}
None
}
fn generate_format_arg_snippet(cx: &LateContext, a: &hir::Expr) -> String {
if let hir::ExprAddrOf(_, ref format_arg) = a.node {
if let hir::ExprMatch(ref format_arg_expr, _, _) = format_arg.node {
if let hir::ExprTup(ref format_arg_expr_tup) = format_arg_expr.node {
return snippet(cx, format_arg_expr_tup[0].span, "..").into_owned();
}
}
};
snippet(cx, a.span, "..").into_owned()
}
fn check_general_case(
cx: &LateContext,
name: &str,
method_span: Span,
self_expr: &hir::Expr,
arg: &hir::Expr,
span: Span,
) {
if name != "expect" {
return;
}
let self_type = cx.tables.expr_ty(self_expr);
let known_types = &[&paths::OPTION, &paths::RESULT];
// if not a known type, return early
if known_types.iter().all(|&k| !match_type(cx, self_type, k)) {
return;
}
// don't lint for constant values
let owner_def = cx.tcx.hir.get_parent_did(arg.id);
let promotable = cx.tcx.rvalue_promotable_map(owner_def).contains(&arg.hir_id.local_id);
if promotable {
return;
}
let closure = if match_type(cx, self_type, &paths::OPTION) { "||" } else { "|_|" };
let span_replace_word = method_span.with_hi(span.hi());
if let Some(format_args) = extract_format_args(arg) {
let args_len = format_args.len();
let args: Vec<String> = format_args
.into_iter()
.take(args_len - 1)
.map(|a| generate_format_arg_snippet(cx, a))
.collect();
let sugg = args.join(", ");
span_lint_and_sugg(
cx,
EXPECT_FUN_CALL,
span_replace_word,
&format!("use of `{}` followed by a function call", name),
"try this",
format!("unwrap_or_else({} panic!({}))", closure, sugg),
);
return;
}
let sugg: Cow<_> = snippet(cx, arg.span, "..");
span_lint_and_sugg(
cx,
EXPECT_FUN_CALL,
span_replace_word,
&format!("use of `{}` followed by a function call", name),
"try this",
format!("unwrap_or_else({} panic!({}))", closure, sugg),
);
}
if args.len() == 2 {
match args[1].node {
hir::ExprLit(_) => {},
_ => check_general_case(cx, name, method_span, &args[0], &args[1], expr.span),
}
}
}
/// Checks for the `CLONE_ON_COPY` lint.
fn lint_clone_on_copy(cx: &LateContext, expr: &hir::Expr, arg: &hir::Expr, arg_ty: Ty) {
let ty = cx.tables.expr_ty(expr);

48
tests/ui/methods.rs
View File

@ -342,6 +342,54 @@ fn or_fun_call() {
let _ = stringy.unwrap_or("".to_owned());
}
/// Checks implementation of the `EXPECT_FUN_CALL` lint
fn expect_fun_call() {
struct Foo;
impl Foo {
fn new() -> Self { Foo }
fn expect(&self, msg: &str) {
panic!("{}", msg)
}
}
let with_some = Some("value");
with_some.expect("error");
let with_none: Option<i32> = None;
with_none.expect("error");
let error_code = 123_i32;
let with_none_and_format: Option<i32> = None;
with_none_and_format.expect(&format!("Error {}: fake error", error_code));
let with_none_and_as_str: Option<i32> = None;
with_none_and_as_str.expect(format!("Error {}: fake error", error_code).as_str());
let with_ok: Result<(), ()> = Ok(());
with_ok.expect("error");
let with_err: Result<(), ()> = Err(());
with_err.expect("error");
let error_code = 123_i32;
let with_err_and_format: Result<(), ()> = Err(());
with_err_and_format.expect(&format!("Error {}: fake error", error_code));
let with_err_and_as_str: Result<(), ()> = Err(());
with_err_and_as_str.expect(format!("Error {}: fake error", error_code).as_str());
let with_dummy_type = Foo::new();
with_dummy_type.expect("another test string");
let with_dummy_type_and_format = Foo::new();
with_dummy_type_and_format.expect(&format!("Error {}: fake error", error_code));
let with_dummy_type_and_as_str = Foo::new();
with_dummy_type_and_as_str.expect(format!("Error {}: fake error", error_code).as_str());
}
/// Checks implementation of `ITER_NTH` lint
fn iter_nth() {
let mut some_vec = vec![0, 1, 2, 3];

78
tests/ui/methods.stderr
View File

@ -423,83 +423,109 @@ error: use of `unwrap_or` followed by a function call
342 | let _ = stringy.unwrap_or("".to_owned());
| ^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `unwrap_or_else(|| "".to_owned())`
error: called `.iter().nth()` on a Vec. Calling `.get()` is both faster and more readable
--> $DIR/methods.rs:353:23
error: use of `expect` followed by a function call
--> $DIR/methods.rs:365:26
|
353 | let bad_vec = some_vec.iter().nth(3);
365 | with_none_and_format.expect(&format!("Error {}: fake error", error_code));
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `unwrap_or_else(|| panic!("Error {}: fake error", error_code))`
|
= note: `-D expect-fun-call` implied by `-D warnings`
error: use of `expect` followed by a function call
--> $DIR/methods.rs:368:26
|
368 | with_none_and_as_str.expect(format!("Error {}: fake error", error_code).as_str());
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `unwrap_or_else(|| panic!(format!("Error {}: fake error", error_code).as_str()))`
error: use of `expect` followed by a function call
--> $DIR/methods.rs:378:25
|
378 | with_err_and_format.expect(&format!("Error {}: fake error", error_code));
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `unwrap_or_else(|_| panic!("Error {}: fake error", error_code))`
error: use of `expect` followed by a function call
--> $DIR/methods.rs:381:25
|
381 | with_err_and_as_str.expect(format!("Error {}: fake error", error_code).as_str());
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `unwrap_or_else(|_| panic!(format!("Error {}: fake error", error_code).as_str()))`
error: called `.iter().nth()` on a Vec. Calling `.get()` is both faster and more readable
--> $DIR/methods.rs:401:23
|
401 | let bad_vec = some_vec.iter().nth(3);
| ^^^^^^^^^^^^^^^^^^^^^^
|
= note: `-D iter-nth` implied by `-D warnings`
error: called `.iter().nth()` on a slice. Calling `.get()` is both faster and more readable
--> $DIR/methods.rs:354:26
--> $DIR/methods.rs:402:26
|
354 | let bad_slice = &some_vec[..].iter().nth(3);
402 | let bad_slice = &some_vec[..].iter().nth(3);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^
error: called `.iter().nth()` on a slice. Calling `.get()` is both faster and more readable
--> $DIR/methods.rs:355:31
--> $DIR/methods.rs:403:31
|
355 | let bad_boxed_slice = boxed_slice.iter().nth(3);
403 | let bad_boxed_slice = boxed_slice.iter().nth(3);
| ^^^^^^^^^^^^^^^^^^^^^^^^^
error: called `.iter().nth()` on a VecDeque. Calling `.get()` is both faster and more readable
--> $DIR/methods.rs:356:29
--> $DIR/methods.rs:404:29
|
356 | let bad_vec_deque = some_vec_deque.iter().nth(3);
404 | let bad_vec_deque = some_vec_deque.iter().nth(3);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: called `.iter_mut().nth()` on a Vec. Calling `.get_mut()` is both faster and more readable
--> $DIR/methods.rs:361:23
--> $DIR/methods.rs:409:23
|
361 | let bad_vec = some_vec.iter_mut().nth(3);
409 | let bad_vec = some_vec.iter_mut().nth(3);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^
error: called `.iter_mut().nth()` on a slice. Calling `.get_mut()` is both faster and more readable
--> $DIR/methods.rs:364:26
--> $DIR/methods.rs:412:26
|
364 | let bad_slice = &some_vec[..].iter_mut().nth(3);
412 | let bad_slice = &some_vec[..].iter_mut().nth(3);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: called `.iter_mut().nth()` on a VecDeque. Calling `.get_mut()` is both faster and more readable
--> $DIR/methods.rs:367:29
--> $DIR/methods.rs:415:29
|
367 | let bad_vec_deque = some_vec_deque.iter_mut().nth(3);
415 | let bad_vec_deque = some_vec_deque.iter_mut().nth(3);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: called `skip(x).next()` on an iterator. This is more succinctly expressed by calling `nth(x)`
--> $DIR/methods.rs:379:13
--> $DIR/methods.rs:427:13
|
379 | let _ = some_vec.iter().skip(42).next();
427 | let _ = some_vec.iter().skip(42).next();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: `-D iter-skip-next` implied by `-D warnings`
error: called `skip(x).next()` on an iterator. This is more succinctly expressed by calling `nth(x)`
--> $DIR/methods.rs:380:13
--> $DIR/methods.rs:428:13
|
380 | let _ = some_vec.iter().cycle().skip(42).next();
428 | let _ = some_vec.iter().cycle().skip(42).next();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: called `skip(x).next()` on an iterator. This is more succinctly expressed by calling `nth(x)`
--> $DIR/methods.rs:381:13
--> $DIR/methods.rs:429:13
|
381 | let _ = (1..10).skip(10).next();
429 | let _ = (1..10).skip(10).next();
| ^^^^^^^^^^^^^^^^^^^^^^^
error: called `skip(x).next()` on an iterator. This is more succinctly expressed by calling `nth(x)`
--> $DIR/methods.rs:382:14
--> $DIR/methods.rs:430:14
|
382 | let _ = &some_vec[..].iter().skip(3).next();
430 | let _ = &some_vec[..].iter().skip(3).next();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: used unwrap() on an Option value. If you don't want to handle the None case gracefully, consider using expect() to provide a better panic message
--> $DIR/methods.rs:391:13
--> $DIR/methods.rs:439:13
|
391 | let _ = opt.unwrap();
439 | let _ = opt.unwrap();
| ^^^^^^^^^^^^
|
= note: `-D option-unwrap-used` implied by `-D warnings`
error: aborting due to 66 previous errors
error: aborting due to 70 previous errors