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try_err: Consider Try impl for Poll when generating suggestions

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There are two different implementation of Try trait for Poll type;
Poll<Result<T, E>> and Poll<Option<Result<T, E>>>. Take them into
account when generating suggestions.

For example, for Err(e)? suggest either return Poll::Ready(Err(e)) or
return Poll::Ready(Some(Err(e))) as appropriate.
This commit is contained in:
Tomasz Miąsko 2020-08-02 00:00:00 +00:00
parent bbbc973a84
commit e9677105bf
5 changed files with 155 additions and 31 deletions
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112
clippy_lints/src/try_err.rs
View File

@ -1,10 +1,13 @@
use crate::utils::{match_qpath, paths, snippet, snippet_with_macro_callsite, span_lint_and_sugg};
use crate::utils::{
is_type_diagnostic_item, match_def_path, match_qpath, paths, snippet, snippet_with_macro_callsite,
span_lint_and_sugg,
};
use if_chain::if_chain;
use rustc_errors::Applicability;
use rustc_hir::{Arm, Expr, ExprKind, MatchSource};
use rustc_hir::{Expr, ExprKind, MatchSource};
use rustc_lint::{LateContext, LateLintPass};
use rustc_middle::lint::in_external_macro;
use rustc_middle::ty::Ty;
use rustc_middle::ty::{self, Ty};
use rustc_session::{declare_lint_pass, declare_tool_lint};
declare_clippy_lint! {
@ -65,19 +68,39 @@ fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
if let Some(ref err_arg) = err_args.get(0);
if let ExprKind::Path(ref err_fun_path) = err_fun.kind;
if match_qpath(err_fun_path, &paths::RESULT_ERR);
if let Some(return_type) = find_err_return_type(cx, &expr.kind);
if let Some(return_ty) = find_return_type(cx, &expr.kind);
then {
let err_type = cx.typeck_results().expr_ty(err_arg);
let prefix;
let suffix;
let err_ty;
if let Some(ty) = result_error_type(cx, return_ty) {
prefix = "Err(";
suffix = ")";
err_ty = ty;
} else if let Some(ty) = poll_result_error_type(cx, return_ty) {
prefix = "Poll::Ready(Err(";
suffix = "))";
err_ty = ty;
} else if let Some(ty) = poll_option_result_error_type(cx, return_ty) {
prefix = "Poll::Ready(Some(Err(";
suffix = ")))";
err_ty = ty;
} else {
return;
};
let expr_err_ty = cx.typeck_results().expr_ty(err_arg);
let origin_snippet = if err_arg.span.from_expansion() {
snippet_with_macro_callsite(cx, err_arg.span, "_")
} else {
snippet(cx, err_arg.span, "_")
};
let suggestion = if err_type == return_type {
format!("return Err({})", origin_snippet)
let suggestion = if err_ty == expr_err_ty {
format!("return {}{}{}", prefix, origin_snippet, suffix)
} else {
format!("return Err({}.into())", origin_snippet)
format!("return {}{}.into(){}", prefix, origin_snippet, suffix)
};
span_lint_and_sugg(
@ -94,27 +117,68 @@ fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
}
}
// In order to determine whether to suggest `.into()` or not, we need to find the error type the
// function returns. To do that, we look for the From::from call (see tree above), and capture
// its output type.
fn find_err_return_type<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx ExprKind<'_>) -> Option<Ty<'tcx>> {
/// Finds function return type by examining return expressions in match arms.
fn find_return_type<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx ExprKind<'_>) -> Option<Ty<'tcx>> {
if let ExprKind::Match(_, ref arms, MatchSource::TryDesugar) = expr {
arms.iter().find_map(|ty| find_err_return_type_arm(cx, ty))
} else {
None
for arm in arms.iter() {
if let ExprKind::Ret(Some(ref ret)) = arm.body.kind {
return Some(cx.typeck_results().expr_ty(ret));
}
}
}
None
}
// Check for From::from in one of the match arms.
fn find_err_return_type_arm<'tcx>(cx: &LateContext<'tcx>, arm: &'tcx Arm<'_>) -> Option<Ty<'tcx>> {
/// Extracts the error type from Result<T, E>.
fn result_error_type<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> Option<Ty<'tcx>> {
if_chain! {
if let ExprKind::Ret(Some(ref err_ret)) = arm.body.kind;
if let ExprKind::Call(ref from_error_path, ref from_error_args) = err_ret.kind;
if let ExprKind::Path(ref from_error_fn) = from_error_path.kind;
if match_qpath(from_error_fn, &paths::TRY_FROM_ERROR);
if let Some(from_error_arg) = from_error_args.get(0);
if let ty::Adt(_, subst) = ty.kind;
if is_type_diagnostic_item(cx, ty, sym!(result_type));
let err_ty = subst.type_at(1);
then {
Some(cx.typeck_results().expr_ty(from_error_arg))
Some(err_ty)
} else {
None
}
}
}
/// Extracts the error type from Poll<Result<T, E>>.
fn poll_result_error_type<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> Option<Ty<'tcx>> {
if_chain! {
if let ty::Adt(def, subst) = ty.kind;
if match_def_path(cx, def.did, &paths::POLL);
let ready_ty = subst.type_at(0);
if let ty::Adt(ready_def, ready_subst) = ready_ty.kind;
if cx.tcx.is_diagnostic_item(sym!(result_type), ready_def.did);
let err_ty = ready_subst.type_at(1);
then {
Some(err_ty)
} else {
None
}
}
}
/// Extracts the error type from Poll<Option<Result<T, E>>>.
fn poll_option_result_error_type<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> Option<Ty<'tcx>> {
if_chain! {
if let ty::Adt(def, subst) = ty.kind;
if match_def_path(cx, def.did, &paths::POLL);
let ready_ty = subst.type_at(0);
if let ty::Adt(ready_def, ready_subst) = ready_ty.kind;
if cx.tcx.is_diagnostic_item(sym!(option_type), ready_def.did);
let some_ty = ready_subst.type_at(0);
if let ty::Adt(some_def, some_subst) = some_ty.kind;
if cx.tcx.is_diagnostic_item(sym!(result_type), some_def.did);
let err_ty = some_subst.type_at(1);
then {
Some(err_ty)
} else {
None
}

2
clippy_lints/src/utils/paths.rs
View File

@ -80,6 +80,7 @@
pub const PATH_BUF: [&str; 3] = ["std", "path", "PathBuf"];
pub const PATH_BUF_AS_PATH: [&str; 4] = ["std", "path", "PathBuf", "as_path"];
pub const PATH_TO_PATH_BUF: [&str; 4] = ["std", "path", "Path", "to_path_buf"];
pub const POLL: [&str; 4] = ["core", "task", "poll", "Poll"];
pub const PTR_EQ: [&str; 3] = ["core", "ptr", "eq"];
pub const PTR_NULL: [&str; 2] = ["ptr", "null"];
pub const PTR_NULL_MUT: [&str; 2] = ["ptr", "null_mut"];
@ -129,7 +130,6 @@
pub const TO_STRING_METHOD: [&str; 4] = ["alloc", "string", "ToString", "to_string"];
pub const TRANSMUTE: [&str; 4] = ["core", "intrinsics", "", "transmute"];
pub const TRY_FROM: [&str; 4] = ["core", "convert", "TryFrom", "try_from"];
pub const TRY_FROM_ERROR: [&str; 4] = ["std", "ops", "Try", "from_error"];
pub const TRY_INTO_RESULT: [&str; 4] = ["std", "ops", "Try", "into_result"];
pub const TRY_INTO_TRAIT: [&str; 3] = ["core", "convert", "TryInto"];
pub const VEC: [&str; 3] = ["alloc", "vec", "Vec"];

21
tests/ui/try_err.fixed
View File

@ -6,6 +6,9 @@
#[macro_use]
extern crate macro_rules;
use std::io;
use std::task::Poll;
// Tests that a simple case works
// Should flag `Err(err)?`
pub fn basic_test() -> Result<i32, i32> {
@ -104,3 +107,21 @@ pub fn macro_inside(fail: bool) -> Result<i32, String> {
}
Ok(0)
}
pub fn poll_write(n: usize) -> Poll<io::Result<usize>> {
if n == 0 {
return Poll::Ready(Err(io::ErrorKind::WriteZero.into()))
} else if n == 1 {
return Poll::Ready(Err(io::Error::new(io::ErrorKind::InvalidInput, "error")))
};
Poll::Ready(Ok(n))
}
pub fn poll_next(ready: bool) -> Poll<Option<io::Result<()>>> {
if !ready {
return Poll::Ready(Some(Err(io::ErrorKind::NotFound.into())))
}
Poll::Ready(None)
}

21
tests/ui/try_err.rs
View File

@ -6,6 +6,9 @@
#[macro_use]
extern crate macro_rules;
use std::io;
use std::task::Poll;
// Tests that a simple case works
// Should flag `Err(err)?`
pub fn basic_test() -> Result<i32, i32> {
@ -104,3 +107,21 @@ pub fn macro_inside(fail: bool) -> Result<i32, String> {
}
Ok(0)
}
pub fn poll_write(n: usize) -> Poll<io::Result<usize>> {
if n == 0 {
Err(io::ErrorKind::WriteZero)?
} else if n == 1 {
Err(io::Error::new(io::ErrorKind::InvalidInput, "error"))?
};
Poll::Ready(Ok(n))
}
pub fn poll_next(ready: bool) -> Poll<Option<io::Result<()>>> {
if !ready {
Err(io::ErrorKind::NotFound)?
}
Poll::Ready(None)
}

30
tests/ui/try_err.stderr
View File

@ -1,5 +1,5 @@
error: returning an `Err(_)` with the `?` operator
--> $DIR/try_err.rs:15:9
--> $DIR/try_err.rs:18:9
|
LL | Err(err)?;
| ^^^^^^^^^ help: try this: `return Err(err)`
@ -11,28 +11,46 @@ LL | #![deny(clippy::try_err)]
| ^^^^^^^^^^^^^^^
error: returning an `Err(_)` with the `?` operator
--> $DIR/try_err.rs:25:9
--> $DIR/try_err.rs:28:9
|
LL | Err(err)?;
| ^^^^^^^^^ help: try this: `return Err(err.into())`
error: returning an `Err(_)` with the `?` operator
--> $DIR/try_err.rs:45:17
--> $DIR/try_err.rs:48:17
|
LL | Err(err)?;
| ^^^^^^^^^ help: try this: `return Err(err)`
error: returning an `Err(_)` with the `?` operator
--> $DIR/try_err.rs:64:17
--> $DIR/try_err.rs:67:17
|
LL | Err(err)?;
| ^^^^^^^^^ help: try this: `return Err(err.into())`
error: returning an `Err(_)` with the `?` operator
--> $DIR/try_err.rs:103:9
--> $DIR/try_err.rs:106:9
|
LL | Err(foo!())?;
| ^^^^^^^^^^^^ help: try this: `return Err(foo!())`
error: aborting due to 5 previous errors
error: returning an `Err(_)` with the `?` operator
--> $DIR/try_err.rs:113:9
|
LL | Err(io::ErrorKind::WriteZero)?
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `return Poll::Ready(Err(io::ErrorKind::WriteZero.into()))`
error: returning an `Err(_)` with the `?` operator
--> $DIR/try_err.rs:115:9
|
LL | Err(io::Error::new(io::ErrorKind::InvalidInput, "error"))?
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `return Poll::Ready(Err(io::Error::new(io::ErrorKind::InvalidInput, "error")))`
error: returning an `Err(_)` with the `?` operator
--> $DIR/try_err.rs:123:9
|
LL | Err(io::ErrorKind::NotFound)?
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `return Poll::Ready(Some(Err(io::ErrorKind::NotFound.into())))`
error: aborting due to 8 previous errors