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Auto merge of #5291 - ThibsG:FixSingleBinding, r=flip1995

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Fix match single binding when in a let stmt

Fix bad suggestion when `match_single_binding` lints when inside a local (let) statement.

Fixes #5267

changelog: none
This commit is contained in:
bors 2020-03-09 16:04:26 +00:00
commit 118594ffa2
4 changed files with 84 additions and 23 deletions
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54
clippy_lints/src/matches.rs
View file

@ -14,8 +14,8 @@ use rustc_ast::ast::LitKind;
use rustc_errors::Applicability;
use rustc_hir::def::CtorKind;
use rustc_hir::{
print, Arm, BindingAnnotation, Block, BorrowKind, Expr, ExprKind, Local, MatchSource, Mutability, Pat, PatKind,
QPath, RangeEnd,
print, Arm, BindingAnnotation, Block, BorrowKind, Expr, ExprKind, Local, MatchSource, Mutability, Node, Pat,
PatKind, QPath, RangeEnd,
};
use rustc_lint::{LateContext, LateLintPass, LintContext};
use rustc_session::{declare_tool_lint, impl_lint_pass};
@ -882,7 +882,7 @@ fn check_wild_in_or_pats(cx: &LateContext<'_, '_>, arms: &[Arm<'_>]) {
}
}
fn check_match_single_binding(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr: &Expr<'_>) {
fn check_match_single_binding<'a>(cx: &LateContext<'_, 'a>, ex: &Expr<'a>, arms: &[Arm<'_>], expr: &Expr<'_>) {
if in_macro(expr.span) || arms.len() != 1 || is_refutable(cx, arms[0].pat) {
return;
}
@ -914,19 +914,38 @@ fn check_match_single_binding(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[A
let mut applicability = Applicability::MaybeIncorrect;
match arms[0].pat.kind {
PatKind::Binding(..) | PatKind::Tuple(_, _) | PatKind::Struct(..) => {
// If this match is in a local (`let`) stmt
let (target_span, sugg) = if let Some(parent_let_node) = opt_parent_let(cx, ex) {
(
parent_let_node.span,
format!(
"let {} = {};\n{}let {} = {};",
snippet_with_applicability(cx, bind_names, "..", &mut applicability),
snippet_with_applicability(cx, matched_vars, "..", &mut applicability),
" ".repeat(indent_of(cx, expr.span).unwrap_or(0)),
snippet_with_applicability(cx, parent_let_node.pat.span, "..", &mut applicability),
snippet_body
),
)
} else {
(
expr.span,
format!(
"let {} = {};\n{}{}",
snippet_with_applicability(cx, bind_names, "..", &mut applicability),
snippet_with_applicability(cx, matched_vars, "..", &mut applicability),
" ".repeat(indent_of(cx, expr.span).unwrap_or(0)),
snippet_body
),
)
};
span_lint_and_sugg(
cx,
MATCH_SINGLE_BINDING,
expr.span,
target_span,
"this match could be written as a `let` statement",
"consider using `let` statement",
format!(
"let {} = {};\n{}{}",
snippet_with_applicability(cx, bind_names, "..", &mut applicability),
snippet_with_applicability(cx, matched_vars, "..", &mut applicability),
" ".repeat(indent_of(cx, expr.span).unwrap_or(0)),
snippet_body,
),
sugg,
applicability,
);
},
@ -945,6 +964,19 @@ fn check_match_single_binding(cx: &LateContext<'_, '_>, ex: &Expr<'_>, arms: &[A
}
}
/// Returns true if the `ex` match expression is in a local (`let`) statement
fn opt_parent_let<'a>(cx: &LateContext<'_, 'a>, ex: &Expr<'a>) -> Option<&'a Local<'a>> {
if_chain! {
let map = &cx.tcx.hir();
if let Some(Node::Expr(parent_arm_expr)) = map.find(map.get_parent_node(ex.hir_id));
if let Some(Node::Local(parent_let_expr)) = map.find(map.get_parent_node(parent_arm_expr.hir_id));
then {
return Some(parent_let_expr);
}
}
None
}
/// Gets all arms that are unbounded `PatRange`s.
fn all_ranges<'a, 'tcx>(
cx: &LateContext<'a, 'tcx>,

9
tests/ui/match_single_binding.fixed
View file

@ -1,13 +1,17 @@
// run-rustfix
#![warn(clippy::match_single_binding)]
#![allow(clippy::many_single_char_names, clippy::toplevel_ref_arg)]
#![allow(unused_variables, clippy::many_single_char_names, clippy::toplevel_ref_arg)]
struct Point {
x: i32,
y: i32,
}
fn coords() -> Point {
Point { x: 1, y: 2 }
}
fn main() {
let a = 1;
let b = 2;
@ -60,4 +64,7 @@ fn main() {
let mut x = 5;
let ref mut mr = x;
println!("Got a mutable reference to {}", mr);
// Lint
let Point { x, y } = coords();
let product = x * y;
}

10
tests/ui/match_single_binding.rs
View file

@ -1,13 +1,17 @@
// run-rustfix
#![warn(clippy::match_single_binding)]
#![allow(clippy::many_single_char_names, clippy::toplevel_ref_arg)]
#![allow(unused_variables, clippy::many_single_char_names, clippy::toplevel_ref_arg)]
struct Point {
x: i32,
y: i32,
}
fn coords() -> Point {
Point { x: 1, y: 2 }
}
fn main() {
let a = 1;
let b = 2;
@ -72,4 +76,8 @@ fn main() {
match x {
ref mut mr => println!("Got a mutable reference to {}", mr),
}
// Lint
let product = match coords() {
Point { x, y } => x * y,
};
}

34
tests/ui/match_single_binding.stderr
View file

@ -1,5 +1,5 @@
error: this match could be written as a `let` statement
--> $DIR/match_single_binding.rs:16:5
--> $DIR/match_single_binding.rs:20:5
|
LL | / match (a, b, c) {
LL | | (x, y, z) => {
@ -18,7 +18,7 @@ LL | }
|
error: this match could be written as a `let` statement
--> $DIR/match_single_binding.rs:22:5
--> $DIR/match_single_binding.rs:26:5
|
LL | / match (a, b, c) {
LL | | (x, y, z) => println!("{} {} {}", x, y, z),
@ -32,7 +32,7 @@ LL | println!("{} {} {}", x, y, z);
|
error: this match could be replaced by its body itself
--> $DIR/match_single_binding.rs:37:5
--> $DIR/match_single_binding.rs:41:5
|
LL | / match a {
LL | | _ => println!("whatever"),
@ -40,7 +40,7 @@ LL | | }
| |_____^ help: consider using the match body instead: `println!("whatever");`
error: this match could be replaced by its body itself
--> $DIR/match_single_binding.rs:41:5
--> $DIR/match_single_binding.rs:45:5
|
LL | / match a {
LL | | _ => {
@ -59,7 +59,7 @@ LL | }
|
error: this match could be replaced by its body itself
--> $DIR/match_single_binding.rs:48:5
--> $DIR/match_single_binding.rs:52:5
|
LL | / match a {
LL | | _ => {
@ -81,7 +81,7 @@ LL | }
|
error: this match could be written as a `let` statement
--> $DIR/match_single_binding.rs:58:5
--> $DIR/match_single_binding.rs:62:5
|
LL | / match p {
LL | | Point { x, y } => println!("Coords: ({}, {})", x, y),
@ -95,7 +95,7 @@ LL | println!("Coords: ({}, {})", x, y);
|
error: this match could be written as a `let` statement
--> $DIR/match_single_binding.rs:62:5
--> $DIR/match_single_binding.rs:66:5
|
LL | / match p {
LL | | Point { x: x1, y: y1 } => println!("Coords: ({}, {})", x1, y1),
@ -109,7 +109,7 @@ LL | println!("Coords: ({}, {})", x1, y1);
|
error: this match could be written as a `let` statement
--> $DIR/match_single_binding.rs:67:5
--> $DIR/match_single_binding.rs:71:5
|
LL | / match x {
LL | | ref r => println!("Got a reference to {}", r),
@ -123,7 +123,7 @@ LL | println!("Got a reference to {}", r);
|
error: this match could be written as a `let` statement
--> $DIR/match_single_binding.rs:72:5
--> $DIR/match_single_binding.rs:76:5
|
LL | / match x {
LL | | ref mut mr => println!("Got a mutable reference to {}", mr),
@ -136,5 +136,19 @@ LL | let ref mut mr = x;
LL | println!("Got a mutable reference to {}", mr);
|
error: aborting due to 9 previous errors
error: this match could be written as a `let` statement
--> $DIR/match_single_binding.rs:80:5
|
LL | / let product = match coords() {
LL | | Point { x, y } => x * y,
LL | | };
| |______^
|
help: consider using `let` statement
|
LL | let Point { x, y } = coords();
LL | let product = x * y;
|
error: aborting due to 10 previous errors