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Auto merge of rust-lang#5350 - ThibsG:FixSingleBindingClosure, r=flip…
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Fix single binding closure

Fix the `match_single_binding` lint when triggered inside a closure.

Fixes: rust-lang#5347

changelog: Improve suggestion for [`match_single_binding`]
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bors committed Mar 23, 2020
2 parents 43bdee0 + badfbbb commit 1ff81c1
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Showing 4 changed files with 57 additions and 7 deletions.
26 changes: 20 additions & 6 deletions clippy_lints/src/matches.rs
Original file line number Diff line number Diff line change
Expand Up @@ -3,9 +3,10 @@ use crate::utils::paths;
use crate::utils::sugg::Sugg;
use crate::utils::usage::is_unused;
use crate::utils::{
expr_block, get_arg_name, in_macro, indent_of, is_allowed, is_expn_of, is_refutable, is_wild, match_qpath,
match_type, match_var, multispan_sugg, remove_blocks, snippet, snippet_block, snippet_with_applicability,
span_lint_and_help, span_lint_and_note, span_lint_and_sugg, span_lint_and_then, walk_ptrs_ty,
expr_block, get_arg_name, get_parent_expr, in_macro, indent_of, is_allowed, is_expn_of, is_refutable, is_wild,
match_qpath, match_type, match_var, multispan_sugg, remove_blocks, snippet, snippet_block,
snippet_with_applicability, span_lint_and_help, span_lint_and_note, span_lint_and_sugg, span_lint_and_then,
walk_ptrs_ty,
};
use if_chain::if_chain;
use rustc::lint::in_external_macro;
Expand Down Expand Up @@ -928,14 +929,27 @@ fn check_match_single_binding<'a>(cx: &LateContext<'_, 'a>, ex: &Expr<'a>, arms:
),
)
} else {
// If we are in closure, we need curly braces around suggestion
let mut indent = " ".repeat(indent_of(cx, ex.span).unwrap_or(0));
let (mut cbrace_start, mut cbrace_end) = ("".to_string(), "".to_string());
if let Some(parent_expr) = get_parent_expr(cx, expr) {
if let ExprKind::Closure(..) = parent_expr.kind {
cbrace_end = format!("\n{}}}", indent);
// Fix body indent due to the closure
indent = " ".repeat(indent_of(cx, bind_names).unwrap_or(0));
cbrace_start = format!("{{\n{}", indent);
}
};
(
expr.span,
format!(
"let {} = {};\n{}{}",
"{}let {} = {};\n{}{}{}",
cbrace_start,
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
indent,
snippet_body,
cbrace_end
),
)
};
Expand Down
10 changes: 10 additions & 0 deletions tests/ui/match_single_binding.fixed
Original file line number Diff line number Diff line change
Expand Up @@ -67,4 +67,14 @@ fn main() {
// Lint
let Point { x, y } = coords();
let product = x * y;
// Lint
let v = vec![Some(1), Some(2), Some(3), Some(4)];
#[allow(clippy::let_and_return)]
let _ = v
.iter()
.map(|i| {
let unwrapped = i.unwrap();
unwrapped
})
.collect::<Vec<u8>>();
}
9 changes: 9 additions & 0 deletions tests/ui/match_single_binding.rs
Original file line number Diff line number Diff line change
Expand Up @@ -80,4 +80,13 @@ fn main() {
let product = match coords() {
Point { x, y } => x * y,
};
// Lint
let v = vec![Some(1), Some(2), Some(3), Some(4)];
#[allow(clippy::let_and_return)]
let _ = v
.iter()
.map(|i| match i.unwrap() {
unwrapped => unwrapped,
})
.collect::<Vec<u8>>();
}
19 changes: 18 additions & 1 deletion tests/ui/match_single_binding.stderr
Original file line number Diff line number Diff line change
Expand Up @@ -150,5 +150,22 @@ LL | let Point { x, y } = coords();
LL | let product = x * y;
|

error: aborting due to 10 previous errors
error: this match could be written as a `let` statement
--> $DIR/match_single_binding.rs:88:18
|
LL | .map(|i| match i.unwrap() {
| __________________^
LL | | unwrapped => unwrapped,
LL | | })
| |_________^
|
help: consider using `let` statement
|
LL | .map(|i| {
LL | let unwrapped = i.unwrap();
LL | unwrapped
LL | })
|

error: aborting due to 11 previous errors

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