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Split out match_single_binding

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Jason Newcomb 2022-02-06 16:38:34 -05:00
parent bccf06f601
commit 1da26c8a70
2 changed files with 171 additions and 163 deletions
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166
clippy_lints/src/matches/match_single_binding.rs Normal file
View file

@ -0,0 +1,166 @@
use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::source::{indent_of, snippet_block, snippet_opt, snippet_with_applicability};
use clippy_utils::sugg::Sugg;
use clippy_utils::{get_parent_expr, is_refutable, peel_blocks};
use rustc_errors::Applicability;
use rustc_hir::{Arm, Expr, ExprKind, Local, Node, PatKind};
use rustc_lint::LateContext;
use super::MATCH_SINGLE_BINDING;
#[allow(clippy::too_many_lines)]
pub(crate) fn check<'a>(cx: &LateContext<'a>, ex: &Expr<'a>, arms: &[Arm<'_>], expr: &Expr<'_>) {
if expr.span.from_expansion() || arms.len() != 1 || is_refutable(cx, arms[0].pat) {
return;
}
// HACK:
// This is a hack to deal with arms that are excluded by macros like `#[cfg]`. It is only used here
// to prevent false positives as there is currently no better way to detect if code was excluded by
// a macro. See PR #6435
if_chain! {
if let Some(match_snippet) = snippet_opt(cx, expr.span);
if let Some(arm_snippet) = snippet_opt(cx, arms[0].span);
if let Some(ex_snippet) = snippet_opt(cx, ex.span);
let rest_snippet = match_snippet.replace(&arm_snippet, "").replace(&ex_snippet, "");
if rest_snippet.contains("=>");
then {
// The code it self contains another thick arrow "=>"
// -> Either another arm or a comment
return;
}
}
let matched_vars = ex.span;
let bind_names = arms[0].pat.span;
let match_body = peel_blocks(arms[0].body);
let mut snippet_body = if match_body.span.from_expansion() {
Sugg::hir_with_macro_callsite(cx, match_body, "..").to_string()
} else {
snippet_block(cx, match_body.span, "..", Some(expr.span)).to_string()
};
// Do we need to add ';' to suggestion ?
match match_body.kind {
ExprKind::Block(block, _) => {
// macro + expr_ty(body) == ()
if block.span.from_expansion() && cx.typeck_results().expr_ty(match_body).is_unit() {
snippet_body.push(';');
}
},
_ => {
// expr_ty(body) == ()
if cx.typeck_results().expr_ty(match_body).is_unit() {
snippet_body.push(';');
}
},
}
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 {
// 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);
}
}
// If the parent is already an arm, and the body is another match statement,
// we need curly braces around suggestion
let parent_node_id = cx.tcx.hir().get_parent_node(expr.hir_id);
if let Node::Arm(arm) = &cx.tcx.hir().get(parent_node_id) {
if let ExprKind::Match(..) = arm.body.kind {
cbrace_end = format!("\n{}}}", indent);
// Fix body indent due to the match
indent = " ".repeat(indent_of(cx, bind_names).unwrap_or(0));
cbrace_start = format!("{{\n{}", indent);
}
}
(
expr.span,
format!(
"{}let {} = {};\n{}{}{}",
cbrace_start,
snippet_with_applicability(cx, bind_names, "..", &mut applicability),
snippet_with_applicability(cx, matched_vars, "..", &mut applicability),
indent,
snippet_body,
cbrace_end
),
)
};
span_lint_and_sugg(
cx,
MATCH_SINGLE_BINDING,
target_span,
"this match could be written as a `let` statement",
"consider using `let` statement",
sugg,
applicability,
);
},
PatKind::Wild => {
if ex.can_have_side_effects() {
let indent = " ".repeat(indent_of(cx, expr.span).unwrap_or(0));
let sugg = format!(
"{};\n{}{}",
snippet_with_applicability(cx, ex.span, "..", &mut applicability),
indent,
snippet_body
);
span_lint_and_sugg(
cx,
MATCH_SINGLE_BINDING,
expr.span,
"this match could be replaced by its scrutinee and body",
"consider using the scrutinee and body instead",
sugg,
applicability,
);
} else {
span_lint_and_sugg(
cx,
MATCH_SINGLE_BINDING,
expr.span,
"this match could be replaced by its body itself",
"consider using the match body instead",
snippet_body,
Applicability::MachineApplicable,
);
}
},
_ => (),
}
}
/// 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>> {
let map = &cx.tcx.hir();
if_chain! {
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
}

168
clippy_lints/src/matches/mod.rs
View file

@ -1,13 +1,11 @@
use clippy_utils::diagnostics::{multispan_sugg, span_lint_and_help, span_lint_and_sugg, span_lint_and_then};
use clippy_utils::source::{indent_of, snippet, snippet_block, snippet_opt, snippet_with_applicability};
use clippy_utils::source::{snippet, snippet_with_applicability};
use clippy_utils::sugg::Sugg;
use clippy_utils::{
get_parent_expr, is_refutable, is_wild, meets_msrv, msrvs, path_to_local_id, peel_blocks, strip_pat_refs,
};
use clippy_utils::{is_wild, meets_msrv, msrvs, path_to_local_id, peel_blocks, strip_pat_refs};
use core::iter::once;
use if_chain::if_chain;
use rustc_errors::Applicability;
use rustc_hir::{Arm, BorrowKind, Expr, ExprKind, Local, MatchSource, Mutability, Node, Pat, PatKind, QPath};
use rustc_hir::{Arm, BorrowKind, Expr, ExprKind, Local, MatchSource, Mutability, Pat, PatKind, QPath};
use rustc_lint::{LateContext, LateLintPass};
use rustc_middle::ty;
use rustc_semver::RustcVersion;
@ -17,6 +15,7 @@ mod match_as_ref;
mod match_bool;
mod match_like_matches;
mod match_same_arms;
mod match_single_binding;
mod match_wild_enum;
mod match_wild_err_arm;
mod overlapping_arms;
@ -630,7 +629,7 @@ impl<'tcx> LateLintPass<'tcx> for Matches {
if self.infallible_destructuring_match_linted {
self.infallible_destructuring_match_linted = false;
} else {
check_match_single_binding(cx, ex, arms, expr);
match_single_binding::check(cx, ex, arms, expr);
}
}
if let ExprKind::Match(ex, arms, _) = expr.kind {
@ -753,163 +752,6 @@ fn check_wild_in_or_pats(cx: &LateContext<'_>, arms: &[Arm<'_>]) {
}
}
#[allow(clippy::too_many_lines)]
fn check_match_single_binding<'a>(cx: &LateContext<'a>, ex: &Expr<'a>, arms: &[Arm<'_>], expr: &Expr<'_>) {
if expr.span.from_expansion() || arms.len() != 1 || is_refutable(cx, arms[0].pat) {
return;
}
// HACK:
// This is a hack to deal with arms that are excluded by macros like `#[cfg]`. It is only used here
// to prevent false positives as there is currently no better way to detect if code was excluded by
// a macro. See PR #6435
if_chain! {
if let Some(match_snippet) = snippet_opt(cx, expr.span);
if let Some(arm_snippet) = snippet_opt(cx, arms[0].span);
if let Some(ex_snippet) = snippet_opt(cx, ex.span);
let rest_snippet = match_snippet.replace(&arm_snippet, "").replace(&ex_snippet, "");
if rest_snippet.contains("=>");
then {
// The code it self contains another thick arrow "=>"
// -> Either another arm or a comment
return;
}
}
let matched_vars = ex.span;
let bind_names = arms[0].pat.span;
let match_body = peel_blocks(arms[0].body);
let mut snippet_body = if match_body.span.from_expansion() {
Sugg::hir_with_macro_callsite(cx, match_body, "..").to_string()
} else {
snippet_block(cx, match_body.span, "..", Some(expr.span)).to_string()
};
// Do we need to add ';' to suggestion ?
match match_body.kind {
ExprKind::Block(block, _) => {
// macro + expr_ty(body) == ()
if block.span.from_expansion() && cx.typeck_results().expr_ty(match_body).is_unit() {
snippet_body.push(';');
}
},
_ => {
// expr_ty(body) == ()
if cx.typeck_results().expr_ty(match_body).is_unit() {
snippet_body.push(';');
}
},
}
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 {
// 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);
}
}
// If the parent is already an arm, and the body is another match statement,
// we need curly braces around suggestion
let parent_node_id = cx.tcx.hir().get_parent_node(expr.hir_id);
if let Node::Arm(arm) = &cx.tcx.hir().get(parent_node_id) {
if let ExprKind::Match(..) = arm.body.kind {
cbrace_end = format!("\n{}}}", indent);
// Fix body indent due to the match
indent = " ".repeat(indent_of(cx, bind_names).unwrap_or(0));
cbrace_start = format!("{{\n{}", indent);
}
}
(
expr.span,
format!(
"{}let {} = {};\n{}{}{}",
cbrace_start,
snippet_with_applicability(cx, bind_names, "..", &mut applicability),
snippet_with_applicability(cx, matched_vars, "..", &mut applicability),
indent,
snippet_body,
cbrace_end
),
)
};
span_lint_and_sugg(
cx,
MATCH_SINGLE_BINDING,
target_span,
"this match could be written as a `let` statement",
"consider using `let` statement",
sugg,
applicability,
);
},
PatKind::Wild => {
if ex.can_have_side_effects() {
let indent = " ".repeat(indent_of(cx, expr.span).unwrap_or(0));
let sugg = format!(
"{};\n{}{}",
snippet_with_applicability(cx, ex.span, "..", &mut applicability),
indent,
snippet_body
);
span_lint_and_sugg(
cx,
MATCH_SINGLE_BINDING,
expr.span,
"this match could be replaced by its scrutinee and body",
"consider using the scrutinee and body instead",
sugg,
applicability,
);
} else {
span_lint_and_sugg(
cx,
MATCH_SINGLE_BINDING,
expr.span,
"this match could be replaced by its body itself",
"consider using the match body instead",
snippet_body,
Applicability::MachineApplicable,
);
}
},
_ => (),
}
}
/// 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>> {
let map = &cx.tcx.hir();
if_chain! {
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
}
fn has_multiple_ref_pats<'a, 'b, I>(pats: I) -> bool
where
'b: 'a,