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|
use clippy_utils::diagnostics::span_lint_and_then;
use clippy_utils::source::{indent_of, reindent_multiline, snippet_opt};
use if_chain::if_chain;
use rustc_errors::Applicability;
use rustc_hir::{self as hir, Block, Expr, ExprKind, MatchSource, Node, StmtKind};
use rustc_lint::LateContext;
use super::{utils, UNIT_ARG};
pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>) {
if expr.span.from_expansion() {
return;
}
// apparently stuff in the desugaring of `?` can trigger this
// so check for that here
// only the calls to `Try::from_error` is marked as desugared,
// so we need to check both the current Expr and its parent.
if is_questionmark_desugar_marked_call(expr) {
return;
}
let map = &cx.tcx.hir();
let opt_parent_node = map.find(map.get_parent_node(expr.hir_id));
if_chain! {
if let Some(hir::Node::Expr(parent_expr)) = opt_parent_node;
if is_questionmark_desugar_marked_call(parent_expr);
then {
return;
}
}
match expr.kind {
ExprKind::Call(_, args) | ExprKind::MethodCall(_, args, _) => {
let args_to_recover = args
.iter()
.filter(|arg| {
if cx.typeck_results().expr_ty(arg).is_unit() && !utils::is_unit_literal(arg) {
!matches!(
&arg.kind,
ExprKind::Match(.., MatchSource::TryDesugar) | ExprKind::Path(..)
)
} else {
false
}
})
.collect::<Vec<_>>();
if !args_to_recover.is_empty() {
lint_unit_args(cx, expr, &args_to_recover);
}
},
_ => (),
}
}
fn is_questionmark_desugar_marked_call(expr: &Expr<'_>) -> bool {
use rustc_span::hygiene::DesugaringKind;
if let ExprKind::Call(callee, _) = expr.kind {
callee.span.is_desugaring(DesugaringKind::QuestionMark)
} else {
false
}
}
fn lint_unit_args(cx: &LateContext<'_>, expr: &Expr<'_>, args_to_recover: &[&Expr<'_>]) {
let mut applicability = Applicability::MachineApplicable;
let (singular, plural) = if args_to_recover.len() > 1 {
("", "s")
} else {
("a ", "")
};
span_lint_and_then(
cx,
UNIT_ARG,
expr.span,
&format!("passing {}unit value{} to a function", singular, plural),
|db| {
let mut or = "";
args_to_recover
.iter()
.filter_map(|arg| {
if_chain! {
if let ExprKind::Block(block, _) = arg.kind;
if block.expr.is_none();
if let Some(last_stmt) = block.stmts.iter().last();
if let StmtKind::Semi(last_expr) = last_stmt.kind;
if let Some(snip) = snippet_opt(cx, last_expr.span);
then {
Some((
last_stmt.span,
snip,
))
}
else {
None
}
}
})
.for_each(|(span, sugg)| {
db.span_suggestion(
span,
"remove the semicolon from the last statement in the block",
sugg,
Applicability::MaybeIncorrect,
);
or = "or ";
applicability = Applicability::MaybeIncorrect;
});
let arg_snippets: Vec<String> = args_to_recover
.iter()
.filter_map(|arg| snippet_opt(cx, arg.span))
.collect();
let arg_snippets_without_empty_blocks: Vec<String> = args_to_recover
.iter()
.filter(|arg| !is_empty_block(arg))
.filter_map(|arg| snippet_opt(cx, arg.span))
.collect();
if let Some(call_snippet) = snippet_opt(cx, expr.span) {
let sugg = fmt_stmts_and_call(
cx,
expr,
&call_snippet,
&arg_snippets,
&arg_snippets_without_empty_blocks,
);
if arg_snippets_without_empty_blocks.is_empty() {
db.multipart_suggestion(
&format!("use {}unit literal{} instead", singular, plural),
args_to_recover
.iter()
.map(|arg| (arg.span, "()".to_string()))
.collect::<Vec<_>>(),
applicability,
);
} else {
let plural = arg_snippets_without_empty_blocks.len() > 1;
let empty_or_s = if plural { "s" } else { "" };
let it_or_them = if plural { "them" } else { "it" };
db.span_suggestion(
expr.span,
&format!(
"{}move the expression{} in front of the call and replace {} with the unit literal `()`",
or, empty_or_s, it_or_them
),
sugg,
applicability,
);
}
}
},
);
}
fn is_empty_block(expr: &Expr<'_>) -> bool {
matches!(
expr.kind,
ExprKind::Block(
Block {
stmts: &[],
expr: None,
..
},
_,
)
)
}
fn fmt_stmts_and_call(
cx: &LateContext<'_>,
call_expr: &Expr<'_>,
call_snippet: &str,
args_snippets: &[impl AsRef<str>],
non_empty_block_args_snippets: &[impl AsRef<str>],
) -> String {
let call_expr_indent = indent_of(cx, call_expr.span).unwrap_or(0);
let call_snippet_with_replacements = args_snippets
.iter()
.fold(call_snippet.to_owned(), |acc, arg| acc.replacen(arg.as_ref(), "()", 1));
let mut stmts_and_call = non_empty_block_args_snippets
.iter()
.map(|it| it.as_ref().to_owned())
.collect::<Vec<_>>();
stmts_and_call.push(call_snippet_with_replacements);
stmts_and_call = stmts_and_call
.into_iter()
.map(|v| reindent_multiline(v.into(), true, Some(call_expr_indent)).into_owned())
.collect();
let mut stmts_and_call_snippet = stmts_and_call.join(&format!("{}{}", ";\n", " ".repeat(call_expr_indent)));
// expr is not in a block statement or result expression position, wrap in a block
let parent_node = cx.tcx.hir().find(cx.tcx.hir().get_parent_node(call_expr.hir_id));
if !matches!(parent_node, Some(Node::Block(_))) && !matches!(parent_node, Some(Node::Stmt(_))) {
let block_indent = call_expr_indent + 4;
stmts_and_call_snippet =
reindent_multiline(stmts_and_call_snippet.into(), true, Some(block_indent)).into_owned();
stmts_and_call_snippet = format!(
"{{\n{}{}\n{}}}",
" ".repeat(block_indent),
&stmts_and_call_snippet,
" ".repeat(call_expr_indent)
);
}
stmts_and_call_snippet
}
|
