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Fix unit_arg false positive

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Ignore arguments with the question mark operator.

Closes #2945
This commit is contained in:
Michael Wright 2019-01-29 07:22:08 +02:00
parent 410d5ba6c3
commit df04238d3a
3 changed files with 53 additions and 24 deletions
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55
clippy_lints/src/types.rs
View file

@ -609,36 +609,43 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitArg {
if in_macro(expr.span) {
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;
}
if_chain! {
let map = &cx.tcx.hir();
let opt_parent_node = map.find(map.get_parent_node(expr.id));
if let Some(hir::Node::Expr(parent_expr)) = opt_parent_node;
if is_questionmark_desugar_marked_call(parent_expr);
then {
return;
}
}
match expr.node {
ExprKind::Call(_, ref args) | ExprKind::MethodCall(_, _, ref args) => {
for arg in args {
if is_unit(cx.tables.expr_ty(arg)) && !is_unit_literal(arg) {
let map = &cx.tcx.hir();
// 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) {
if_chain! {
let opt_parent_node = map.find(map.get_parent_node(expr.id));
if let Some(hir::Node::Expr(parent_expr)) = opt_parent_node;
if is_questionmark_desugar_marked_call(parent_expr);
then {}
else {
// `expr` and `parent_expr` where _both_ not from
// desugaring `?`, so lint
span_lint_and_sugg(
cx,
UNIT_ARG,
arg.span,
"passing a unit value to a function",
"if you intended to pass a unit value, use a unit literal instead",
"()".to_string(),
Applicability::MachineApplicable,
);
}
if let ExprKind::Match(.., match_source) = &arg.node {
if *match_source == MatchSource::TryDesugar {
continue;
}
}
span_lint_and_sugg(
cx,
UNIT_ARG,
arg.span,
"passing a unit value to a function",
"if you intended to pass a unit value, use a unit literal instead",
"()".to_string(),
Applicability::MachineApplicable,
);
}
}
},

11
tests/ui/unit_arg.fixed
View file

@ -47,6 +47,17 @@ fn question_mark() -> Result<(), ()> {
Ok(())
}
#[allow(dead_code)]
mod issue_2945 {
fn unit_fn() -> Result<(), i32> {
Ok(())
}
fn fallible() -> Result<(), i32> {
Ok(unit_fn()?)
}
}
fn main() {
bad();
ok();

11
tests/ui/unit_arg.rs
View file

@ -54,6 +54,17 @@ fn question_mark() -> Result<(), ()> {
Ok(())
}
#[allow(dead_code)]
mod issue_2945 {
fn unit_fn() -> Result<(), i32> {
Ok(())
}
fn fallible() -> Result<(), i32> {
Ok(unit_fn()?)
}
}
fn main() {
bad();
ok();