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make needless_return work with void functions

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This commit is contained in:
Daniele D'Orazio 2019-06-19 14:56:02 +02:00
parent 5a11ed7b92
commit 6396a7a425
3 changed files with 108 additions and 29 deletions
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51
clippy_lints/src/returns.rs
View file

@ -83,6 +83,12 @@ declare_clippy_lint! {
"needless unit expression"
}
#[derive(PartialEq, Eq, Copy, Clone)]
enum RetReplacement {
Empty,
Unit
}
declare_lint_pass!(Return => [NEEDLESS_RETURN, LET_AND_RETURN, UNUSED_UNIT]);
impl Return {
@ -91,7 +97,7 @@ impl Return {
if let Some(stmt) = block.stmts.last() {
match stmt.node {
ast::StmtKind::Expr(ref expr) | ast::StmtKind::Semi(ref expr) => {
self.check_final_expr(cx, expr, Some(stmt.span));
self.check_final_expr(cx, expr, Some(stmt.span), RetReplacement::Empty);
},
_ => (),
}
@ -99,13 +105,13 @@ impl Return {
}
// Check a the final expression in a block if it's a return.
fn check_final_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr, span: Option<Span>) {
fn check_final_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr, span: Option<Span>, replacement: RetReplacement) {
match expr.node {
// simple return is always "bad"
ast::ExprKind::Ret(Some(ref inner)) => {
ast::ExprKind::Ret(ref inner) => {
// allow `#[cfg(a)] return a; #[cfg(b)] return b;`
if !expr.attrs.iter().any(attr_is_cfg) {
self.emit_return_lint(cx, span.expect("`else return` is not possible"), inner.span);
self.emit_return_lint(cx, span.expect("`else return` is not possible"), inner.as_ref().map(|i| i.span), replacement);
}
},
// a whole block? check it!
@ -117,22 +123,25 @@ impl Return {
// (except for unit type functions) so we don't match it
ast::ExprKind::If(_, ref ifblock, Some(ref elsexpr)) => {
self.check_block_return(cx, ifblock);
self.check_final_expr(cx, elsexpr, None);
self.check_final_expr(cx, elsexpr, None, RetReplacement::Empty);
},
// a match expr, check all arms
ast::ExprKind::Match(_, ref arms) => {
for arm in arms {
self.check_final_expr(cx, &arm.body, Some(arm.body.span));
self.check_final_expr(cx, &arm.body, Some(arm.body.span), RetReplacement::Unit);
}
},
_ => (),
}
}
fn emit_return_lint(&mut self, cx: &EarlyContext<'_>, ret_span: Span, inner_span: Span) {
fn emit_return_lint(&mut self, cx: &EarlyContext<'_>, ret_span: Span, inner_span: Option<Span>, replacement: RetReplacement) {
match inner_span {
Some(inner_span) => {
if in_external_macro(cx.sess(), inner_span) || in_macro_or_desugar(inner_span) {
return;
}
span_lint_and_then(cx, NEEDLESS_RETURN, ret_span, "unneeded return statement", |db| {
if let Some(snippet) = snippet_opt(cx, inner_span) {
db.span_suggestion(
@ -142,8 +151,34 @@ impl Return {
Applicability::MachineApplicable,
);
}
})
},
None => {
match replacement {
RetReplacement::Empty => {
span_lint_and_then(cx, NEEDLESS_RETURN, ret_span, "unneeded return statement", |db| {
db.span_suggestion(
ret_span,
"remove `return`",
String::new(),
Applicability::MachineApplicable,
);
});
}
RetReplacement::Unit => {
span_lint_and_then(cx, NEEDLESS_RETURN, ret_span, "unneeded return statement", |db| {
db.span_suggestion(
ret_span,
"replace `return` with the unit type `()`",
"()".to_string(),
Applicability::MachineApplicable,
);
});
}
}
}
}
}
// Check for "let x = EXPR; x"
fn check_let_return(&mut self, cx: &EarlyContext<'_>, block: &ast::Block) {
@ -195,7 +230,7 @@ impl EarlyLintPass for Return {
fn check_fn(&mut self, cx: &EarlyContext<'_>, kind: FnKind<'_>, decl: &ast::FnDecl, span: Span, _: ast::NodeId) {
match kind {
FnKind::ItemFn(.., block) | FnKind::Method(.., block) => self.check_block_return(cx, block),
FnKind::Closure(body) => self.check_final_expr(cx, body, Some(body.span)),
FnKind::Closure(body) => self.check_final_expr(cx, body, Some(body.span), RetReplacement::Empty),
}
if_chain! {
if let ast::FunctionRetTy::Ty(ref ty) = decl.output;

20
tests/ui/needless_return.rs
View file

@ -1,5 +1,9 @@
#![warn(clippy::needless_return)]
macro_rules! the_answer {
() => (42)
}
fn test_end_of_fn() -> bool {
if true {
// no error!
@ -36,6 +40,22 @@ fn test_closure() {
let _ = || return true;
}
fn test_macro_call() -> i32 {
return the_answer!();
}
fn test_void_fun() {
return;
}
fn test_void_if_fun(b: bool) {
if b {
return;
} else {
return;
}
}
fn main() {
let _ = test_end_of_fn();
let _ = test_no_semicolon();

42
tests/ui/needless_return.stderr
View file

@ -1,5 +1,5 @@
error: unneeded return statement
--> $DIR/needless_return.rs:8:5
--> $DIR/needless_return.rs:12:5
|
LL | return true;
| ^^^^^^^^^^^^ help: remove `return` as shown: `true`
@ -7,46 +7,70 @@ LL | return true;
= note: `-D clippy::needless-return` implied by `-D warnings`
error: unneeded return statement
--> $DIR/needless_return.rs:12:5
--> $DIR/needless_return.rs:16:5
|
LL | return true;
| ^^^^^^^^^^^^ help: remove `return` as shown: `true`
error: unneeded return statement
--> $DIR/needless_return.rs:17:9
--> $DIR/needless_return.rs:21:9
|
LL | return true;
| ^^^^^^^^^^^^ help: remove `return` as shown: `true`
error: unneeded return statement
--> $DIR/needless_return.rs:19:9
--> $DIR/needless_return.rs:23:9
|
LL | return false;
| ^^^^^^^^^^^^^ help: remove `return` as shown: `false`
error: unneeded return statement
--> $DIR/needless_return.rs:25:17
--> $DIR/needless_return.rs:29:17
|
LL | true => return false,
| ^^^^^^^^^^^^ help: remove `return` as shown: `false`
error: unneeded return statement
--> $DIR/needless_return.rs:27:13
--> $DIR/needless_return.rs:31:13
|
LL | return true;
| ^^^^^^^^^^^^ help: remove `return` as shown: `true`
error: unneeded return statement
--> $DIR/needless_return.rs:34:9
--> $DIR/needless_return.rs:38:9
|
LL | return true;
| ^^^^^^^^^^^^ help: remove `return` as shown: `true`
error: unneeded return statement
--> $DIR/needless_return.rs:36:16
--> $DIR/needless_return.rs:40:16
|
LL | let _ = || return true;
| ^^^^^^^^^^^ help: remove `return` as shown: `true`
error: aborting due to 8 previous errors
error: unneeded return statement
--> $DIR/needless_return.rs:44:5
|
LL | return the_answer!();
| ^^^^^^^^^^^^^^^^^^^^^
error: unneeded return statement
--> $DIR/needless_return.rs:48:5
|
LL | return;
| ^^^^^^^ help: remove `return`
error: unneeded return statement
--> $DIR/needless_return.rs:53:9
|
LL | return;
| ^^^^^^^ help: remove `return`
error: unneeded return statement
--> $DIR/needless_return.rs:55:9
|
LL | return;
| ^^^^^^^ help: remove `return`
error: aborting due to 12 previous errors