Lint path statements to use drop for drop types

This commit is contained in:
Lukas Wirth 2020-08-02 16:30:09 +02:00
parent dfe1e3b641
commit 35d6a2ef2b
3 changed files with 44 additions and 5 deletions

View File

@ -275,10 +275,26 @@ fn check_must_use_def(
impl<'tcx> LateLintPass<'tcx> for PathStatements {
fn check_stmt(&mut self, cx: &LateContext<'_>, s: &hir::Stmt<'_>) {
if let hir::StmtKind::Semi(ref expr) = s.kind {
if let hir::StmtKind::Semi(expr) = s.kind {
if let hir::ExprKind::Path(_) = expr.kind {
cx.struct_span_lint(PATH_STATEMENTS, s.span, |lint| {
lint.build("path statement with no effect").emit()
let ty = cx.typeck_results().expr_ty(expr);
if ty.needs_drop(cx.tcx, cx.param_env) {
let mut lint = lint.build("path statement drops value");
if let Ok(snippet) = cx.sess().source_map().span_to_snippet(expr.span) {
lint.span_suggestion(
s.span,
"use `drop` to clarify the intent",
format!("drop({});", snippet),
Applicability::MachineApplicable,
);
} else {
lint.span_help(s.span, "use `drop` to clarify the intent");
}
lint.emit()
} else {
lint.build("path statement with no effect").emit()
}
});
}
}

View File

@ -1,6 +1,17 @@
// compile-flags: -D path-statements
fn main() {
struct Droppy;
impl Drop for Droppy {
fn drop(&mut self) {}
}
fn main() {
let x = 10;
x; //~ ERROR path statement with no effect
let y = Droppy;
y; //~ ERROR path statement drops value
let z = (Droppy,);
z; //~ ERROR path statement drops value
}

View File

@ -1,10 +1,22 @@
error: path statement with no effect
--> $DIR/warn-path-statement.rs:5:5
--> $DIR/warn-path-statement.rs:10:5
|
LL | x;
| ^^
|
= note: requested on the command line with `-D path-statements`
error: aborting due to previous error
error: path statement drops value
--> $DIR/warn-path-statement.rs:13:5
|
LL | y;
| ^^ help: use `drop` to clarify the intent: `drop(y);`
error: path statement drops value
--> $DIR/warn-path-statement.rs:16:5
|
LL | z;
| ^^ help: use `drop` to clarify the intent: `drop(z);`
error: aborting due to 3 previous errors