diff options
| -rw-r--r-- | compiler/rustc_lint/src/noop_method_call.rs | 9 | ||||
| -rw-r--r-- | src/test/ui/issues/issue-11820.rs | 8 | ||||
| -rw-r--r-- | src/test/ui/lint/noop-method-call.rs | 9 | ||||
| -rw-r--r-- | src/test/ui/lint/noop-method-call.stderr | 19 |
4 files changed, 30 insertions, 15 deletions
diff --git a/compiler/rustc_lint/src/noop_method_call.rs b/compiler/rustc_lint/src/noop_method_call.rs index b9b5009d9dd..e91dd37d8aa 100644 --- a/compiler/rustc_lint/src/noop_method_call.rs +++ b/compiler/rustc_lint/src/noop_method_call.rs @@ -39,7 +39,7 @@ declare_lint_pass!(NoopMethodCall => [NOOP_METHOD_CALL]); impl<'tcx> LateLintPass<'tcx> for NoopMethodCall { fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) { // We only care about method calls - if let ExprKind::MethodCall(..) = expr.kind { + if let ExprKind::MethodCall(call, ..) = expr.kind { // Get the `DefId` only when dealing with an `AssocFn` if let Some((DefKind::AssocFn, did)) = cx.typeck_results().type_dependent_def(expr.hir_id) @@ -55,7 +55,7 @@ impl<'tcx> LateLintPass<'tcx> for NoopMethodCall { } let substs = cx.typeck_results().node_substs(expr.hir_id); - // We can't resolve on types that recursively require monomorphization, + // We can't resolve on types that require monomorphization, // so check that we don't need to perfom substitution if !substs.needs_subst() { let param_env = cx.tcx.param_env(trait_id); @@ -73,9 +73,12 @@ impl<'tcx> LateLintPass<'tcx> for NoopMethodCall { let expr_span = expr.span; cx.struct_span_lint(NOOP_METHOD_CALL, expr_span, |lint| { - let message = "call to method that does nothing"; + let method = &call.ident.name; + let message = format!("call to `.{}()` on a reference in this situation does nothing", &method); lint.build(&message) .span_label(expr_span, "unnecessary method call") + .note("the type the method is being called on and the return type are functionally equivalent.") + .note("therefore, the method call doesn't actually do anything and can be removed.") .emit() }); } diff --git a/src/test/ui/issues/issue-11820.rs b/src/test/ui/issues/issue-11820.rs index 8a26624a05d..dc6349b10ee 100644 --- a/src/test/ui/issues/issue-11820.rs +++ b/src/test/ui/issues/issue-11820.rs @@ -6,9 +6,9 @@ struct NoClone; fn main() { - let rnc = &NoClone; - let rsnc = &Some(NoClone); + let rnc = &NoClone; + let rsnc = &Some(NoClone); - let _: &NoClone = rnc.clone(); - let _: &Option<NoClone> = rsnc.clone(); + let _: &NoClone = rnc.clone(); + let _: &Option<NoClone> = rsnc.clone(); } diff --git a/src/test/ui/lint/noop-method-call.rs b/src/test/ui/lint/noop-method-call.rs index 9f0ab3960f8..b8aa55e1e1d 100644 --- a/src/test/ui/lint/noop-method-call.rs +++ b/src/test/ui/lint/noop-method-call.rs @@ -22,21 +22,21 @@ impl<T> Deref for DerefExample<T> { fn main() { let foo = &Foo(1u32); let foo_clone: &Foo<u32> = foo.clone(); - //~^ WARNING call to method that does nothing [noop_method_call] + //~^ WARNING call to `.clone()` on a reference in this situation does nothing [noop_method_call] let bar = &Bar(1u32); let bar_clone: Bar<u32> = bar.clone(); let deref = &&DerefExample(12u32); let derefed: &DerefExample<u32> = deref.deref(); - //~^ WARNING call to method that does nothing [noop_method_call] + //~^ WARNING call to `.deref()` on a reference in this situation does nothing [noop_method_call] let deref = &DerefExample(12u32); let derefed: &u32 = deref.deref(); let a = &&Foo(1u32); let borrowed: &Foo<u32> = a.borrow(); - //~^ WARNING call to method that does nothing [noop_method_call] + //~^ WARNING call to `.borrow()` on a reference in this situation does nothing [noop_method_call] } fn generic<T>(foo: &Foo<T>) { @@ -44,5 +44,6 @@ fn generic<T>(foo: &Foo<T>) { } fn non_generic(foo: &Foo<u32>) { - foo.clone(); //~ WARNING call to method that does nothing [noop_method_call] + foo.clone(); + //~^ WARNING call to `.clone()` on a reference in this situation does nothing [noop_method_call] } diff --git a/src/test/ui/lint/noop-method-call.stderr b/src/test/ui/lint/noop-method-call.stderr index 32acf163233..f9cc9735d54 100644 --- a/src/test/ui/lint/noop-method-call.stderr +++ b/src/test/ui/lint/noop-method-call.stderr @@ -1,28 +1,39 @@ -warning: call to method that does nothing +warning: call to `.clone()` on a reference in this situation does nothing --> $DIR/noop-method-call.rs:24:32 | LL | let foo_clone: &Foo<u32> = foo.clone(); | ^^^^^^^^^^^ unnecessary method call | = note: `#[warn(noop_method_call)]` on by default + = note: the type the method is being called on and the return type are functionally equivalent. + = note: therefore, the method call doesn't actually do anything and can be removed. -warning: call to method that does nothing +warning: call to `.deref()` on a reference in this situation does nothing --> $DIR/noop-method-call.rs:31:39 | LL | let derefed: &DerefExample<u32> = deref.deref(); | ^^^^^^^^^^^^^ unnecessary method call + | + = note: the type the method is being called on and the return type are functionally equivalent. + = note: therefore, the method call doesn't actually do anything and can be removed. -warning: call to method that does nothing +warning: call to `.borrow()` on a reference in this situation does nothing --> $DIR/noop-method-call.rs:38:31 | LL | let borrowed: &Foo<u32> = a.borrow(); | ^^^^^^^^^^ unnecessary method call + | + = note: the type the method is being called on and the return type are functionally equivalent. + = note: therefore, the method call doesn't actually do anything and can be removed. -warning: call to method that does nothing +warning: call to `.clone()` on a reference in this situation does nothing --> $DIR/noop-method-call.rs:47:5 | LL | foo.clone(); | ^^^^^^^^^^^ unnecessary method call + | + = note: the type the method is being called on and the return type are functionally equivalent. + = note: therefore, the method call doesn't actually do anything and can be removed. warning: 4 warnings emitted |