len_without_is_empty false positive #1740

tests/ui/len_zero.rs

@@ -125,6 +125,16 @@ impl HasWrongIsEmpty {
     }
 }
 
+pub trait Empty {
+    fn is_empty(&self) -> bool;
+}
+
+pub trait InheritingEmpty: Empty { //must not trigger LEN_WITHOUT_IS_EMPTY
+    fn len(&self) -> isize;
+}
+
+
+
 fn main() {
     let x = [1, 2];
     if x.len() == 0 {

tests/ui/len_zero.stderr

@@ -10,7 +10,7 @@ error: item `PubOne` has a public `len` method but no corresponding `is_empty` m
    |
    = note: `-D len-without-is-empty` implied by `-D warnings`
 
-error: trait `PubTraitsToo` has a `len` method but no `is_empty` method
+error: trait `PubTraitsToo` has a `len` method but no (possibly inherited) `is_empty` method
   --> $DIR/len_zero.rs:55:1
    |
 55 | / pub trait PubTraitsToo {
@@ -43,47 +43,47 @@ error: item `HasWrongIsEmpty` has a public `len` method but no corresponding `is
     | |_^
 
 error: length comparison to zero
-   --> $DIR/len_zero.rs:130:8
+   --> $DIR/len_zero.rs:140:8
     |
-130 |     if x.len() == 0 {
+140 |     if x.len() == 0 {
     |        ^^^^^^^^^^^^ help: using `is_empty` is more concise: `x.is_empty()`
     |
     = note: `-D len-zero` implied by `-D warnings`
 
 error: length comparison to zero
-   --> $DIR/len_zero.rs:134:8
+   --> $DIR/len_zero.rs:144:8
     |
-134 |     if "".len() == 0 {
+144 |     if "".len() == 0 {
     |        ^^^^^^^^^^^^^ help: using `is_empty` is more concise: `"".is_empty()`
 
 error: length comparison to zero
-   --> $DIR/len_zero.rs:148:8
+   --> $DIR/len_zero.rs:158:8
     |
-148 |     if has_is_empty.len() == 0 {
+158 |     if has_is_empty.len() == 0 {
     |        ^^^^^^^^^^^^^^^^^^^^^^^ help: using `is_empty` is more concise: `has_is_empty.is_empty()`
 
 error: length comparison to zero
-   --> $DIR/len_zero.rs:151:8
+   --> $DIR/len_zero.rs:161:8
     |
-151 |     if has_is_empty.len() != 0 {
+161 |     if has_is_empty.len() != 0 {
     |        ^^^^^^^^^^^^^^^^^^^^^^^ help: using `is_empty` is more concise: `!has_is_empty.is_empty()`
 
 error: length comparison to zero
-   --> $DIR/len_zero.rs:154:8
+   --> $DIR/len_zero.rs:164:8
     |
-154 |     if has_is_empty.len() > 0 {
+164 |     if has_is_empty.len() > 0 {
     |        ^^^^^^^^^^^^^^^^^^^^^^ help: using `is_empty` is more concise: `!has_is_empty.is_empty()`
 
 error: length comparison to zero
-   --> $DIR/len_zero.rs:160:8
+   --> $DIR/len_zero.rs:170:8
     |
-160 |     if with_is_empty.len() == 0 {
+170 |     if with_is_empty.len() == 0 {
     |        ^^^^^^^^^^^^^^^^^^^^^^^^ help: using `is_empty` is more concise: `with_is_empty.is_empty()`
 
 error: length comparison to zero
-   --> $DIR/len_zero.rs:172:8
+   --> $DIR/len_zero.rs:182:8
     |
-172 |     if b.len() != 0 {
+182 |     if b.len() != 0 {
     |        ^^^^^^^^^^^^ help: using `is_empty` is more concise: `!b.is_empty()`
 
 error: aborting due to 11 previous errors