Add run-rustfix to unnecessary_fold

tests/ui/unnecessary_fold.fixed

@@ -0,0 +1,44 @@
+// run-rustfix
+
+#![allow(dead_code)]
+
+/// Calls which should trigger the `UNNECESSARY_FOLD` lint
+fn unnecessary_fold() {
+    // Can be replaced by .any
+    let _ = (0..3).any(|x| x > 2);
+    // Can be replaced by .all
+    let _ = (0..3).all(|x| x > 2);
+    // Can be replaced by .sum
+    let _: i32 = (0..3).sum();
+    // Can be replaced by .product
+    let _: i32 = (0..3).product();
+}
+
+/// Should trigger the `UNNECESSARY_FOLD` lint, with an error span including exactly `.fold(...)`
+fn unnecessary_fold_span_for_multi_element_chain() {
+    let _: bool = (0..3).map(|x| 2 * x).any(|x| x > 2);
+}
+
+/// Calls which should not trigger the `UNNECESSARY_FOLD` lint
+fn unnecessary_fold_should_ignore() {
+    let _ = (0..3).fold(true, |acc, x| acc || x > 2);
+    let _ = (0..3).fold(false, |acc, x| acc && x > 2);
+    let _ = (0..3).fold(1, |acc, x| acc + x);
+    let _ = (0..3).fold(0, |acc, x| acc * x);
+    let _ = (0..3).fold(0, |acc, x| 1 + acc + x);
+
+    // We only match against an accumulator on the left
+    // hand side. We could lint for .sum and .product when
+    // it's on the right, but don't for now (and this wouldn't
+    // be valid if we extended the lint to cover arbitrary numeric
+    // types).
+    let _ = (0..3).fold(false, |acc, x| x > 2 || acc);
+    let _ = (0..3).fold(true, |acc, x| x > 2 && acc);
+    let _ = (0..3).fold(0, |acc, x| x + acc);
+    let _ = (0..3).fold(1, |acc, x| x * acc);
+
+    let _ = [(0..2), (0..3)].iter().fold(0, |a, b| a + b.len());
+    let _ = [(0..2), (0..3)].iter().fold(1, |a, b| a * b.len());
+}
+
+fn main() {}

tests/ui/unnecessary_fold.rs

@@ -1,18 +1,22 @@
+// run-rustfix
+
+#![allow(dead_code)]
+
 /// Calls which should trigger the `UNNECESSARY_FOLD` lint
 fn unnecessary_fold() {
     // Can be replaced by .any
     let _ = (0..3).fold(false, |acc, x| acc || x > 2);
     // Can be replaced by .all
     let _ = (0..3).fold(true, |acc, x| acc && x > 2);
     // Can be replaced by .sum
-    let _ = (0..3).fold(0, |acc, x| acc + x);
+    let _: i32 = (0..3).fold(0, |acc, x| acc + x);
     // Can be replaced by .product
-    let _ = (0..3).fold(1, |acc, x| acc * x);
+    let _: i32 = (0..3).fold(1, |acc, x| acc * x);
 }
 
 /// Should trigger the `UNNECESSARY_FOLD` lint, with an error span including exactly `.fold(...)`
 fn unnecessary_fold_span_for_multi_element_chain() {
-    let _ = (0..3).map(|x| 2 * x).fold(false, |acc, x| acc || x > 2);
+    let _: bool = (0..3).map(|x| 2 * x).fold(false, |acc, x| acc || x > 2);
 }
 
 /// Calls which should not trigger the `UNNECESSARY_FOLD` lint

tests/ui/unnecessary_fold.stderr

@@ -1,34 +1,34 @@
 error: this `.fold` can be written more succinctly using another method
-  --> $DIR/unnecessary_fold.rs:4:19
+  --> $DIR/unnecessary_fold.rs:8:19
    |
 LL |     let _ = (0..3).fold(false, |acc, x| acc || x > 2);
    |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `.any(|x| x > 2)`
    |
    = note: `-D clippy::unnecessary-fold` implied by `-D warnings`
 
 error: this `.fold` can be written more succinctly using another method
-  --> $DIR/unnecessary_fold.rs:6:19
+  --> $DIR/unnecessary_fold.rs:10:19
    |
 LL |     let _ = (0..3).fold(true, |acc, x| acc && x > 2);
    |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `.all(|x| x > 2)`
 
 error: this `.fold` can be written more succinctly using another method
-  --> $DIR/unnecessary_fold.rs:8:19
+  --> $DIR/unnecessary_fold.rs:12:24
    |
-LL |     let _ = (0..3).fold(0, |acc, x| acc + x);
-   |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `.sum()`
+LL |     let _: i32 = (0..3).fold(0, |acc, x| acc + x);
+   |                        ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `.sum()`
 
 error: this `.fold` can be written more succinctly using another method
-  --> $DIR/unnecessary_fold.rs:10:19
+  --> $DIR/unnecessary_fold.rs:14:24
    |
-LL |     let _ = (0..3).fold(1, |acc, x| acc * x);
-   |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `.product()`
+LL |     let _: i32 = (0..3).fold(1, |acc, x| acc * x);
+   |                        ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `.product()`
 
 error: this `.fold` can be written more succinctly using another method
-  --> $DIR/unnecessary_fold.rs:15:34
+  --> $DIR/unnecessary_fold.rs:19:40
    |
-LL |     let _ = (0..3).map(|x| 2 * x).fold(false, |acc, x| acc || x > 2);
-   |                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `.any(|x| x > 2)`
+LL |     let _: bool = (0..3).map(|x| 2 * x).fold(false, |acc, x| acc || x > 2);
+   |                                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `.any(|x| x > 2)`
 
 error: aborting due to 5 previous errors