add more test coverage for #11230 (#13915)

Closes #11230

changelog:  none

Author: y21

Diff for: tests/ui/crashes/ice-11230.fixed

@@ -0,0 +1,16 @@
+// Test for https://github.com/rust-lang/rust-clippy/issues/11230
+#![warn(clippy::explicit_iter_loop)]
+#![warn(clippy::needless_collect)]
+
+// explicit_iter_loop
+fn main() {
+    const A: &[for<'a> fn(&'a ())] = &[];
+    for v in A {}
+}
+
+// needless_collect
+trait Helper<'a>: Iterator<Item = fn()> {}
+
+fn x(w: &mut dyn for<'a> Helper<'a>) {
+    w.next().is_none();
+}

Diff for: tests/ui/crashes/ice-11230.rs

@@ -1,6 +1,16 @@
 // Test for https://github.com/rust-lang/rust-clippy/issues/11230
+#![warn(clippy::explicit_iter_loop)]
+#![warn(clippy::needless_collect)]
 
+// explicit_iter_loop
 fn main() {
     const A: &[for<'a> fn(&'a ())] = &[];
     for v in A.iter() {}
 }
+
+// needless_collect
+trait Helper<'a>: Iterator<Item = fn()> {}
+
+fn x(w: &mut dyn for<'a> Helper<'a>) {
+    w.collect::<Vec<_>>().is_empty();
+}

Diff for: tests/ui/crashes/ice-11230.stderr

@@ -0,0 +1,20 @@
+error: it is more concise to loop over references to containers instead of using explicit iteration methods
+  --> tests/ui/crashes/ice-11230.rs:8:14
+   |
+LL |     for v in A.iter() {}
+   |              ^^^^^^^^ help: to write this more concisely, try: `A`
+   |
+   = note: `-D clippy::explicit-iter-loop` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::explicit_iter_loop)]`
+
+error: avoid using `collect()` when not needed
+  --> tests/ui/crashes/ice-11230.rs:15:7
+   |
+LL |     w.collect::<Vec<_>>().is_empty();
+   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `next().is_none()`
+   |
+   = note: `-D clippy::needless-collect` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::needless_collect)]`
+
+error: aborting due to 2 previous errors
+