add tests for issue rust-lang#11861

Author: ericwu17

tests/ui/vec.fixed

@@ -176,3 +176,20 @@ fn below() {
         let _: String = a;
     }
 }
+
+fn func_needing_vec(_bar: usize, _baz: Vec<usize>) {}
+fn func_not_needing_vec(_bar: usize, _baz: usize) {}
+
+fn issue11861() {
+    macro_rules! this_macro_needs_vec {
+        ($x:expr) => {{ func_needing_vec($x.iter().sum(), $x) }};
+    }
+    macro_rules! this_macro_doesnt_need_vec {
+        ($x:expr) => {{ func_not_needing_vec($x.iter().sum(), $x.iter().sum()) }};
+    }
+
+    // Do not lint the next line
+    this_macro_needs_vec!(vec![1]);
+    // Lint the next line
+    this_macro_doesnt_need_vec!([1]);
+}

tests/ui/vec.rs

@@ -176,3 +176,20 @@ fn below() {
         let _: String = a;
     }
 }
+
+fn func_needing_vec(_bar: usize, _baz: Vec<usize>) {}
+fn func_not_needing_vec(_bar: usize, _baz: usize) {}
+
+fn issue11861() {
+    macro_rules! this_macro_needs_vec {
+        ($x:expr) => {{ func_needing_vec($x.iter().sum(), $x) }};
+    }
+    macro_rules! this_macro_doesnt_need_vec {
+        ($x:expr) => {{ func_not_needing_vec($x.iter().sum(), $x.iter().sum()) }};
+    }
+
+    // Do not lint the next line
+    this_macro_needs_vec!(vec![1]);
+    // Lint the next line
+    this_macro_doesnt_need_vec!(vec![1]);
+}

tests/ui/vec.stderr

@@ -115,5 +115,11 @@ error: useless use of `vec!`
 LL |     for a in vec![String::new(), String::new()] {
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: you can use an array directly: `[String::new(), String::new()]`
 
-error: aborting due to 19 previous errors
+error: useless use of `vec!`
+  --> $DIR/vec.rs:194:33
+   |
+LL |     this_macro_doesnt_need_vec!(vec![1]);
+   |                                 ^^^^^^^ help: you can use an array directly: `[1]`
+
+error: aborting due to 20 previous errors