Fix vec_init_then_push FP

clippy_lints/src/vec_init_then_push.rs

@@ -83,8 +83,11 @@ impl VecPushSearcher {
 }
 
 impl LateLintPass<'_> for VecInitThenPush {
-    fn check_local(&mut self, cx: &LateContext<'tcx>, local: &'tcx Local<'tcx>) {
+    fn check_block(&mut self, _: &LateContext<'tcx>, _: &'tcx Block<'tcx>) {
         self.searcher = None;
+    }
+
+    fn check_local(&mut self, cx: &LateContext<'tcx>, local: &'tcx Local<'tcx>) {
         if_chain! {
             if !in_external_macro(cx.sess(), local.span);
             if let Some(init) = local.init;

tests/ui/vec_init_then_push.rs

@@ -12,10 +12,35 @@ fn main() {
     cap_err.push(0);
     cap_err.push(1);
     cap_err.push(2);
+    if true {
+        // don't include this one
+        cap_err.push(3);
+    }
 
     let mut cap_ok = Vec::with_capacity(10);
     cap_ok.push(0);
 
     new_err = Vec::new();
     new_err.push(0);
+
+    let mut vec = Vec::new();
+    // control flow at block final expression
+    if true {
+        // no lint
+        vec.push(1);
+    }
+}
+
+pub fn no_lint() -> Vec<i32> {
+    let mut p = Some(1);
+    let mut vec = Vec::new();
+    loop {
+        match p {
+            None => return vec,
+            Some(i) => {
+                vec.push(i);
+                p = None;
+            },
+        }
+    }
 }

tests/ui/vec_init_then_push.stderr

@@ -24,7 +24,7 @@ LL | |     cap_err.push(2);
    | |____________________^ help: consider using the `vec![]` macro: `let mut cap_err = vec![..];`
 
 error: calls to `push` immediately after creation
-  --> $DIR/vec_init_then_push.rs:19:5
+  --> $DIR/vec_init_then_push.rs:23:5
    |
 LL | /     new_err = Vec::new();
 LL | |     new_err.push(0);