Rust: Implement good suggestions from ql-for-ql.

Author: geoffw0

rust/ql/lib/codeql/rust/frameworks/Reqwest.qll

@@ -9,11 +9,11 @@ private import codeql.rust.Concepts
  * A call to `reqwest::get` or `reqwest::blocking::get`.
  */
 private class ReqwestGet extends RemoteSource::Range {
-  CallExpr ce;
-
   ReqwestGet() {
-    this.asExpr().getExpr() = ce and
-    ce.getExpr().(PathExpr).getPath().getResolvedCrateOrigin().matches("%reqwest") and
-    ce.getExpr().(PathExpr).getPath().getResolvedPath() = ["crate::get", "crate::blocking::get"]
+    exists(CallExpr ce |
+      this.asExpr().getExpr() = ce and
+      ce.getExpr().(PathExpr).getPath().getResolvedCrateOrigin().matches("%reqwest") and
+      ce.getExpr().(PathExpr).getPath().getResolvedPath() = ["crate::get", "crate::blocking::get"]
+    )
   }
 }