Replace match_method_chain() with method_chain_args()

src/utils.rs

@@ -8,10 +8,13 @@ use rustc::middle::ty;
 use std::borrow::Cow;
 use syntax::ast::Lit_::*;
 use syntax::ast;
+use syntax::ptr::P;
 
 use rustc::session::Session;
 use std::str::FromStr;
 
+pub type MethodArgs = HirVec<P<Expr>>;
+
 // module DefPaths for certain structs/enums we check for
 pub const OPTION_PATH: [&'static str; 3] = ["core", "option", "Option"];
 pub const RESULT_PATH: [&'static str; 3] = ["core", "result", "Result"];
@@ -164,24 +167,28 @@ pub fn match_path_ast(path: &ast::Path, segments: &[&str]) -> bool {
         |(a, b)| a.identifier.name.as_str() == *b)
 }
 
-/// match an Expr against a chain of methods. For example, if `expr` represents the `.baz()` in
-/// `foo.bar().baz()`, `matched_method_chain(expr, &["bar", "baz"])` will return true.
-pub fn match_method_chain(expr: &Expr, methods: &[&str]) -> bool {
-    let mut current = &expr.node ;
+/// match an Expr against a chain of methods, and return the matched Exprs. For example, if `expr`
+/// represents the `.baz()` in `foo.bar().baz()`, `matched_method_chain(expr, &["bar", "baz"])`
+/// will return a Vec containing the Exprs for `.bar()` and `.baz()`
+pub fn method_chain_args<'a>(expr: &'a Expr, methods: &[&str]) -> Option<Vec<&'a MethodArgs>> {
+    let mut current = expr;
+    let mut matched = Vec::with_capacity(methods.len());
     for method_name in methods.iter().rev() { // method chains are stored last -> first
-        if let ExprMethodCall(ref name, _, ref args) = *current {
+        if let ExprMethodCall(ref name, _, ref args) = current.node {
             if name.node.as_str() == *method_name {
-                current = &args[0].node
+                matched.push(args); // build up `matched` backwards
+                current = &args[0] // go to parent expression
             }
             else {
-                return false;
+                return None;
             }
         }
         else {
-            return false;
+            return None;
         }
     }
-    true
+    matched.reverse(); // reverse `matched`, so that it is in the same order as `methods`
+    Some(matched)
 }