Fix unnecessary_fold bug

clippy_lints/src/methods.rs

@@ -12,8 +12,8 @@ use syntax::ast;
 use syntax::codemap::{Span, BytePos};
 use utils::{get_arg_name, get_trait_def_id, implements_trait, in_external_macro, in_macro, is_copy, is_self, is_self_ty,
             iter_input_pats, last_path_segment, match_def_path, match_path, match_qpath, match_trait_method,
-            match_type, method_chain_args, return_ty, remove_blocks, same_tys, single_segment_path, snippet, span_lint,
-            span_lint_and_sugg, span_lint_and_then, span_note_and_lint, walk_ptrs_ty, walk_ptrs_ty_depth};
+            match_type, method_chain_args, match_var, return_ty, remove_blocks, same_tys, single_segment_path, snippet,
+            span_lint, span_lint_and_sugg, span_lint_and_then, span_note_and_lint, walk_ptrs_ty, walk_ptrs_ty_depth};
 use utils::paths;
 use utils::sugg;
 use utils::const_to_u64;
@@ -1162,8 +1162,8 @@ fn lint_unnecessary_fold(cx: &LateContext, expr: &hir::Expr, fold_args: &[hir::E
             if let Some(first_arg_ident) = get_arg_name(&closure_body.arguments[0].pat);
             if let Some(second_arg_ident) = get_arg_name(&closure_body.arguments[1].pat);
 
-            if let hir::ExprPath(hir::QPath::Resolved(None, ref path)) = left_expr.node;
-            if path.segments.len() == 1 && &path.segments[0].name == &first_arg_ident;
+            if match_var(&*left_expr, first_arg_ident);
+            if replacement_has_args || match_var(&*right_expr, second_arg_ident);
 
             then {
                 // Span containing `.fold(...)`

tests/ui/methods.rs

@@ -419,6 +419,9 @@ fn unnecessary_fold_should_ignore() {
     let _ = (0..3).fold(true, |acc, x| x > 2 && acc);
     let _ = (0..3).fold(0, |acc, x| x + acc);
     let _ = (0..3).fold(1, |acc, x| x * acc);
+
+    let _ = [(0..2), (0..3)].iter().fold(0, |a, b| a + b.len());
+    let _ = [(0..2), (0..3)].iter().fold(1, |a, b| a * b.len());
 }
 
 #[allow(similar_names)]

tests/ui/methods.stderr

@@ -526,9 +526,9 @@ error: this `.fold` can be written more succinctly using another method
     |                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `.any(|x| x > 2)`
 
 error: used unwrap() on an Option value. If you don't want to handle the None case gracefully, consider using expect() to provide a better panic message
-   --> $DIR/methods.rs:427:13
+   --> $DIR/methods.rs:430:13
     |
-427 |     let _ = opt.unwrap();
+430 |     let _ = opt.unwrap();
     |             ^^^^^^^^^^^^
     |
     = note: `-D option-unwrap-used` implied by `-D warnings`