From 60dd2b65dcb10f10c02e90300941bc698fa4a39b Mon Sep 17 00:00:00 2001
From: Jason Newcomb <jsnewcomb@pm.me>
Date: Fri, 21 May 2021 15:42:57 -0400
Subject: [PATCH] Fix `redundant_closure` for `vec![]` macro in a closure with
 arguments

---
 clippy_lints/src/eta_reduction.rs | 24 +++++++++++++-----------
 tests/ui/eta.fixed                |  3 +++
 tests/ui/eta.rs                   |  3 +++
 tests/ui/eta.stderr               | 16 ++++++++--------
 4 files changed, 27 insertions(+), 19 deletions(-)

diff --git a/clippy_lints/src/eta_reduction.rs b/clippy_lints/src/eta_reduction.rs
index 2f1aa53236d..afc5d546474 100644
--- a/clippy_lints/src/eta_reduction.rs
+++ b/clippy_lints/src/eta_reduction.rs
@@ -92,17 +92,19 @@ fn check_closure(cx: &LateContext<'_>, expr: &Expr<'_>) {
         let ex = &body.value;
 
         if ex.span.ctxt() != expr.span.ctxt() {
-            if let Some(VecArgs::Vec(&[])) = higher::vec_macro(cx, ex) {
-                // replace `|| vec![]` with `Vec::new`
-                span_lint_and_sugg(
-                    cx,
-                    REDUNDANT_CLOSURE,
-                    expr.span,
-                    "redundant closure",
-                    "replace the closure with `Vec::new`",
-                    "std::vec::Vec::new".into(),
-                    Applicability::MachineApplicable,
-                );
+            if decl.inputs.is_empty() {
+                if let Some(VecArgs::Vec(&[])) = higher::vec_macro(cx, ex) {
+                    // replace `|| vec![]` with `Vec::new`
+                    span_lint_and_sugg(
+                        cx,
+                        REDUNDANT_CLOSURE,
+                        expr.span,
+                        "redundant closure",
+                        "replace the closure with `Vec::new`",
+                        "std::vec::Vec::new".into(),
+                        Applicability::MachineApplicable,
+                    );
+                }
             }
             // skip `foo(|| macro!())`
             return;
diff --git a/tests/ui/eta.fixed b/tests/ui/eta.fixed
index 2be2283e3fd..9e752311c67 100644
--- a/tests/ui/eta.fixed
+++ b/tests/ui/eta.fixed
@@ -48,6 +48,9 @@ fn main() {
     // See #515
     let a: Option<Box<dyn (::std::ops::Deref<Target = [i32]>)>> =
         Some(vec![1i32, 2]).map(|v| -> Box<dyn (::std::ops::Deref<Target = [i32]>)> { Box::new(v) });
+
+    // issue #7224
+    let _: Option<Vec<u32>> = Some(0).map(|_| vec![]);
 }
 
 trait TestTrait {
diff --git a/tests/ui/eta.rs b/tests/ui/eta.rs
index f0373f9ccf6..44be4628cbd 100644
--- a/tests/ui/eta.rs
+++ b/tests/ui/eta.rs
@@ -48,6 +48,9 @@ fn main() {
     // See #515
     let a: Option<Box<dyn (::std::ops::Deref<Target = [i32]>)>> =
         Some(vec![1i32, 2]).map(|v| -> Box<dyn (::std::ops::Deref<Target = [i32]>)> { Box::new(v) });
+
+    // issue #7224
+    let _: Option<Vec<u32>> = Some(0).map(|_| vec![]);
 }
 
 trait TestTrait {
diff --git a/tests/ui/eta.stderr b/tests/ui/eta.stderr
index 57ed6527966..8795d3b42c6 100644
--- a/tests/ui/eta.stderr
+++ b/tests/ui/eta.stderr
@@ -33,7 +33,7 @@ LL |     let e = Some(1u8).map(|a| generic(a));
    |                           ^^^^^^^^^^^^^^ help: replace the closure with the function itself: `generic`
 
 error: redundant closure
-  --> $DIR/eta.rs:89:51
+  --> $DIR/eta.rs:92:51
    |
 LL |     let e = Some(TestStruct { some_ref: &i }).map(|a| a.foo());
    |                                                   ^^^^^^^^^^^ help: replace the closure with the method itself: `TestStruct::foo`
@@ -41,43 +41,43 @@ LL |     let e = Some(TestStruct { some_ref: &i }).map(|a| a.foo());
    = note: `-D clippy::redundant-closure-for-method-calls` implied by `-D warnings`
 
 error: redundant closure
-  --> $DIR/eta.rs:91:51
+  --> $DIR/eta.rs:94:51
    |
 LL |     let e = Some(TestStruct { some_ref: &i }).map(|a| a.trait_foo());
    |                                                   ^^^^^^^^^^^^^^^^^ help: replace the closure with the method itself: `TestTrait::trait_foo`
 
 error: redundant closure
-  --> $DIR/eta.rs:94:42
+  --> $DIR/eta.rs:97:42
    |
 LL |     let e = Some(&mut vec![1, 2, 3]).map(|v| v.clear());
    |                                          ^^^^^^^^^^^^^ help: replace the closure with the method itself: `std::vec::Vec::clear`
 
 error: redundant closure
-  --> $DIR/eta.rs:99:29
+  --> $DIR/eta.rs:102:29
    |
 LL |     let e = Some("str").map(|s| s.to_string());
    |                             ^^^^^^^^^^^^^^^^^ help: replace the closure with the method itself: `std::string::ToString::to_string`
 
 error: redundant closure
-  --> $DIR/eta.rs:101:27
+  --> $DIR/eta.rs:104:27
    |
 LL |     let e = Some('a').map(|s| s.to_uppercase());
    |                           ^^^^^^^^^^^^^^^^^^^^ help: replace the closure with the method itself: `char::to_uppercase`
 
 error: redundant closure
-  --> $DIR/eta.rs:104:65
+  --> $DIR/eta.rs:107:65
    |
 LL |     let e: std::vec::Vec<char> = vec!['a', 'b', 'c'].iter().map(|c| c.to_ascii_uppercase()).collect();
    |                                                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace the closure with the method itself: `char::to_ascii_uppercase`
 
 error: redundant closure
-  --> $DIR/eta.rs:187:27
+  --> $DIR/eta.rs:190:27
    |
 LL |     let a = Some(1u8).map(|a| foo_ptr(a));
    |                           ^^^^^^^^^^^^^^ help: replace the closure with the function itself: `foo_ptr`
 
 error: redundant closure
-  --> $DIR/eta.rs:192:27
+  --> $DIR/eta.rs:195:27
    |
 LL |     let a = Some(1u8).map(|a| closure(a));
    |                           ^^^^^^^^^^^^^^ help: replace the closure with the function itself: `closure`