Auto merge of #6871 - camsteffen:redundant-closure-macro, r=Manishearth

Fix redundant closure with macros

changelog: Fix redundant_closure FPs with macros

Fixes #6732
Fixes #6850
Fixes #4354 (addresses the error message confusion)

3 files changed, 71 insertions, 35 deletions

diff --git a/tests/ui/eta.fixed b/tests/ui/eta.fixed
index 1b34c2f74eb..2be2283e3fd 100644
--- a/tests/ui/eta.fixed
+++ b/tests/ui/eta.fixed
@@ -16,10 +16,25 @@
 
 use std::path::PathBuf;
 
+macro_rules! mac {
+    () => {
+        foobar()
+    };
+}
+
+macro_rules! closure_mac {
+    () => {
+        |n| foo(n)
+    };
+}
+
 fn main() {
     let a = Some(1u8).map(foo);
     meta(foo);
     let c = Some(1u8).map(|a| {1+2; foo}(a));
+    true.then(|| mac!()); // don't lint function in macro expansion
+    Some(1).map(closure_mac!()); // don't lint closure in macro expansion
+    let _: Option<Vec<u8>> = true.then(std::vec::Vec::new); // special case vec!
     let d = Some(1u8).map(|a| foo((|b| foo2(b))(a))); //is adjusted?
     all(&[1, 2, 3], &2, |x, y| below(x, y)); //is adjusted
     unsafe {
diff --git a/tests/ui/eta.rs b/tests/ui/eta.rs
index 4f050bd8479..f0373f9ccf6 100644
--- a/tests/ui/eta.rs
+++ b/tests/ui/eta.rs
@@ -16,10 +16,25 @@
 
 use std::path::PathBuf;
 
+macro_rules! mac {
+    () => {
+        foobar()
+    };
+}
+
+macro_rules! closure_mac {
+    () => {
+        |n| foo(n)
+    };
+}
+
 fn main() {
     let a = Some(1u8).map(|a| foo(a));
     meta(|a| foo(a));
     let c = Some(1u8).map(|a| {1+2; foo}(a));
+    true.then(|| mac!()); // don't lint function in macro expansion
+    Some(1).map(closure_mac!()); // don't lint closure in macro expansion
+    let _: Option<Vec<u8>> = true.then(|| vec![]); // special case vec!
     let d = Some(1u8).map(|a| foo((|b| foo2(b))(a))); //is adjusted?
     all(&[1, 2, 3], &&2, |x, y| below(x, y)); //is adjusted
     unsafe {
diff --git a/tests/ui/eta.stderr b/tests/ui/eta.stderr
index 16aa1b07733..57ed6527966 100644
--- a/tests/ui/eta.stderr
+++ b/tests/ui/eta.stderr
@@ -1,80 +1,86 @@
-error: redundant closure found
-  --> $DIR/eta.rs:20:27
+error: redundant closure
+  --> $DIR/eta.rs:32:27
    |
 LL |     let a = Some(1u8).map(|a| foo(a));
-   |                           ^^^^^^^^^^ help: remove closure as shown: `foo`
+   |                           ^^^^^^^^^^ help: replace the closure with the function itself: `foo`
    |
    = note: `-D clippy::redundant-closure` implied by `-D warnings`
 
-error: redundant closure found
-  --> $DIR/eta.rs:21:10
+error: redundant closure
+  --> $DIR/eta.rs:33:10
    |
 LL |     meta(|a| foo(a));
-   |          ^^^^^^^^^^ help: remove closure as shown: `foo`
+   |          ^^^^^^^^^^ help: replace the closure with the function itself: `foo`
+
+error: redundant closure
+  --> $DIR/eta.rs:37:40
+   |
+LL |     let _: Option<Vec<u8>> = true.then(|| vec![]); // special case vec!
+   |                                        ^^^^^^^^^ help: replace the closure with `Vec::new`: `std::vec::Vec::new`
 
 error: this expression borrows a reference (`&u8`) that is immediately dereferenced by the compiler
-  --> $DIR/eta.rs:24:21
+  --> $DIR/eta.rs:39:21
    |
 LL |     all(&[1, 2, 3], &&2, |x, y| below(x, y)); //is adjusted
    |                     ^^^ help: change this to: `&2`
    |
    = note: `-D clippy::needless-borrow` implied by `-D warnings`
 
-error: redundant closure found
-  --> $DIR/eta.rs:31:27
+error: redundant closure
+  --> $DIR/eta.rs:46:27
    |
 LL |     let e = Some(1u8).map(|a| generic(a));
-   |                           ^^^^^^^^^^^^^^ help: remove closure as shown: `generic`
+   |                           ^^^^^^^^^^^^^^ help: replace the closure with the function itself: `generic`
 
-error: redundant closure found
-  --> $DIR/eta.rs:74:51
+error: redundant closure
+  --> $DIR/eta.rs:89:51
    |
 LL |     let e = Some(TestStruct { some_ref: &i }).map(|a| a.foo());
-   |                                                   ^^^^^^^^^^^ help: remove closure as shown: `TestStruct::foo`
+   |                                                   ^^^^^^^^^^^ help: replace the closure with the method itself: `TestStruct::foo`
    |
    = note: `-D clippy::redundant-closure-for-method-calls` implied by `-D warnings`
 
-error: redundant closure found
-  --> $DIR/eta.rs:76:51
+error: redundant closure
+  --> $DIR/eta.rs:91:51
    |
 LL |     let e = Some(TestStruct { some_ref: &i }).map(|a| a.trait_foo());
-   |                                                   ^^^^^^^^^^^^^^^^^ help: remove closure as shown: `TestTrait::trait_foo`
+   |                                                   ^^^^^^^^^^^^^^^^^ help: replace the closure with the method itself: `TestTrait::trait_foo`
 
-error: redundant closure found
-  --> $DIR/eta.rs:79:42
+error: redundant closure
+  --> $DIR/eta.rs:94:42
    |
 LL |     let e = Some(&mut vec![1, 2, 3]).map(|v| v.clear());
-   |                                          ^^^^^^^^^^^^^ help: remove closure as shown: `std::vec::Vec::clear`
+   |                                          ^^^^^^^^^^^^^ help: replace the closure with the method itself: `std::vec::Vec::clear`
 
-error: redundant closure found
-  --> $DIR/eta.rs:84:29
+error: redundant closure
+  --> $DIR/eta.rs:99:29
    |
 LL |     let e = Some("str").map(|s| s.to_string());
-   |                             ^^^^^^^^^^^^^^^^^ help: remove closure as shown: `std::string::ToString::to_string`
+   |                             ^^^^^^^^^^^^^^^^^ help: replace the closure with the method itself: `std::string::ToString::to_string`
 
-error: redundant closure found
-  --> $DIR/eta.rs:86:27
+error: redundant closure
+  --> $DIR/eta.rs:101:27
    |
 LL |     let e = Some('a').map(|s| s.to_uppercase());
-   |                           ^^^^^^^^^^^^^^^^^^^^ help: remove closure as shown: `char::to_uppercase`
+   |                           ^^^^^^^^^^^^^^^^^^^^ help: replace the closure with the method itself: `char::to_uppercase`
 
-error: redundant closure found
-  --> $DIR/eta.rs:89:65
+error: redundant closure
+  --> $DIR/eta.rs:104:65
    |
 LL |     let e: std::vec::Vec<char> = vec!['a', 'b', 'c'].iter().map(|c| c.to_ascii_uppercase()).collect();
-   |                                                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: remove closure as shown: `char::to_ascii_uppercase`
+   |                                                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace the closure with the method itself: `char::to_ascii_uppercase`
 
-error: redundant closure found
-  --> $DIR/eta.rs:172:27
+error: redundant closure
+  --> $DIR/eta.rs:187:27
    |
 LL |     let a = Some(1u8).map(|a| foo_ptr(a));
-   |                           ^^^^^^^^^^^^^^ help: remove closure as shown: `foo_ptr`
+   |                           ^^^^^^^^^^^^^^ help: replace the closure with the function itself: `foo_ptr`
 
-error: redundant closure found
-  --> $DIR/eta.rs:177:27
+error: redundant closure
+  --> $DIR/eta.rs:192:27
    |
 LL |     let a = Some(1u8).map(|a| closure(a));
-   |                           ^^^^^^^^^^^^^^ help: remove closure as shown: `closure`
+   |                           ^^^^^^^^^^^^^^ help: replace the closure with the function itself: `closure`
 
-error: aborting due to 12 previous errors
+error: aborting due to 13 previous errors