Auto merge of #9126 - Jarcho:auto_deref_sugg, r=Manishearth

`explicit_auto_deref` changes

fixes #9123
fixes #9109
fixes #9143
fixes #9101

This avoid suggesting code which hits a rustc bug. Basically `&{x}` won't use auto-deref if the target type is `Sized`.

changelog: Don't suggest using auto deref for block expressions when the target type is `Sized`
changelog: Include the borrow in the suggestion for `explicit_auto_deref`
changelog: Don't lint `explicit_auto_deref` on `dyn Trait` return
changelog: Don't lint `explicit_auto_deref` when other adjustments are required
changelog: Lint `explicit_auto_deref` in implicit return positions for closures

3 files changed, 192 insertions, 54 deletions

diff --git a/tests/ui/explicit_auto_deref.fixed b/tests/ui/explicit_auto_deref.fixed
index a650fdc1f89..d1d35e5c0eb 100644
--- a/tests/ui/explicit_auto_deref.fixed
+++ b/tests/ui/explicit_auto_deref.fixed
@@ -1,5 +1,6 @@
 // run-rustfix
 
+#![feature(closure_lifetime_binder)]
 #![warn(clippy::explicit_auto_deref)]
 #![allow(
     dead_code,
@@ -67,6 +68,8 @@ fn main() {
     let s = String::new();
 
     let _: &str = &s;
+    let _: &str = &{ String::new() };
+    let _: &str = &mut { String::new() };
     let _ = &*s; // Don't lint. Inferred type would change.
     let _: &_ = &*s; // Don't lint. Inferred type would change.
 
@@ -215,4 +218,52 @@ fn main() {
     let s = &"str";
     let _ = || return *s;
     let _ = || -> &'static str { return s };
+
+    struct X;
+    struct Y(X);
+    impl core::ops::Deref for Y {
+        type Target = X;
+        fn deref(&self) -> &Self::Target {
+            &self.0
+        }
+    }
+    let _: &X = &*{ Y(X) };
+    let _: &X = &*match 0 {
+        #[rustfmt::skip]
+        0 => { Y(X) },
+        _ => panic!(),
+    };
+    let _: &X = &*if true { Y(X) } else { panic!() };
+
+    fn deref_to_u<U, T: core::ops::Deref<Target = U>>(x: &T) -> &U {
+        x
+    }
+
+    let _ = |x: &'static Box<dyn Iterator<Item = u32>>| -> &'static dyn Iterator<Item = u32> { &**x };
+    fn ret_any(x: &Box<dyn std::any::Any>) -> &dyn std::any::Any {
+        &**x
+    }
+
+    let x = String::new();
+    let _: *const str = &*x;
+
+    struct S7([u32; 1]);
+    impl core::ops::Deref for S7 {
+        type Target = [u32; 1];
+        fn deref(&self) -> &Self::Target {
+            &self.0
+        }
+    }
+    let x = S7([0]);
+    let _: &[u32] = &*x;
+
+    let c1 = |_: &Vec<&u32>| {};
+    let x = &&vec![&1u32];
+    c1(x);
+    let _ = for<'a, 'b> |x: &'a &'a Vec<&'b u32>, b: bool| -> &'a Vec<&'b u32> {
+        if b {
+            return x;
+        }
+        x
+    };
 }
diff --git a/tests/ui/explicit_auto_deref.rs b/tests/ui/explicit_auto_deref.rs
index 8f4f352576a..deedafad153 100644
--- a/tests/ui/explicit_auto_deref.rs
+++ b/tests/ui/explicit_auto_deref.rs
@@ -1,5 +1,6 @@
 // run-rustfix
 
+#![feature(closure_lifetime_binder)]
 #![warn(clippy::explicit_auto_deref)]
 #![allow(
     dead_code,
@@ -67,6 +68,8 @@ fn main() {
     let s = String::new();
 
     let _: &str = &*s;
+    let _: &str = &*{ String::new() };
+    let _: &str = &mut *{ String::new() };
     let _ = &*s; // Don't lint. Inferred type would change.
     let _: &_ = &*s; // Don't lint. Inferred type would change.
 
@@ -215,4 +218,52 @@ fn main() {
     let s = &"str";
     let _ = || return *s;
     let _ = || -> &'static str { return *s };
+
+    struct X;
+    struct Y(X);
+    impl core::ops::Deref for Y {
+        type Target = X;
+        fn deref(&self) -> &Self::Target {
+            &self.0
+        }
+    }
+    let _: &X = &*{ Y(X) };
+    let _: &X = &*match 0 {
+        #[rustfmt::skip]
+        0 => { Y(X) },
+        _ => panic!(),
+    };
+    let _: &X = &*if true { Y(X) } else { panic!() };
+
+    fn deref_to_u<U, T: core::ops::Deref<Target = U>>(x: &T) -> &U {
+        &**x
+    }
+
+    let _ = |x: &'static Box<dyn Iterator<Item = u32>>| -> &'static dyn Iterator<Item = u32> { &**x };
+    fn ret_any(x: &Box<dyn std::any::Any>) -> &dyn std::any::Any {
+        &**x
+    }
+
+    let x = String::new();
+    let _: *const str = &*x;
+
+    struct S7([u32; 1]);
+    impl core::ops::Deref for S7 {
+        type Target = [u32; 1];
+        fn deref(&self) -> &Self::Target {
+            &self.0
+        }
+    }
+    let x = S7([0]);
+    let _: &[u32] = &*x;
+
+    let c1 = |_: &Vec<&u32>| {};
+    let x = &&vec![&1u32];
+    c1(*x);
+    let _ = for<'a, 'b> |x: &'a &'a Vec<&'b u32>, b: bool| -> &'a Vec<&'b u32> {
+        if b {
+            return *x;
+        }
+        *x
+    };
 }
diff --git a/tests/ui/explicit_auto_deref.stderr b/tests/ui/explicit_auto_deref.stderr
index 92765307ea7..91863abcc5d 100644
--- a/tests/ui/explicit_auto_deref.stderr
+++ b/tests/ui/explicit_auto_deref.stderr
@@ -1,202 +1,238 @@
 error: deref which would be done by auto-deref
-  --> $DIR/explicit_auto_deref.rs:69:20
+  --> $DIR/explicit_auto_deref.rs:70:19
    |
 LL |     let _: &str = &*s;
-   |                    ^^ help: try this: `s`
+   |                   ^^^ help: try this: `&s`
    |
    = note: `-D clippy::explicit-auto-deref` implied by `-D warnings`
 
 error: deref which would be done by auto-deref
-  --> $DIR/explicit_auto_deref.rs:73:12
+  --> $DIR/explicit_auto_deref.rs:71:19
+   |
+LL |     let _: &str = &*{ String::new() };
+   |                   ^^^^^^^^^^^^^^^^^^^ help: try this: `&{ String::new() }`
+
+error: deref which would be done by auto-deref
+  --> $DIR/explicit_auto_deref.rs:72:19
+   |
+LL |     let _: &str = &mut *{ String::new() };
+   |                   ^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `&mut { String::new() }`
+
+error: deref which would be done by auto-deref
+  --> $DIR/explicit_auto_deref.rs:76:11
    |
 LL |     f_str(&*s);
-   |            ^^ help: try this: `s`
+   |           ^^^ help: try this: `&s`
 
 error: deref which would be done by auto-deref
-  --> $DIR/explicit_auto_deref.rs:77:14
+  --> $DIR/explicit_auto_deref.rs:80:13
    |
 LL |     f_str_t(&*s, &*s); // Don't lint second param.
-   |              ^^ help: try this: `s`
+   |             ^^^ help: try this: `&s`
 
 error: deref which would be done by auto-deref
-  --> $DIR/explicit_auto_deref.rs:80:25
+  --> $DIR/explicit_auto_deref.rs:83:24
    |
 LL |     let _: &Box<i32> = &**b;
-   |                         ^^^ help: try this: `b`
+   |                        ^^^^ help: try this: `&b`
 
 error: deref which would be done by auto-deref
-  --> $DIR/explicit_auto_deref.rs:86:8
+  --> $DIR/explicit_auto_deref.rs:89:7
    |
 LL |     c(&*s);
-   |        ^^ help: try this: `s`
+   |       ^^^ help: try this: `&s`
 
 error: deref which would be done by auto-deref
-  --> $DIR/explicit_auto_deref.rs:92:9
+  --> $DIR/explicit_auto_deref.rs:95:9
    |
 LL |         &**x
    |         ^^^^ help: try this: `x`
 
 error: deref which would be done by auto-deref
-  --> $DIR/explicit_auto_deref.rs:96:11
+  --> $DIR/explicit_auto_deref.rs:99:11
    |
 LL |         { &**x }
    |           ^^^^ help: try this: `x`
 
 error: deref which would be done by auto-deref
-  --> $DIR/explicit_auto_deref.rs:100:9
+  --> $DIR/explicit_auto_deref.rs:103:9
    |
 LL |         &**{ x }
    |         ^^^^^^^^ help: try this: `{ x }`
 
 error: deref which would be done by auto-deref
-  --> $DIR/explicit_auto_deref.rs:104:9
+  --> $DIR/explicit_auto_deref.rs:107:9
    |
 LL |         &***x
    |         ^^^^^ help: try this: `x`
 
 error: deref which would be done by auto-deref
-  --> $DIR/explicit_auto_deref.rs:121:13
+  --> $DIR/explicit_auto_deref.rs:124:12
    |
 LL |         f1(&*x);
-   |             ^^ help: try this: `x`
+   |            ^^^ help: try this: `&x`
 
 error: deref which would be done by auto-deref
-  --> $DIR/explicit_auto_deref.rs:122:13
+  --> $DIR/explicit_auto_deref.rs:125:12
    |
 LL |         f2(&*x);
-   |             ^^ help: try this: `x`
+   |            ^^^ help: try this: `&x`
 
 error: deref which would be done by auto-deref
-  --> $DIR/explicit_auto_deref.rs:123:13
+  --> $DIR/explicit_auto_deref.rs:126:12
    |
 LL |         f3(&*x);
-   |             ^^ help: try this: `x`
+   |            ^^^ help: try this: `&x`
 
 error: deref which would be done by auto-deref
-  --> $DIR/explicit_auto_deref.rs:124:28
+  --> $DIR/explicit_auto_deref.rs:127:27
    |
 LL |         f4.callable_str()(&*x);
-   |                            ^^ help: try this: `x`
+   |                           ^^^ help: try this: `&x`
 
 error: deref which would be done by auto-deref
-  --> $DIR/explicit_auto_deref.rs:125:13
+  --> $DIR/explicit_auto_deref.rs:128:12
    |
 LL |         f5(&*x);
-   |             ^^ help: try this: `x`
+   |            ^^^ help: try this: `&x`
 
 error: deref which would be done by auto-deref
-  --> $DIR/explicit_auto_deref.rs:126:13
+  --> $DIR/explicit_auto_deref.rs:129:12
    |
 LL |         f6(&*x);
-   |             ^^ help: try this: `x`
+   |            ^^^ help: try this: `&x`
 
 error: deref which would be done by auto-deref
-  --> $DIR/explicit_auto_deref.rs:127:28
+  --> $DIR/explicit_auto_deref.rs:130:27
    |
 LL |         f7.callable_str()(&*x);
-   |                            ^^ help: try this: `x`
+   |                           ^^^ help: try this: `&x`
 
 error: deref which would be done by auto-deref
-  --> $DIR/explicit_auto_deref.rs:128:26
+  --> $DIR/explicit_auto_deref.rs:131:25
    |
 LL |         f8.callable_t()(&*x);
-   |                          ^^ help: try this: `x`
+   |                         ^^^ help: try this: `&x`
 
 error: deref which would be done by auto-deref
-  --> $DIR/explicit_auto_deref.rs:129:13
+  --> $DIR/explicit_auto_deref.rs:132:12
    |
 LL |         f9(&*x);
-   |             ^^ help: try this: `x`
+   |            ^^^ help: try this: `&x`
 
 error: deref which would be done by auto-deref
-  --> $DIR/explicit_auto_deref.rs:130:14
+  --> $DIR/explicit_auto_deref.rs:133:13
    |
 LL |         f10(&*x);
-   |              ^^ help: try this: `x`
+   |             ^^^ help: try this: `&x`
 
 error: deref which would be done by auto-deref
-  --> $DIR/explicit_auto_deref.rs:131:27
+  --> $DIR/explicit_auto_deref.rs:134:26
    |
 LL |         f11.callable_t()(&*x);
-   |                           ^^ help: try this: `x`
+   |                          ^^^ help: try this: `&x`
 
 error: deref which would be done by auto-deref
-  --> $DIR/explicit_auto_deref.rs:135:17
+  --> $DIR/explicit_auto_deref.rs:138:16
    |
 LL |     let _ = S1(&*s);
-   |                 ^^ help: try this: `s`
+   |                ^^^ help: try this: `&s`
 
 error: deref which would be done by auto-deref
-  --> $DIR/explicit_auto_deref.rs:140:22
+  --> $DIR/explicit_auto_deref.rs:143:21
    |
 LL |     let _ = S2 { s: &*s };
-   |                      ^^ help: try this: `s`
+   |                     ^^^ help: try this: `&s`
 
 error: deref which would be done by auto-deref
-  --> $DIR/explicit_auto_deref.rs:156:30
+  --> $DIR/explicit_auto_deref.rs:159:30
    |
 LL |             let _ = Self::S1(&**s);
    |                              ^^^^ help: try this: `s`
 
 error: deref which would be done by auto-deref
-  --> $DIR/explicit_auto_deref.rs:157:35
+  --> $DIR/explicit_auto_deref.rs:160:35
    |
 LL |             let _ = Self::S2 { s: &**s };
    |                                   ^^^^ help: try this: `s`
 
 error: deref which would be done by auto-deref
-  --> $DIR/explicit_auto_deref.rs:160:21
+  --> $DIR/explicit_auto_deref.rs:163:20
    |
 LL |     let _ = E1::S1(&*s);
-   |                     ^^ help: try this: `s`
+   |                    ^^^ help: try this: `&s`
 
 error: deref which would be done by auto-deref
-  --> $DIR/explicit_auto_deref.rs:161:26
+  --> $DIR/explicit_auto_deref.rs:164:25
    |
 LL |     let _ = E1::S2 { s: &*s };
-   |                          ^^ help: try this: `s`
+   |                         ^^^ help: try this: `&s`
 
 error: deref which would be done by auto-deref
-  --> $DIR/explicit_auto_deref.rs:179:13
+  --> $DIR/explicit_auto_deref.rs:182:13
    |
 LL |     let _ = (*b).foo;
    |             ^^^^ help: try this: `b`
 
 error: deref which would be done by auto-deref
-  --> $DIR/explicit_auto_deref.rs:180:13
+  --> $DIR/explicit_auto_deref.rs:183:13
    |
 LL |     let _ = (**b).foo;
    |             ^^^^^ help: try this: `b`
 
 error: deref which would be done by auto-deref
-  --> $DIR/explicit_auto_deref.rs:195:19
+  --> $DIR/explicit_auto_deref.rs:198:19
    |
 LL |     let _ = f_str(*ref_str);
    |                   ^^^^^^^^ help: try this: `ref_str`
 
 error: deref which would be done by auto-deref
-  --> $DIR/explicit_auto_deref.rs:197:19
+  --> $DIR/explicit_auto_deref.rs:200:19
    |
 LL |     let _ = f_str(**ref_ref_str);
    |                   ^^^^^^^^^^^^^ help: try this: `ref_ref_str`
 
 error: deref which would be done by auto-deref
-  --> $DIR/explicit_auto_deref.rs:207:13
+  --> $DIR/explicit_auto_deref.rs:210:13
    |
 LL |     f_str(&&*ref_str); // `needless_borrow` will suggest removing both references
    |             ^^^^^^^^ help: try this: `ref_str`
 
 error: deref which would be done by auto-deref
-  --> $DIR/explicit_auto_deref.rs:208:12
+  --> $DIR/explicit_auto_deref.rs:211:12
    |
 LL |     f_str(&&**ref_str); // `needless_borrow` will suggest removing only one reference
    |            ^^^^^^^^^^ help: try this: `ref_str`
 
 error: deref which would be done by auto-deref
-  --> $DIR/explicit_auto_deref.rs:217:41
+  --> $DIR/explicit_auto_deref.rs:220:41
    |
 LL |     let _ = || -> &'static str { return *s };
    |                                         ^^ help: try this: `s`
 
-error: aborting due to 33 previous errors
+error: deref which would be done by auto-deref
+  --> $DIR/explicit_auto_deref.rs:239:9
+   |
+LL |         &**x
+   |         ^^^^ help: try this: `x`
+
+error: deref which would be done by auto-deref
+  --> $DIR/explicit_auto_deref.rs:262:8
+   |
+LL |     c1(*x);
+   |        ^^ help: try this: `x`
+
+error: deref which would be done by auto-deref
+  --> $DIR/explicit_auto_deref.rs:265:20
+   |
+LL |             return *x;
+   |                    ^^ help: try this: `x`
+
+error: deref which would be done by auto-deref
+  --> $DIR/explicit_auto_deref.rs:267:9
+   |
+LL |         *x
+   |         ^^ help: try this: `x`
+
+error: aborting due to 39 previous errors