Auto merge of #3744 - phansch:fix3144, r=oli-obk

Fix ICE in needless_pass_by_value lint

If I understand it correctly, we were first creating a type with a
`RegionKind::ReErased` region and then deleted it again in
`util::implements_trait` with:

    cx.tcx.erase_regions(&ty);

causing the type query to fail.

It looks like using `ReEmpty` works around that deletion.

Fixes #3144

Author: bors

clippy_lints/src/needless_pass_by_value.rs

@@ -193,7 +193,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for NeedlessPassByValue {
                                 .skip(1)
                                 .cloned()
                                 .collect::<Vec<_>>();
-                            implements_trait(cx, cx.tcx.mk_imm_ref(&RegionKind::ReErased, ty), t.def_id(), ty_params)
+                            implements_trait(cx, cx.tcx.mk_imm_ref(&RegionKind::ReEmpty, ty), t.def_id(), ty_params)
                         }),
                 )
             };

tests/ui/needless_pass_by_value.rs

@@ -8,6 +8,7 @@
 )]
 
 use std::borrow::Borrow;
+use std::collections::HashSet;
 use std::convert::AsRef;
 
 // `v` should be warned
@@ -145,4 +146,14 @@ trait Club<'a, A> {}
 impl<T> Club<'static, T> for T {}
 fn more_fun(_item: impl Club<'static, i32>) {}
 
-fn main() {}
+fn is_sync<T>(_: T)
+where
+    T: Sync,
+{
+}
+
+fn main() {
+    // This should not cause an ICE either
+    // https://github.com/rust-lang/rust-clippy/issues/3144
+    is_sync(HashSet::<usize>::new());
+}

tests/ui/needless_pass_by_value.stderr

@@ -1,31 +1,31 @@
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:15:23
+  --> $DIR/needless_pass_by_value.rs:16:23
    |
 LL | fn foo<T: Default>(v: Vec<T>, w: Vec<T>, mut x: Vec<T>, y: Vec<T>) -> Vec<T> {
    |                       ^^^^^^ help: consider changing the type to: `&[T]`
    |
    = note: `-D clippy::needless-pass-by-value` implied by `-D warnings`
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:29:11
+  --> $DIR/needless_pass_by_value.rs:30:11
    |
 LL | fn bar(x: String, y: Wrapper) {
    |           ^^^^^^ help: consider changing the type to: `&str`
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:29:22
+  --> $DIR/needless_pass_by_value.rs:30:22
    |
 LL | fn bar(x: String, y: Wrapper) {
    |                      ^^^^^^^ help: consider taking a reference instead: `&Wrapper`
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:35:71
+  --> $DIR/needless_pass_by_value.rs:36:71
    |
 LL | fn test_borrow_trait<T: Borrow<str>, U: AsRef<str>, V>(t: T, u: U, v: V) {
    |                                                                       ^ help: consider taking a reference instead: `&V`
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:47:18
+  --> $DIR/needless_pass_by_value.rs:48:18
    |
 LL | fn test_match(x: Option<Option<String>>, y: Option<Option<String>>) {
    |                  ^^^^^^^^^^^^^^^^^^^^^^
@@ -36,13 +36,13 @@ LL |     match *x {
    |
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:60:24
+  --> $DIR/needless_pass_by_value.rs:61:24
    |
 LL | fn test_destructure(x: Wrapper, y: Wrapper, z: Wrapper) {
    |                        ^^^^^^^ help: consider taking a reference instead: `&Wrapper`
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:60:36
+  --> $DIR/needless_pass_by_value.rs:61:36
    |
 LL | fn test_destructure(x: Wrapper, y: Wrapper, z: Wrapper) {
    |                                    ^^^^^^^
@@ -55,19 +55,19 @@ LL |     let Wrapper(_) = *y; // still not moved
    |
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:76:49
+  --> $DIR/needless_pass_by_value.rs:77:49
    |
 LL | fn test_blanket_ref<T: Foo, S: Serialize>(_foo: T, _serializable: S) {}
    |                                                 ^ help: consider taking a reference instead: `&T`
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:78:18
+  --> $DIR/needless_pass_by_value.rs:79:18
    |
 LL | fn issue_2114(s: String, t: String, u: Vec<i32>, v: Vec<i32>) {
    |                  ^^^^^^ help: consider taking a reference instead: `&String`
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:78:29
+  --> $DIR/needless_pass_by_value.rs:79:29
    |
 LL | fn issue_2114(s: String, t: String, u: Vec<i32>, v: Vec<i32>) {
    |                             ^^^^^^
@@ -81,13 +81,13 @@ LL |     let _ = t.to_string();
    |             ^^^^^^^^^^^^^
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:78:40
+  --> $DIR/needless_pass_by_value.rs:79:40
    |
 LL | fn issue_2114(s: String, t: String, u: Vec<i32>, v: Vec<i32>) {
    |                                        ^^^^^^^^ help: consider taking a reference instead: `&Vec<i32>`
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:78:53
+  --> $DIR/needless_pass_by_value.rs:79:53
    |
 LL | fn issue_2114(s: String, t: String, u: Vec<i32>, v: Vec<i32>) {
    |                                                     ^^^^^^^^
@@ -101,61 +101,61 @@ LL |     let _ = v.to_owned();
    |             ^^^^^^^^^^^^
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:91:12
+  --> $DIR/needless_pass_by_value.rs:92:12
    |
 LL |         s: String,
    |            ^^^^^^ help: consider changing the type to: `&str`
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:92:12
+  --> $DIR/needless_pass_by_value.rs:93:12
    |
 LL |         t: String,
    |            ^^^^^^ help: consider taking a reference instead: `&String`
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:101:23
+  --> $DIR/needless_pass_by_value.rs:102:23
    |
 LL |     fn baz(&self, _u: U, _s: Self) {}
    |                       ^ help: consider taking a reference instead: `&U`
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:101:30
+  --> $DIR/needless_pass_by_value.rs:102:30
    |
 LL |     fn baz(&self, _u: U, _s: Self) {}
    |                              ^^^^ help: consider taking a reference instead: `&Self`
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:123:24
+  --> $DIR/needless_pass_by_value.rs:124:24
    |
 LL | fn bar_copy(x: u32, y: CopyWrapper) {
    |                        ^^^^^^^^^^^ help: consider taking a reference instead: `&CopyWrapper`
    |
 help: consider marking this type as Copy
-  --> $DIR/needless_pass_by_value.rs:121:1
+  --> $DIR/needless_pass_by_value.rs:122:1
    |
 LL | struct CopyWrapper(u32);
    | ^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:129:29
+  --> $DIR/needless_pass_by_value.rs:130:29
    |
 LL | fn test_destructure_copy(x: CopyWrapper, y: CopyWrapper, z: CopyWrapper) {
    |                             ^^^^^^^^^^^ help: consider taking a reference instead: `&CopyWrapper`
    |
 help: consider marking this type as Copy
-  --> $DIR/needless_pass_by_value.rs:121:1
+  --> $DIR/needless_pass_by_value.rs:122:1
    |
 LL | struct CopyWrapper(u32);
    | ^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:129:45
+  --> $DIR/needless_pass_by_value.rs:130:45
    |
 LL | fn test_destructure_copy(x: CopyWrapper, y: CopyWrapper, z: CopyWrapper) {
    |                                             ^^^^^^^^^^^
    |
 help: consider marking this type as Copy
-  --> $DIR/needless_pass_by_value.rs:121:1
+  --> $DIR/needless_pass_by_value.rs:122:1
    |
 LL | struct CopyWrapper(u32);
    | ^^^^^^^^^^^^^^^^^^^^^^^^
@@ -168,13 +168,13 @@ LL |     let CopyWrapper(_) = *y; // still not moved
    |
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:129:61
+  --> $DIR/needless_pass_by_value.rs:130:61
    |
 LL | fn test_destructure_copy(x: CopyWrapper, y: CopyWrapper, z: CopyWrapper) {
    |                                                             ^^^^^^^^^^^
    |
 help: consider marking this type as Copy
-  --> $DIR/needless_pass_by_value.rs:121:1
+  --> $DIR/needless_pass_by_value.rs:122:1
    |
 LL | struct CopyWrapper(u32);
    | ^^^^^^^^^^^^^^^^^^^^^^^^
@@ -185,13 +185,13 @@ LL |     let CopyWrapper(s) = *z; // moved
    |
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:141:40
+  --> $DIR/needless_pass_by_value.rs:142:40
    |
 LL | fn some_fun<'b, S: Bar<'b, ()>>(_item: S) {}
    |                                        ^ help: consider taking a reference instead: `&S`
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:146:20
+  --> $DIR/needless_pass_by_value.rs:147:20
    |
 LL | fn more_fun(_item: impl Club<'static, i32>) {}
    |                    ^^^^^^^^^^^^^^^^^^^^^^^ help: consider taking a reference instead: `&impl Club<'static, i32>`