handle non local non-exhaustive structs as well as private fields

Author: Erk-

clippy_lints/src/rest_when_destructuring_struct.rs

@@ -3,7 +3,7 @@ use clippy_utils::is_from_proc_macro;
 use itertools::Itertools;
 use rustc_abi::VariantIdx;
 use rustc_lint::LateLintPass;
-use rustc_middle::ty;
+use rustc_middle::ty::{self, Visibility};
 use rustc_session::declare_lint_pass;
 
 declare_clippy_lint! {
@@ -56,13 +56,33 @@ impl<'tcx> LateLintPass<'tcx> for RestWhenDestructuringStruct {
             let vid = qty
                 .opt_def_id()
                 .map_or(VariantIdx::ZERO, |x| a.variant_index_with_id(x));
+
+            let leave_dotdot = a.variants()[vid].field_list_has_applicable_non_exhaustive();
+
             let mut rest_fields = a.variants()[vid]
                 .fields
                 .iter()
+                .filter(|f| {
+                    if a.did().is_local() {
+                        true
+                    } else {
+                        matches!(f.vis, Visibility::Public)
+                    }
+                })
                 .map(|field| field.ident(cx.tcx))
                 .filter(|pf| !fields.iter().any(|x| x.ident == *pf))
                 .map(|x| format!("{x}: _"));
-            let fmt_fields = rest_fields.join(", ");
+
+            let mut fmt_fields = rest_fields.join(", ");
+
+            if fmt_fields.is_empty() && leave_dotdot {
+                // The struct is non_exhaustive, from a non-local crate and all public fields are explicitly named.
+                return;
+            }
+
+            if leave_dotdot {
+                fmt_fields.push_str(", ..");
+            }
 
             span_lint_and_then(
                 cx,

tests/ui/auxiliary/non-exhaustive-struct.rs

@@ -0,0 +1,7 @@
+#[non_exhaustive]
+#[derive(Default)]
+pub struct NonExhaustiveStruct {
+    pub field1: i32,
+    pub field2: i32,
+    _private: i32,
+}

tests/ui/rest_when_destructuring_struct.fixed

@@ -1,10 +1,15 @@
 //@aux-build:proc_macros.rs
+//@aux-build:non-exhaustive-struct.rs
 #![warn(clippy::rest_when_destructuring_struct)]
 #![allow(dead_code)]
 #![allow(unused_variables)]
 
 extern crate proc_macros;
 
+extern crate non_exhaustive_struct;
+
+use non_exhaustive_struct::NonExhaustiveStruct;
+
 struct S {
     a: u8,
     b: u8,
@@ -53,4 +58,13 @@ fn main() {
         let s2 = S { a: 1, b: 2, c: 3 };
         let S { a, b, .. } = s2;
     }
+
+    let ne = NonExhaustiveStruct::default();
+    let NonExhaustiveStruct { field1: _, field2: _, .. } = ne;
+    //~^ rest_when_destructuring_struct
+
+    let ne = NonExhaustiveStruct::default();
+    let NonExhaustiveStruct {
+        field1: _, field2: _, ..
+    } = ne;
 }

tests/ui/rest_when_destructuring_struct.rs

@@ -1,10 +1,15 @@
 //@aux-build:proc_macros.rs
+//@aux-build:non-exhaustive-struct.rs
 #![warn(clippy::rest_when_destructuring_struct)]
 #![allow(dead_code)]
 #![allow(unused_variables)]
 
 extern crate proc_macros;
 
+extern crate non_exhaustive_struct;
+
+use non_exhaustive_struct::NonExhaustiveStruct;
+
 struct S {
     a: u8,
     b: u8,
@@ -53,4 +58,13 @@ fn main() {
         let s2 = S { a: 1, b: 2, c: 3 };
         let S { a, b, .. } = s2;
     }
+
+    let ne = NonExhaustiveStruct::default();
+    let NonExhaustiveStruct { field1: _, .. } = ne;
+    //~^ rest_when_destructuring_struct
+
+    let ne = NonExhaustiveStruct::default();
+    let NonExhaustiveStruct {
+        field1: _, field2: _, ..
+    } = ne;
 }

tests/ui/rest_when_destructuring_struct.stderr

@@ -1,5 +1,5 @@
 error: struct destructuring with rest (..)
-  --> tests/ui/rest_when_destructuring_struct.rs:23:9
+  --> tests/ui/rest_when_destructuring_struct.rs:28:9
    |
 LL |     let S { a, b, .. } = s;
    |         ^^^^^^^^^^^^^^
@@ -13,7 +13,7 @@ LL +     let S { a, b, c: _ } = s;
    |
 
 error: struct destructuring with rest (..)
-  --> tests/ui/rest_when_destructuring_struct.rs:26:9
+  --> tests/ui/rest_when_destructuring_struct.rs:31:9
    |
 LL |     let S { a, b, c, .. } = s;
    |         ^^^^^^^^^^^^^^^^^
@@ -25,7 +25,7 @@ LL +     let S { a, b, c,  } = s;
    |
 
 error: struct destructuring with rest (..)
-  --> tests/ui/rest_when_destructuring_struct.rs:33:9
+  --> tests/ui/rest_when_destructuring_struct.rs:38:9
    |
 LL |         E::B { .. } => (),
    |         ^^^^^^^^^^^
@@ -37,7 +37,7 @@ LL +         E::B { b1: _, b2: _ } => (),
    |
 
 error: struct destructuring with rest (..)
-  --> tests/ui/rest_when_destructuring_struct.rs:35:9
+  --> tests/ui/rest_when_destructuring_struct.rs:40:9
    |
 LL |         E::C { .. } => (),
    |         ^^^^^^^^^^^
@@ -49,7 +49,7 @@ LL +         E::C {  } => (),
    |
 
 error: struct destructuring with rest (..)
-  --> tests/ui/rest_when_destructuring_struct.rs:41:9
+  --> tests/ui/rest_when_destructuring_struct.rs:46:9
    |
 LL |         E::B { b1: _, .. } => (),
    |         ^^^^^^^^^^^^^^^^^^
@@ -60,5 +60,16 @@ LL -         E::B { b1: _, .. } => (),
 LL +         E::B { b1: _, b2: _ } => (),
    |
 
-error: aborting due to 5 previous errors
+error: struct destructuring with rest (..)
+  --> tests/ui/rest_when_destructuring_struct.rs:63:9
+   |
+LL |     let NonExhaustiveStruct { field1: _, .. } = ne;
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: consider explicitly ignoring remaining fields with wildcard patterns (x: _)
+   |
+LL |     let NonExhaustiveStruct { field1: _, field2: _, .. } = ne;
+   |                                          ++++++++++
+
+error: aborting due to 6 previous errors