Merge commit 'd5e2a7aca5' into clippyup

tests/ui/unnecessary_struct_initialization.rs

@@ -0,0 +1,77 @@
+// run-rustfix
+
+#![allow(unused)]
+#![warn(clippy::unnecessary_struct_initialization)]
+
+struct S {
+    f: String,
+}
+
+#[derive(Clone, Copy)]
+struct T {
+    f: u32,
+}
+
+struct U {
+    f: u32,
+}
+
+impl Clone for U {
+    fn clone(&self) -> Self {
+        // Do not lint: `Self` does not implement `Copy`
+        Self { ..*self }
+    }
+}
+
+#[derive(Copy)]
+struct V {
+    f: u32,
+}
+
+impl Clone for V {
+    fn clone(&self) -> Self {
+        // Lint: `Self` implements `Copy`
+        Self { ..*self }
+    }
+}
+
+fn main() {
+    // Should lint: `a` would be consumed anyway
+    let a = S { f: String::from("foo") };
+    let mut b = S { ..a };
+
+    // Should lint: `b` would be consumed, and is mutable
+    let c = &mut S { ..b };
+
+    // Should not lint as `d` is not mutable
+    let d = S { f: String::from("foo") };
+    let e = &mut S { ..d };
+
+    // Should lint as `f` would be consumed anyway
+    let f = S { f: String::from("foo") };
+    let g = &S { ..f };
+
+    // Should lint: the result of an expression is mutable
+    let h = &mut S {
+        ..*Box::new(S { f: String::from("foo") })
+    };
+
+    // Should not lint: `m` would be both alive and borrowed
+    let m = T { f: 17 };
+    let n = &T { ..m };
+
+    // Should not lint: `m` should not be modified
+    let o = &mut T { ..m };
+    o.f = 32;
+    assert_eq!(m.f, 17);
+
+    // Should not lint: `m` should not be modified
+    let o = &mut T { ..m } as *mut T;
+    unsafe { &mut *o }.f = 32;
+    assert_eq!(m.f, 17);
+
+    // Should lint: the result of an expression is mutable and temporary
+    let p = &mut T {
+        ..*Box::new(T { f: 5 })
+    };
+}