Diagnose private field accesses

crates/ide-diagnostics/src/handlers/private_field.rs

@@ -0,0 +1,55 @@
+use crate::{Diagnostic, DiagnosticsContext};
+
+// Diagnostic: private-field
+//
+// This diagnostic is triggered if created structure does not have field provided in record.
+pub(crate) fn private_field(ctx: &DiagnosticsContext<'_>, d: &hir::PrivateField) -> Diagnostic {
+    // FIXME: add quickfix
+    Diagnostic::new(
+        "private-field",
+        format!(
+            "field `{}` of `{}` is private",
+            d.field.name(ctx.sema.db),
+            d.field.parent_def(ctx.sema.db).name(ctx.sema.db)
+        ),
+        ctx.sema.diagnostics_display_range(d.expr.clone().map(|it| it.into())).range,
+    )
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::tests::check_diagnostics;
+
+    #[test]
+    fn private_field() {
+        check_diagnostics(
+            r#"
+mod module { pub struct Struct { field: u32 } }
+fn main(s: module::Struct) {
+    s.field;
+  //^^^^^^^ error: field `field` of `Struct` is private
+}
+"#,
+        );
+    }
+
+    #[test]
+    fn private_but_shadowed_in_deref() {
+        check_diagnostics(
+            r#"
+//- minicore: deref
+mod module {
+    pub struct Struct { field: Inner }
+    pub struct Inner { pub field: u32 }
+    impl core::ops::Deref for Struct {
+        type Target = Inner;
+        fn deref(&self) -> &Inner { &self.field }
+    }
+}
+fn main(s: module::Struct) {
+    s.field;
+}
+"#,
+        );
+    }
+}