lint incoherent inherent impls

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

@@ -0,0 +1,77 @@
+use hir::InFile;
+
+use crate::{Diagnostic, DiagnosticsContext, Severity};
+
+// Diagnostic: incoherent-impl
+//
+// This diagnostic is triggered if the targe type of an impl is from a foreign crate.
+pub(crate) fn incoherent_impl(ctx: &DiagnosticsContext<'_>, d: &hir::IncoherentImpl) -> Diagnostic {
+    Diagnostic::new(
+        "incoherent-impl",
+        format!("cannot define inherent `impl` for foreign type"),
+        ctx.sema.diagnostics_display_range(InFile::new(d.file_id, d.impl_.clone().into())).range,
+    )
+    .severity(Severity::Error)
+}
+
+#[cfg(test)]
+mod change_case {
+    use crate::tests::check_diagnostics;
+
+    #[test]
+    fn primitive() {
+        check_diagnostics(
+            r#"
+  impl bool {}
+//^^^^^^^^^^^^ error: cannot define inherent `impl` for foreign type
+"#,
+        );
+    }
+
+    #[test]
+    fn primitive_rustc_allow_incoherent_impl() {
+        check_diagnostics(
+            r#"
+impl bool {
+    #[rustc_allow_incoherent_impl]
+    fn falsch(self) -> Self { false }
+}
+"#,
+        );
+    }
+
+    #[test]
+    fn rustc_allow_incoherent_impl() {
+        check_diagnostics(
+            r#"
+//- /lib.rs crate:foo
+#[rustc_has_incoherent_inherent_impls]
+pub struct S;
+//- /main.rs crate:main deps:foo
+impl foo::S {
+    #[rustc_allow_incoherent_impl]
+    fn func(self) {}
+}
+"#,
+        );
+        check_diagnostics(
+            r#"
+//- /lib.rs crate:foo
+pub struct S;
+//- /main.rs crate:main deps:foo
+  impl foo::S { #[rustc_allow_incoherent_impl] fn func(self) {} }
+//^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ error: cannot define inherent `impl` for foreign type
+"#,
+        );
+        check_diagnostics(
+            r#"
+//- /lib.rs crate:foo
+#[rustc_has_incoherent_inherent_impls]
+pub struct S;
+//- /main.rs crate:main deps:foo
+  impl foo::S { fn func(self) {} }
+//^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ error: cannot define inherent `impl` for foreign type
+"#,
+        );
+    }
+}