internal: document diagnostics crate

crates/ide_diagnostics/src/handlers/unresolved_import.rs

@@ -0,0 +1,90 @@
+use crate::{Diagnostic, DiagnosticsContext};
+
+// Diagnostic: unresolved-import
+//
+// This diagnostic is triggered if rust-analyzer is unable to resolve a path in
+// a `use` declaration.
+pub(crate) fn unresolved_import(
+    ctx: &DiagnosticsContext<'_>,
+    d: &hir::UnresolvedImport,
+) -> Diagnostic {
+    Diagnostic::new(
+        "unresolved-import",
+        "unresolved import",
+        ctx.sema.diagnostics_display_range(d.decl.clone().map(|it| it.into())).range,
+    )
+    // This currently results in false positives in the following cases:
+    // - `cfg_if!`-generated code in libstd (we don't load the sysroot correctly)
+    // - `core::arch` (we don't handle `#[path = "../<path>"]` correctly)
+    // - proc macros and/or proc macro generated code
+    .experimental()
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::tests::check_diagnostics;
+
+    #[test]
+    fn unresolved_import() {
+        check_diagnostics(
+            r#"
+use does_exist;
+use does_not_exist;
+  //^^^^^^^^^^^^^^ unresolved import
+
+mod does_exist {}
+"#,
+        );
+    }
+
+    #[test]
+    fn unresolved_import_in_use_tree() {
+        // Only the relevant part of a nested `use` item should be highlighted.
+        check_diagnostics(
+            r#"
+use does_exist::{Exists, DoesntExist};
+                       //^^^^^^^^^^^ unresolved import
+
+use {does_not_exist::*, does_exist};
+   //^^^^^^^^^^^^^^^^^ unresolved import
+
+use does_not_exist::{
+    a,
+  //^ unresolved import
+    b,
+  //^ unresolved import
+    c,
+  //^ unresolved import
+};
+
+mod does_exist {
+    pub struct Exists;
+}
+"#,
+        );
+    }
+
+    #[test]
+    fn dedup_unresolved_import_from_unresolved_crate() {
+        check_diagnostics(
+            r#"
+//- /main.rs crate:main
+mod a {
+    extern crate doesnotexist;
+  //^^^^^^^^^^^^^^^^^^^^^^^^^^ unresolved extern crate
+
+    // Should not error, since we already errored for the missing crate.
+    use doesnotexist::{self, bla, *};
+
+    use crate::doesnotexist;
+      //^^^^^^^^^^^^^^^^^^^ unresolved import
+}
+
+mod m {
+    use super::doesnotexist;
+      //^^^^^^^^^^^^^^^^^^^ unresolved import
+}
+"#,
+        );
+    }
+}