1 files changed, 37 insertions, 8 deletions

diff --git a/crates/ra_hir/src/diagnostics.rs b/crates/ra_hir/src/diagnostics.rs
index 46a3fdd47..e8bb1ed92 100644
--- a/crates/ra_hir/src/diagnostics.rs
+++ b/crates/ra_hir/src/diagnostics.rs
@@ -3,7 +3,20 @@ use std::{fmt, any::Any};
 use ra_syntax::{SyntaxNodePtr, AstPtr, ast};
 
 use crate::HirFileId;
+use relative_path::RelativePathBuf;
 
+/// Diagnostic defines hir API for errors and warnings.
+///
+/// It is used as a `dyn` object, which you can downcast to a concrete
+/// diagnostic. Diagnostics are structured, meaning that they include rich
+/// information which can be used by IDE to create fixes. Diagnostics are
+/// expressed in terms of macro-expanded syntax tree nodes (so, it's a bad idea
+/// to diagnostic in a salsa value).
+///
+/// Internally, various subsystems of hir produce diagnostics specific to a
+/// subsytem (typically, an `enum`), which are safe to store in salsa but do not
+/// include source locations. Such internal diagnostic are transformed into an
+/// instance of `Diagnostic` on demand.
 pub trait Diagnostic: Any + Send + Sync + fmt::Debug + 'static {
     fn file(&self) -> HirFileId;
     fn syntax_node(&self) -> SyntaxNodePtr;
@@ -34,14 +47,8 @@ impl Diagnostics {
 
 #[derive(Debug)]
 pub struct NoSuchField {
-    pub(crate) file: HirFileId,
-    pub(crate) field: AstPtr<ast::NamedField>,
-}
-
-impl NoSuchField {
-    pub fn field(&self) -> AstPtr<ast::NamedField> {
-        self.field
-    }
+    pub file: HirFileId,
+    pub field: AstPtr<ast::NamedField>,
 }
 
 impl Diagnostic for NoSuchField {
@@ -58,3 +65,25 @@ impl Diagnostic for NoSuchField {
         self
     }
 }
+
+#[derive(Debug)]
+pub struct UnresolvedModule {
+    pub file: HirFileId,
+    pub decl: AstPtr<ast::Module>,
+    pub candidate: RelativePathBuf,
+}
+
+impl Diagnostic for UnresolvedModule {
+    fn file(&self) -> HirFileId {
+        self.file
+    }
+    fn syntax_node(&self) -> SyntaxNodePtr {
+        self.decl.into()
+    }
+    fn message(&self) -> String {
+        "unresolved module".to_string()
+    }
+    fn as_any(&self) -> &(Any + Send + 'static) {
+        self
+    }
+}