1 files changed, 115 insertions, 0 deletions

diff --git a/crates/ra_hir/src/diagnostics.rs b/crates/ra_hir/src/diagnostics.rs
new file mode 100644
index 000000000..d6a51b833
--- /dev/null
+++ b/crates/ra_hir/src/diagnostics.rs
@@ -0,0 +1,115 @@
+use std::{fmt, any::Any};
+
+use ra_syntax::{SyntaxNodePtr, TreeArc, AstPtr, TextRange, ast, SyntaxNode};
+use relative_path::RelativePathBuf;
+
+use crate::{HirFileId, HirDatabase};
+
+/// Diagnostic defines hir API for errors and warnings.
+///
+/// It is used as a `dyn` object, which you can downcast to a concrete
+/// diagnostic. DiagnosticSink are structured, meaning that they include rich
+/// information which can be used by IDE to create fixes. DiagnosticSink 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
+/// subsystem (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 message(&self) -> String;
+    fn file(&self) -> HirFileId;
+    fn syntax_node_ptr(&self) -> SyntaxNodePtr;
+    fn highlight_range(&self) -> TextRange {
+        self.syntax_node_ptr().range()
+    }
+    fn as_any(&self) -> &(dyn Any + Send + 'static);
+}
+
+impl dyn Diagnostic {
+    pub fn syntax_node(&self, db: &impl HirDatabase) -> TreeArc<SyntaxNode> {
+        let source_file = db.hir_parse(self.file());
+        self.syntax_node_ptr().to_node(&source_file).to_owned()
+    }
+    pub fn downcast_ref<D: Diagnostic>(&self) -> Option<&D> {
+        self.as_any().downcast_ref()
+    }
+}
+
+pub struct DiagnosticSink<'a> {
+    callbacks: Vec<Box<dyn FnMut(&dyn Diagnostic) -> Result<(), ()> + 'a>>,
+    default_callback: Box<dyn FnMut(&dyn Diagnostic) + 'a>,
+}
+
+impl<'a> DiagnosticSink<'a> {
+    pub fn new(cb: impl FnMut(&dyn Diagnostic) + 'a) -> DiagnosticSink<'a> {
+        DiagnosticSink { callbacks: Vec::new(), default_callback: Box::new(cb) }
+    }
+
+    pub fn on<D: Diagnostic, F: FnMut(&D) + 'a>(mut self, mut cb: F) -> DiagnosticSink<'a> {
+        let cb = move |diag: &dyn Diagnostic| match diag.downcast_ref::<D>() {
+            Some(d) => {
+                cb(d);
+                Ok(())
+            }
+            None => Err(()),
+        };
+        self.callbacks.push(Box::new(cb));
+        self
+    }
+
+    pub(crate) fn push(&mut self, d: impl Diagnostic) {
+        let d: &dyn Diagnostic = &d;
+        for cb in self.callbacks.iter_mut() {
+            match cb(d) {
+                Ok(()) => return,
+                Err(()) => (),
+            }
+        }
+        (self.default_callback)(d)
+    }
+}
+
+#[derive(Debug)]
+pub struct NoSuchField {
+    pub file: HirFileId,
+    pub field: AstPtr<ast::NamedField>,
+}
+
+impl Diagnostic for NoSuchField {
+    fn message(&self) -> String {
+        "no such field".to_string()
+    }
+    fn file(&self) -> HirFileId {
+        self.file
+    }
+    fn syntax_node_ptr(&self) -> SyntaxNodePtr {
+        self.field.into()
+    }
+    fn as_any(&self) -> &(Any + Send + 'static) {
+        self
+    }
+}
+
+#[derive(Debug)]
+pub struct UnresolvedModule {
+    pub file: HirFileId,
+    pub decl: AstPtr<ast::Module>,
+    pub candidate: RelativePathBuf,
+}
+
+impl Diagnostic for UnresolvedModule {
+    fn message(&self) -> String {
+        "unresolved module".to_string()
+    }
+    fn file(&self) -> HirFileId {
+        self.file
+    }
+    fn syntax_node_ptr(&self) -> SyntaxNodePtr {
+        self.decl.into()
+    }
+    fn as_any(&self) -> &(Any + Send + 'static) {
+        self
+    }
+}