Report name resolution failures

README.md

@@ -21,6 +21,7 @@ Super fast incremental analysis! Scans `all-packages.nix` in less than 0.1s and
   - Syntax errors. 
     - Incomplete syntax errors are currently suppressed to avoid noisy outputs during typing.
   - [x] Hard semantic errors reported as parse errors by Nix, like duplicated keys in attrsets.
+  - [x] Undefiend names.
   - [x] Warnings of legacy syntax.
   - [x] Warnings of unnecessary syntax.
   - [x] Warnings of unused bindings, `with` and `rec`.

src/def/nameres.rs

@@ -1,5 +1,5 @@
 use super::{BindingKey, BindingValue, Bindings, DefDatabase, Expr, ExprId, Module, NameDefId};
-use crate::{builtin, FileId};
+use crate::{builtin, Diagnostic, DiagnosticKind, FileId};
 use la_arena::{Arena, ArenaMap, Idx};
 use smol_str::SmolStr;
 use std::collections::HashMap;
@@ -210,7 +210,8 @@ impl ScopeData {
 /// Name resolution of all references.
 #[derive(Default, Debug, Clone, PartialEq, Eq)]
 pub struct NameResolution {
-    resolve_map: HashMap<ExprId, ResolveResult>,
+    // `None` value for unresolved names.
+    resolve_map: HashMap<ExprId, Option<ResolveResult>>,
 }
 
 impl NameResolution {
@@ -222,7 +223,7 @@ impl NameResolution {
             .filter_map(|(e, kind)| {
                 match kind {
                     // Inherited attrs are also translated into Expr::References.
-                    Expr::Reference(name) => Some((e, scopes.resolve_name(e, name)?)),
+                    Expr::Reference(name) => Some((e, scopes.resolve_name(e, name))),
                     _ => None,
                 }
             })
@@ -231,11 +232,29 @@ impl NameResolution {
     }
 
     pub fn get(&self, expr: ExprId) -> Option<&ResolveResult> {
-        self.resolve_map.get(&expr)
+        self.resolve_map.get(&expr)?.as_ref()
     }
 
     pub fn iter(&self) -> impl Iterator<Item = (ExprId, &'_ ResolveResult)> + '_ {
-        self.resolve_map.iter().map(|(e, res)| (*e, res))
+        self.resolve_map
+            .iter()
+            .filter_map(|(e, res)| Some((*e, res.as_ref()?)))
+    }
+
+    pub fn to_diagnostics(
+        &self,
+        db: &dyn DefDatabase,
+        file_id: FileId,
+    ) -> impl Iterator<Item = Diagnostic> + '_ {
+        let source_map = db.source_map(file_id);
+        self.resolve_map
+            .iter()
+            .filter(|(_, res)| res.is_none())
+            .filter_map(move |(&e, _)| {
+                let ptr = source_map.expr_node(e)?;
+                let range = ptr.text_range();
+                Some(Diagnostic::new(range, DiagnosticKind::UndefinedName))
+            })
     }
 }
 

src/diagnostic.rs

@@ -23,6 +23,9 @@ pub enum DiagnosticKind {
     MergePlainRecAttrset,
     MergeRecAttrset,
 
+    // Name resolution.
+    UndefinedName,
+
     // Liveness.
     UnusedBinding,
     UnusedWith,
@@ -52,7 +55,9 @@ impl Diagnostic {
 
     pub fn severity(&self) -> Severity {
         match self.kind {
-            DiagnosticKind::InvalidDynamic | DiagnosticKind::DuplicatedKey => Severity::Error,
+            DiagnosticKind::InvalidDynamic
+            | DiagnosticKind::DuplicatedKey
+            | DiagnosticKind::UndefinedName => Severity::Error,
             DiagnosticKind::EmptyInherit
             | DiagnosticKind::EmptyLetIn
             | DiagnosticKind::LetAttrset
@@ -97,6 +102,8 @@ impl Diagnostic {
                 "Merging rec-attrset with other attrsets or attrpath. Merged values can unexpectedly reference each other remotely as in a single `rec { ... }`"
             }
 
+            DiagnosticKind::UndefinedName => "Undefined name",
+
             DiagnosticKind::UnusedBinding => "Unused binding",
             DiagnosticKind::UnusedWith => "Unused `with`",
             DiagnosticKind::UnusedRec => "Unused `rec`",

src/ide/diagnostics.rs

@@ -11,6 +11,9 @@ pub(crate) fn diagnostics(db: &dyn DefDatabase, file: FileId) -> Vec<Diagnostic>
     let module = db.module(file);
     diags.extend(module.diagnostics().iter().cloned());
 
+    // Name resolution.
+    diags.extend(db.name_resolution(file).to_diagnostics(db, file));
+
     // Liveness check.
     let liveness = db.liveness_check(file);
     diags.extend(liveness.to_diagnostics(db, file));
@@ -56,6 +59,16 @@ mod tests {
         );
     }
 
+    #[test]
+    fn name_resolution() {
+        check(
+            "a",
+            expect![[r#"
+                0..1: Undefined name
+            "#]],
+        );
+    }
+
     #[test]
     fn liveness() {
         check(