Diagnose unresolved field accesses

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

@@ -0,0 +1,134 @@
+use hir::{db::AstDatabase, HirDisplay, InFile};
+use ide_db::{
+    assists::{Assist, AssistId, AssistKind},
+    base_db::FileRange,
+    label::Label,
+    source_change::SourceChange,
+};
+use syntax::{ast, AstNode, AstPtr};
+use text_edit::TextEdit;
+
+use crate::{Diagnostic, DiagnosticsContext};
+
+// Diagnostic: unresolved-field
+//
+// This diagnostic is triggered if a field does not exist on a given type.
+pub(crate) fn unresolved_field(
+    ctx: &DiagnosticsContext<'_>,
+    d: &hir::UnresolvedField,
+) -> Diagnostic {
+    let method_suffix = if d.method_with_same_name_exists {
+        ", but a method with a similar name exists"
+    } else {
+        ""
+    };
+    Diagnostic::new(
+        "unresolved-field",
+        format!(
+            "no field `{}` on type `{}`{method_suffix}",
+            d.name,
+            d.receiver.display(ctx.sema.db)
+        ),
+        ctx.sema.diagnostics_display_range(d.expr.clone().map(|it| it.into())).range,
+    )
+    .with_fixes(fixes(ctx, d))
+}
+
+fn fixes(ctx: &DiagnosticsContext<'_>, d: &hir::UnresolvedField) -> Option<Vec<Assist>> {
+    if d.method_with_same_name_exists {
+        method_fix(ctx, &d.expr)
+    } else {
+        // FIXME: add quickfix
+
+        None
+    }
+}
+
+// FIXME: We should fill out the call here, mvoe the cursor and trigger signature help
+fn method_fix(
+    ctx: &DiagnosticsContext<'_>,
+    expr_ptr: &InFile<AstPtr<ast::Expr>>,
+) -> Option<Vec<Assist>> {
+    let root = ctx.sema.db.parse_or_expand(expr_ptr.file_id)?;
+    let expr = expr_ptr.value.to_node(&root);
+    let FileRange { range, file_id } = ctx.sema.original_range_opt(expr.syntax())?;
+    Some(vec![Assist {
+        id: AssistId("expected-field-found-method-call-fix", AssistKind::QuickFix),
+        label: Label::new("Use parentheses to call the method".to_string()),
+        group: None,
+        target: range,
+        source_change: Some(SourceChange::from_text_edit(
+            file_id,
+            TextEdit::insert(range.end(), "()".to_owned()),
+        )),
+        trigger_signature_help: false,
+    }])
+}
+#[cfg(test)]
+mod tests {
+    use crate::tests::check_diagnostics;
+
+    #[test]
+    fn smoke_test() {
+        check_diagnostics(
+            r#"
+fn main() {
+    ().foo;
+ // ^^^^^^ error: no field `foo` on type `()`
+}
+"#,
+        );
+    }
+
+    #[test]
+    fn method_clash() {
+        check_diagnostics(
+            r#"
+struct Foo;
+impl Foo {
+    fn bar(&self) {}
+}
+fn foo() {
+    Foo.bar;
+ // ^^^^^^^ 💡 error: no field `bar` on type `Foo`, but a method with a similar name exists
+}
+"#,
+        );
+    }
+
+    #[test]
+    fn method_trait_() {
+        check_diagnostics(
+            r#"
+struct Foo;
+trait Bar {
+    fn bar(&self) {}
+}
+impl Bar for Foo {}
+fn foo() {
+    Foo.bar;
+ // ^^^^^^^ 💡 error: no field `bar` on type `Foo`, but a method with a similar name exists
+}
+"#,
+        );
+    }
+
+    #[test]
+    fn method_trait_2() {
+        check_diagnostics(
+            r#"
+struct Foo;
+trait Bar {
+    fn bar(&self);
+}
+impl Bar for Foo {
+    fn bar(&self) {}
+}
+fn foo() {
+    Foo.bar;
+ // ^^^^^^^ 💡 error: no field `bar` on type `Foo`, but a method with a similar name exists
+}
+"#,
+        );
+    }
+}