Merge pull request #19354 from ChayimFriedman2/rtn-prep

Preparation to Return Type Notation (RTN)

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

@@ -0,0 +1,52 @@
+use ide_db::Severity;
+
+use crate::{Diagnostic, DiagnosticCode, DiagnosticsContext};
+
+// Diagnostic: bad-rtn
+//
+// This diagnostic is shown when a RTN (Return Type Notation, `Type::method(..): Send`) is written in an improper place.
+pub(crate) fn bad_rtn(ctx: &DiagnosticsContext<'_>, d: &hir::BadRtn) -> Diagnostic {
+    Diagnostic::new_with_syntax_node_ptr(
+        ctx,
+        DiagnosticCode::Ra("bad-rtn", Severity::Error),
+        "return type notation not allowed in this position yet",
+        d.rtn.map(Into::into),
+    )
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::tests::check_diagnostics;
+
+    #[test]
+    fn fn_traits_also_emit() {
+        check_diagnostics(
+            r#"
+//- minicore: fn
+fn foo<
+    A: Fn(..),
+      // ^^^^ error: return type notation not allowed in this position yet
+>() {}
+        "#,
+        );
+    }
+
+    #[test]
+    fn bad_rtn() {
+        check_diagnostics(
+            r#"
+mod module {
+    pub struct Type;
+}
+trait Trait {}
+
+fn foo()
+where
+    module(..)::Type: Trait
+       // ^^^^ error: return type notation not allowed in this position yet
+{
+}
+        "#,
+        );
+    }
+}