tests: add tests for mismatches with unresolved projections

crates/hir-ty/src/tests/diagnostics.rs

@@ -136,3 +136,20 @@ impl Trait for () {
 "#,
     );
 }
+
+#[test]
+fn no_mismatches_with_unresolved_projections() {
+    check_no_mismatches(
+        r#"
+// Thing is {unknown}
+fn create() -> Option<(i32, Thing)> {
+    Some((69420, Thing))
+}
+
+fn consume() -> Option<()> {
+    let (number, thing) = create()?;
+    Some(())
+}
+"#,
+    );
+}

crates/hir/src/lib.rs

@@ -73,7 +73,8 @@ use hir_ty::{
     traits::FnTrait,
     AliasTy, CallableDefId, CallableSig, Canonical, CanonicalVarKinds, Cast, ClosureId, GenericArg,
     GenericArgData, Interner, ParamKind, QuantifiedWhereClause, Scalar, Substitution,
-    TraitEnvironment, TraitRefExt, Ty, TyBuilder, TyDefId, TyExt, TyKind, ValueTyDefId, WhereClause,
+    TraitEnvironment, TraitRefExt, Ty, TyBuilder, TyDefId, TyExt, TyKind, ValueTyDefId,
+    WhereClause,
 };
 use itertools::Itertools;
 use nameres::diagnostics::DefDiagnosticKind;