Add test

Author: ahejlsberg

tests/cases/compiler/bestChoiceType.ts

@@ -0,0 +1,19 @@
+// @strictNullChecks: true
+
+// Repro from #10041
+
+(''.match(/ /) || []).map(s => s.toLowerCase());
+
+// Similar cases
+
+function f1() {
+    let x = ''.match(/ /);
+    let y = x || [];
+    let z = y.map(s => s.toLowerCase());
+}
+
+function f2() {
+    let x = ''.match(/ /);
+    let y = x ? x : [];
+    let z = y.map(s => s.toLowerCase());
+}