Merge pull request #49912 from microsoft/fix/47508

fix(47508): noUncheckedIndexedAccess with enums Type narrowed

tests/cases/compiler/noUncheckedIndexAccess.ts

@@ -0,0 +1,30 @@
+//@noUncheckedIndexedAccess: true
+//@strictNullChecks: true
+
+enum Meat {
+    Sausage,
+    Bacon
+  }
+  const sausage = Meat.Sausage
+  const valueSausage = Meat[sausage]
+
+  const bacon = Meat.Bacon
+  const valueBacon = Meat[bacon]
+
+  const union: Meat.Bacon | Meat.Sausage = Meat.Bacon
+  const valueUnion = Meat[union]
+
+  //Avoiding a false positive
+  const value = Meat[0]
+
+  const valueUndefined = "testing"
+  const value2 = Meat[valueUndefined]
+
+  enum A {
+    a, b, c
+  }
+  enum B {
+    x, y, z
+  }
+  
+  const value3 = A[B.x];