Address CR feedback

Author: ahejlsberg

src/compiler/checker.ts

@@ -7603,10 +7603,12 @@ namespace ts {
                         }
                         return;
                     }
-                    // Find each target constituent type that has an identically matching source
-                    // constituent type, and for each such target constituent type infer from the type to
-                    // itself. When inferring from a type to itself we effectively find all type parameter
-                    // occurrences within that type and infer themselves as their type arguments.
+                    // Find each source constituent type that has an identically matching target constituent
+                    // type, and for each such type infer from the type to itself. When inferring from a
+                    // type to itself we effectively find all type parameter occurrences within that type
+                    // and infer themselves as their type arguments. We have special handling for numeric
+                    // and string literals because the number and string types are not represented as unions
+                    // of all their possible values.
                     let matchingTypes: Type[];
                     for (const t of (<UnionOrIntersectionType>source).types) {
                         if (typeIdenticalToSomeType(t, (<UnionOrIntersectionType>target).types)) {
@@ -7616,8 +7618,7 @@ namespace ts {
                         else if (t.flags & (TypeFlags.NumberLiteral | TypeFlags.StringLiteral)) {
                             const b = getBaseTypeOfLiteralType(t);
                             if (typeIdenticalToSomeType(b, (<UnionOrIntersectionType>target).types)) {
-                                (matchingTypes || (matchingTypes = [])).push(t);
-                                matchingTypes.push(b);
+                                (matchingTypes || (matchingTypes = [])).push(t, b);
                             }
                         }
                     }