# Nullish coalescing expression tests

- source: "null ?? 42"
  expected: 42
  description: "Left operand is null, returns right operand"

- source: "undefined ?? 42"
  expected: 42
  description: "Left operand is undefined, returns right operand"

- source: "0 ?? 42"
  expected: 0
  description: "Left operand is 0 (falsy but not nullish), returns left operand"

- source: "'' ?? 'default'"
  expected: ""
  description: "Left operand is an empty string (falsy but not nullish), returns left operand"

- source: "false ?? true"
  expected: false
  description: "Left operand is false (falsy but not nullish), returns left operand"

- source: "42 ?? 0"
  expected: 42
  description: "Left operand is a non-nullish truthy value, returns left operand"

- source: "null ?? undefined"
  expected: __undefined__
  description: "Left operand is null, returns right operand which is undefined"

- source: "undefined ?? null"
  expected: __null__
  description: "Left operand is undefined, returns right operand which is null"

- source: "NaN ?? 42"
  expected: __NaN__
  description: "Left operand is NaN (not nullish), returns left operand"

- source: "[] ?? 'default'"
  expected: []
  description: "Left operand is an empty array (not nullish), returns left operand"

- source: "{} ?? 'default'"
  expected: {}
  description: "Left operand is an empty object (not nullish), returns left operand"

- source: "(null ?? 42) ?? 50"
  expected: 42
  description: "Nested nullish coalescing, first nullish operand replaced, second ignored"

- source: "(undefined ?? null) ?? 'fallback'"
  expected: fallback
  description: "Nested nullish coalescing"

- source: "(0 ?? null) ?? 'fallback'"
  expected: 0
  description: "Nested nullish coalescing with falsy but non-nullish value"

- source: "null ?? (undefined ?? 42)"
  expected: 42
  description: "Nullish coalescing in the right operand"

- source: "null ?? null ?? null ?? 'fallback'"
  expected: "fallback"
  description: "Chained nullish coalescing, resolves to the last non-nullish value"

- source: "null ?? (false ?? 'default')"
  expected: false
  description: "Right operand evaluates to non-nullish falsy value"

- source: "null ?? (true ?? 'default')"
  expected: true
  description: "Right operand evaluates to truthy value"

- source: "42 ?? (null ?? 0)"
  expected: 42
  description: "Left operand is not nullish, ignores right operand"

- source: "undefined ?? null ?? 'value'"
  expected: "value"
  description: "Chained nullish coalescing with undefined and null"

- source: "(NaN ?? null) ?? 42"
  expected: __NaN__
  description: "Left operand is NaN, not nullish, returns NaN"

- source: "(undefined ?? NaN) ?? 42"
  expected: __NaN__
  description: "Right operand resolves to NaN"

- source: "null ?? 'default' ?? 42"
  expected: "default"
  description: "Chained nullish coalescing, resolves to first non-nullish value"

- source: "'' ?? 'default' ?? 42"
  expected: ""
  description: "Falsy but non-nullish value, returns left operand"

- source: "null ?? undefined ?? NaN"
  expected: __NaN__
  description: "Chained nullish coalescing, resolves to NaN as the first non-nullish value"

- source: "(null ?? null) ?? undefined"
  expected: __undefined__
  description: "Nested nullish coalescing resolves to undefined"