// Test let bindings.

---
// Automatically initialized with none.
#let x
#test(x, none)

// Manually initialized with one.
#let z = 1
#test(z, 1)

// Syntax sugar for function definitions.
#let fill = conifer
#let f(body) = rect(width: 2cm, fill: fill, inset: 5pt, body)
#f[Hi!]

---
// Termination.

// Terminated by line break.
#let v1 = 1
One

// Terminated by semicolon.
#let v2 = 2; Two

// Terminated by semicolon and line break.
#let v3 = 3;
Three

#test(v1, 1)
#test(v2, 2)
#test(v3, 3)

---
// Test parenthesised assignments.
// Ref: false
#let (a) = (1, 2)

---
// Ref: false
// Simple destructuring.
#let (a, b) = (1, 2)
#test(a, 1)
#test(b, 2)

---
// Ref: false
#let (a,) = (1,)
#test(a, 1)

---
// Ref: false
// Destructuring with multiple placeholders.
#let (a, _, c, _) = (1, 2, 3, 4)
#test(a, 1)
#test(c, 3)

---
// Ref: false
// Destructuring with a sink.
#let (a, b, ..c) = (1, 2, 3, 4, 5, 6)
#test(a, 1)
#test(b, 2)
#test(c, (3, 4, 5, 6))

---
// Ref: false
// Destructuring with a sink in the middle.
#let (a, ..b, c) = (1, 2, 3, 4, 5, 6)
#test(a, 1)
#test(b, (2, 3, 4, 5))
#test(c, 6)

---
// Ref: false
// Destructuring with an empty sink.
#let (..a, b, c) = (1, 2)
#test(a, ())
#test(b, 1)
#test(c, 2)

---
// Ref: false
// Destructuring with an empty sink.
#let (a, ..b, c) = (1, 2)
#test(a, 1)
#test(b, ())
#test(c, 2)

---
// Ref: false
// Destructuring with an empty sink.
#let (a, b, ..c) = (1, 2)
#test(a, 1)
#test(b, 2)
#test(c, ())

---
// Ref: false
// Destructuring with an empty sink and empty array.
#let (..a) = ()
#test(a, ())

---
// Ref: false
// Destructuring with unnamed sink.
#let (a, .., b) = (1, 2, 3, 4)
#test(a, 1)
#test(b, 4)

// Error: 10-11 at most one binding per identifier is allowed
#let (a, a) = (1, 2)

// Error: 12-15 at most one destructuring sink is allowed
#let (..a, ..a) = (1, 2)

// Error: 12-13 at most one binding per identifier is allowed
#let (a, ..a) = (1, 2)

// Error: 13-14 at most one binding per identifier is allowed
#let (a: a, a) = (a: 1, b: 2)

---
// Error: 13-14 not enough elements to destructure
#let (a, b, c) = (1, 2)

---
// Error: 6-20 not enough elements to destructure
#let (..a, b, c, d) = (1, 2)

---
// Error: 6-12 cannot destructure boolean
#let (a, b) = true

---
// Ref: false
// Simple destructuring.
#let (a: a, b, x: c) = (a: 1, b: 2, x: 3)
#test(a, 1)
#test(b, 2)
#test(c, 3)

---
// Ref: false
// Destructuring with a sink.
#let (a: _, ..b) = (a: 1, b: 2, c: 3)
#test(b, (b: 2, c: 3))

---
// Ref: false
// Destructuring with a sink in the middle.
#let (a: _, ..b, c: _) = (a: 1, b: 2, c: 3)
#test(b, (b: 2))

---
// Ref: false
// Destructuring with an empty sink.
#let (a: _, ..b) = (a: 1)
#test(b, (:))

---
// Ref: false
// Destructuring with an empty sink and empty dict.
#let (..a) = (:)
#test(a, (:))

---
// Ref: false
// Destructuring with unnamed sink.
#let (a, ..) = (a: 1, b: 2)
#test(a, 1)

---
// Error: 10-13 expected identifier, found string
// Error: 18-19 expected identifier, found integer
#let (a: "a", b: 2) = (a: 1, b: 2)

---
// Error: 10-11 destructuring key not found in dictionary
#let (a, b) = (a: 1)

---
// Error: 13-14 destructuring key not found in dictionary
#let (a, b: b) = (a: 1)

---
// Error: 7-8 cannot destructure named elements from an array
#let (a: a, b) = (1, 2, 3)

---
// Error: 5 expected identifier
#let

// Error: 6 expected identifier
#{let}

// Error: 5 expected identifier
// Error: 5 expected semicolon or line break
#let "v"

// Error: 7 expected semicolon or line break
#let v 1

// Error: 9 expected expression
#let v =

// Error: 5 expected identifier
// Error: 5 expected semicolon or line break
#let "v" = 1

// Terminated because expression ends.
// Error: 12 expected semicolon or line break
#let v4 = 4 Four

// Terminated by semicolon even though we are in a paren group.
// Error: 18 expected expression
// Error: 18 expected closing paren
#let v5 = (1, 2 + ; Five

// Error: 9-13 expected identifier, found boolean
#let (..true) = false

---
// Error: 13 expected equals sign
#let func(x)

// Error: 15 expected expression
#let func(x) =