parser:
./a%20b
./"a%20b"
text interpolation and escapes
remove `double`
remove imports/parenthesizeUsing
remove multilet
selection by expression unit tests
success/
    imports/
        Missing missing
        Headers https://example.com/foo using ./headers
        HeadersInteriorHash https://example.com/foo using (./headers sha256:0000000000000000000000000000000000000000000000000000000000000000)
        HeadersExteriorHash (https://example.com/foo using ./headers) sha256:0000000000000000000000000000000000000000000000000000000000000000
        HeadersHashPrecedence https://example.com/foo using ./headers sha256:0000000000000000000000000000000000000000000000000000000000000000
        HeadersDoubleHashPrecedence https://example.com/foo using ./headers sha256:0000000000000000000000000000000000000000000000000000000000000000 sha256:1111111111111111111111111111111111111111111111111111111111111111
    DoubleLitPositive 1.23
    DoubleLitNegative -1.23
    DoubleLitExponent 1.23e4
    DoubleLitExponentNoDot 1e4
    DoubleLitExponentNegative 1.23e-4
    DoubleLitInfinity Infinity
    DoubleLitNegInfinity -Infinity
    DoubleLitNaN NaN
    DoubleLitSecretelyInt 1.0
    DoubleLitZero 0.0
    BuiltinListBuild List/Build
    FunctionApplicationOneArg f x
    FunctionApplicationMultipleArgs f x y z
    Annotation x : T
    ListLitNonEmpty [x, y]
    ListLitNonEmptyAnnotated [x, y] : List T
    OptionalLitEmpty []: Optional T
    OptionalLitNonEmpty [x]: Optional T
    Field r.x
    FieldBuiltinName r.List
    FieldQuoted r.`x`
    Projection r.{x, y, z}
    Let let x: T = v in e
    LetNested let x: T = v in let y: U = w in e
    LetMulti let x: T = v let y: U = w in e
    LambdaUnicode λ(x : T) -> y
    FunctionTypePi forall(x: T) -> U
    FunctionTypePiUnicode ∀(x: T) -> U
    FunctionTypePiNested forall(x: T) -> ∀(y: U) -> V
    FunctionTypePiUnderscore forall(_: T) -> U
    FunctionTypeArrow T -> U
    RecordLit { x = 1, y = 2 }
    RecordType { x: T, y: U }
    operators/
        ImportAlt x ? y
        ImportAltAssoc w ? x ? y ? z
        BoolOr x || y
        BoolOrAssoc w || x || y || z
        NaturalPlus x + y
        NaturalPlusAssoc w + x + y + z
        TextAppend x ++ y
        TextAppendAssoc w ++ x ++ y ++ z
        ListAppend x # y
        ListAppendAssoc w # x # y # z
        BoolAnd x && y
        BoolAndAssoc w && x && y && z
        NaturalTimes x * y
        NaturalTimesAssoc w * x * y * z
        BoolEQ x == y
        BoolEQAssoc w == x == y == z
        BoolNE x != y
        BoolNEAssoc w != x != y != z
        RecursiveRecordMerge x //\\ y
        RecursiveRecordMergeAssoc w //\\ x //\\ y //\\ z
        RecursiveRecordTypeMerge x /\ y
        RecursiveRecordTypeMergeAssoc w /\ x /\ y /\ z
        RightBiasedRecordMerge x // y
        RightBiasedRecordMergeAssoc w // x // y // z
        RecursiveRecordMergeUnicode x ∧ y
        RecursiveRecordMergeUnicodeAssoc w ∧ x /\ y ∧ z
        RightBiasedRecordMergeUnicode x ⫽ y
        RightBiasedRecordMergeUnicodeAssoc w ⫽ x // y ⫽ z
        RecursiveRecordTypeMergeUnicode x ⩓ y
        RecursiveRecordTypeMergeUnicodeAssoc w ⩓ x //\\ y ⩓ z
        PrecedenceAll1 a ? b || c + d ++ e # f && g ∧ h ⫽ i ⩓ j * k == l != m n.o
        PrecedenceAll2 a b != c == d * e ⩓ f ⫽ g ∧ h && i # j ++ k + l || m ? n
        PrecedenceNat a + b * d + e f * (g + h)
        PrecedenceBool a && b || c d == e || f != g && h || i
        PrecedenceRecord a // b c /\ d ⫽ e.{x} ∧ f
failure/
    ProjectionByExpressionNeedsParens r.{ x: T }


import:
success/
    recover type error
    recover recursive import error
failure/
    don't recover cycle

normalization:
variables across import boundaries
    TextLitNested1 "${""}${x}"
    TextLitNested2 "${"${x}"}"
    TextLitNested3 "${"${""}"}${x}"
    EquivalenceDouble if b then NaN else NaN
    EquivalenceAlpha if b then \(x: T) -> x else \(y: T) -> y

typecheck:
something that involves destructuring a recordtype after merge
success/
    MergeEmptyAlternative merge { x = 1 } < x >.x
    MergeTrickyShadowing let _ = Bool in merge {_ = \(x: _) -> x} (<_: Bool>._ True)
    EquivalenceAlpha \(TODO: forall(x: Type) -> x) -> TODO : forall(y: Type) -> y
failure/
    MergeEmptyNeedsDirectAnnotation1 \(x: <>) -> (merge {=} x) : Bool
    MergeEmptyNeedsDirectAnnotation2 \(x: <>) -> let y: Bool = merge {=} x in 1
    MergeBoolIsNotUnion merge x True
    MergeOptionalIsNotUnion merge x (Some 1)
    MergeMissingHandler1 merge {=} < x >.x
    MergeMissingHandler2 merge {x=...,} <x|y>.x
    merge { x = λ(x : Bool) → x } (< x: Bool | y: Natural >.x True)
    merge { x = λ(_ : Bool) → _, y = 1 } < x = True | y >
    merge { x = True, y = 1 } < x | y >.x
    merge {x=...,y=...} <x>.x
    merge {x=...,y=...} <x:T>.x
    MergeHandlerFreeVar merge { x = None } < x = Bool >
    UnionTypeDuplicateVariants1 <x, x>
    UnionTypeDuplicateVariants2 <x, x:T>
    UnionLitDuplicateVariants <x=1|x:T>
    RecordLitDuplicateFields { x: T, x: T }
    EquivalenceAlphaTrap \(TODO: forall(_: Type) -> _) -> TODO : forall(x: Type) -> _

equivalence: