TPreferedDesc = enum
  preferName, preferDesc, preferExported, preferModuleInfo, preferGenericArg,
  preferTypeName, preferResolved, preferMixed

TTypeIter = proc (t: PType; closure: RootRef): bool {...}{.nimcall.}

TTypeMutator = proc (t: PType; closure: RootRef): PType {...}{.nimcall.}

TTypePredicate = proc (t: PType): bool {...}{.nimcall.}

TParamsEquality = enum
  paramsNotEqual, paramsEqual, paramsIncompatible

TTypeFieldResult = enum
  frNone, frHeader, frEmbedded

TDistinctCompare = enum
  dcEq,                     ## a and b should be the same type
  dcEqIgnoreDistinct,       ## compare symmetrically: (distinct a) == b, a == b
                             ## or a == (distinct b)
  dcEqOrDistinctOf           ## a equals b or a is distinct of b

TTypeCmpFlag = enum
  IgnoreTupleFields,        ## NOTE: Only set this flag for backends!
  IgnoreCC, ExactTypeDescValues, ExactGenericParams, ExactConstraints,
  ExactGcSafety, AllowCommonBase

TTypeCmpFlags = set[TTypeCmpFlag]

EffectsCompat = enum
  efCompat, efRaisesDiffer, efRaisesUnknown, efTagsDiffer, efTagsUnknown,
  efLockLevelsDiffer

OrdinalType = enum
  NoneLike, IntLike, FloatLike

abstractPtrs = {tyVar, tyPtr, tyRef, tyGenericInst, tyDistinct, tyOrdinal,
                tyTypeDesc, tyAlias, tyInferred, tySink, tyLent, tyOwned}

abstractVar = {tyVar, tyGenericInst, tyDistinct, tyOrdinal, tyTypeDesc, tyAlias,
               tyInferred, tySink, tyLent, tyOwned}

abstractRange = {tyGenericInst, tyRange, tyDistinct, tyOrdinal, tyTypeDesc,
                 tyAlias, tyInferred, tySink, tyOwned}

abstractInst = {tyGenericInst, tyDistinct, tyOrdinal, tyTypeDesc, tyAlias,
                tyInferred, tySink, tyOwned}

abstractInstOwned = {tyAlias, tyTypeDesc, tyGenericInst, tyDistinct, tyOrdinal,
                     tyOwned..tySink, tyInferred}

skipPtrs = {tyVar, tyPtr, tyRef, tyGenericInst, tyTypeDesc, tyAlias, tyInferred,
            tySink, tyLent, tyOwned}

typedescPtrs = {tyAlias, tyTypeDesc, tyGenericInst, tyDistinct, tyOrdinal,
                tyPtr..tyVar, tyOwned..tyLent, tyInferred}

typedescInst = {tyAlias, tyTypeDesc, tyGenericInst, tyDistinct, tyOrdinal,
                tyOwned..tySink, tyUserTypeClass, tyInferred}

szUnknownSize = -3

szIllegalRecursion = -2

szUncomputedSize = -1

szTooBigSize = -4

proc base(t: PType): PType {...}{.raises: [], tags: [].}

proc invalidGenericInst(f: PType): bool {...}{.raises: [], tags: [].}

proc isPureObject(typ: PType): bool {...}{.raises: [], tags: [].}

proc isUnsigned(t: PType): bool {...}{.raises: [], tags: [].}

proc getOrdValue(n: PNode; onError = high(Int128)): Int128 {...}{.raises: [],
    tags: [].}

proc getFloatValue(n: PNode): BiggestFloat {...}{.raises: [], tags: [].}

proc isIntLit(t: PType): bool {...}{.inline, raises: [], tags: [].}

proc isFloatLit(t: PType): bool {...}{.inline, raises: [], tags: [].}

proc addTypeHeader(result: var string; conf: ConfigRef; typ: PType;
                   prefer: TPreferedDesc = preferMixed;
                   getDeclarationPath = true) {...}{.raises: [Exception],
    tags: [RootEffect].}

proc getProcHeader(conf: ConfigRef; sym: PSym;
                   prefer: TPreferedDesc = preferName; getDeclarationPath = true): string {...}{.
    raises: [Exception], tags: [RootEffect].}

proc elemType(t: PType): PType {...}{.raises: [], tags: [].}

proc enumHasHoles(t: PType): bool {...}{.raises: [], tags: [].}

proc isOrdinalType(t: PType; allowEnumWithHoles: bool = false): bool {...}{.
    raises: [], tags: [].}

proc iterOverType(t: PType; iter: TTypeIter; closure: RootRef): bool {...}{.
    raises: [Exception], tags: [RootEffect].}

proc searchTypeFor(t: PType; predicate: TTypePredicate): bool {...}{.
    raises: [Exception], tags: [RootEffect].}

proc containsObject(t: PType): bool {...}{.raises: [Exception], tags: [RootEffect].}

proc analyseObjectWithTypeField(t: PType): TTypeFieldResult {...}{.
    raises: [Exception], tags: [RootEffect].}

proc containsGarbageCollectedRef(typ: PType): bool {...}{.raises: [Exception],
    tags: [RootEffect].}

proc containsManagedMemory(typ: PType): bool {...}{.raises: [Exception],
    tags: [RootEffect].}

proc containsTyRef(typ: PType): bool {...}{.raises: [Exception], tags: [RootEffect].}

proc containsHiddenPointer(typ: PType): bool {...}{.raises: [Exception],
    tags: [RootEffect].}

proc isFinal(t: PType): bool {...}{.raises: [], tags: [].}

proc canFormAcycle(typ: PType): bool {...}{.raises: [Exception], tags: [RootEffect].}

proc mutateType(t: PType; iter: TTypeMutator; closure: RootRef): PType {...}{.
    raises: [Exception], tags: [RootEffect].}

proc typeToString(typ: PType; prefer: TPreferedDesc = preferName): string {...}{.
    raises: [Exception, ValueError], tags: [RootEffect].}

proc firstOrd(conf: ConfigRef; t: PType): Int128 {...}{.
    raises: [Exception, ValueError, IOError, ERecoverableError],
    tags: [RootEffect, WriteIOEffect, ReadIOEffect, ReadEnvEffect].}

proc firstFloat(t: PType): BiggestFloat {...}{.
    raises: [Exception, ValueError, IOError, ERecoverableError],
    tags: [RootEffect, WriteIOEffect, ReadIOEffect, ReadEnvEffect].}

proc lastOrd(conf: ConfigRef; t: PType): Int128 {...}{.
    raises: [Exception, ValueError, IOError, ERecoverableError],
    tags: [RootEffect, WriteIOEffect, ReadIOEffect, ReadEnvEffect].}

proc lastFloat(t: PType): BiggestFloat {...}{.
    raises: [Exception, ValueError, IOError, ERecoverableError],
    tags: [RootEffect, WriteIOEffect, ReadIOEffect, ReadEnvEffect].}

proc floatRangeCheck(x: BiggestFloat; t: PType): bool {...}{.
    raises: [Exception, ValueError, IOError, ERecoverableError],
    tags: [RootEffect, WriteIOEffect, ReadIOEffect, ReadEnvEffect].}

proc lengthOrd(conf: ConfigRef; t: PType): Int128 {...}{.
    raises: [Exception, ValueError, IOError, ERecoverableError],
    tags: [RootEffect, WriteIOEffect, ReadIOEffect, ReadEnvEffect].}

proc sameType(a, b: PType; flags: TTypeCmpFlags = {}): bool {...}{.
    raises: [Exception], tags: [RootEffect].}

proc sameTypeOrNil(a, b: PType; flags: TTypeCmpFlags = {}): bool {...}{.
    raises: [Exception], tags: [RootEffect].}

proc equalParams(a, b: PNode): TParamsEquality {...}{.raises: [Exception],
    tags: [RootEffect].}

proc sameObjectTypes(a, b: PType): bool {...}{.raises: [Exception],
    tags: [RootEffect].}

proc sameDistinctTypes(a, b: PType): bool {...}{.inline, raises: [Exception],
    tags: [RootEffect].}

proc sameEnumTypes(a, b: PType): bool {...}{.inline, raises: [], tags: [].}

proc isGenericAlias(t: PType): bool {...}{.raises: [], tags: [].}

proc skipGenericAlias(t: PType): PType {...}{.raises: [], tags: [].}

proc sameFlags(a, b: PType): bool {...}{.inline, raises: [], tags: [].}

proc sameBackendType(x, y: PType): bool {...}{.
    raises: [Exception, ERecoverableError], tags: [RootEffect].}

proc compareTypes(x, y: PType; cmp: TDistinctCompare = dcEq;
                  flags: TTypeCmpFlags = {}): bool {...}{.
    raises: [Exception, ERecoverableError], tags: [RootEffect].}

proc inheritanceDiff(a, b: PType): int {...}{.raises: [Exception], tags: [RootEffect].}

proc commonSuperclass(a, b: PType): PType {...}{.raises: [Exception],
    tags: [RootEffect].}

proc matchType(a: PType; pattern: openArray[tuple[k: TTypeKind, i: int]];
               last: TTypeKind): bool {...}{.raises: [], tags: [].}

proc computeSize(conf: ConfigRef; typ: PType): BiggestInt {...}{.
    raises: [Exception, ValueError, IOError, ERecoverableError],
    tags: [RootEffect, WriteIOEffect, ReadIOEffect, ReadEnvEffect].}

proc getReturnType(s: PSym): PType {...}{.raises: [], tags: [].}

proc getAlign(conf: ConfigRef; typ: PType): BiggestInt {...}{.
    raises: [Exception, ValueError, IOError, ERecoverableError],
    tags: [RootEffect, WriteIOEffect, ReadIOEffect, ReadEnvEffect].}

proc getSize(conf: ConfigRef; typ: PType): BiggestInt {...}{.
    raises: [Exception, ValueError, IOError, ERecoverableError],
    tags: [RootEffect, WriteIOEffect, ReadIOEffect, ReadEnvEffect].}

proc containsGenericType(t: PType): bool {...}{.raises: [Exception],
    tags: [RootEffect].}

proc baseOfDistinct(t: PType): PType {...}{.raises: [], tags: [].}

proc safeInheritanceDiff(a, b: PType): int {...}{.raises: [Exception],
    tags: [RootEffect].}

proc compatibleEffects(formal, actual: PType): EffectsCompat {...}{.
    raises: [Exception], tags: [RootEffect].}

proc isCompileTimeOnly(t: PType): bool {...}{.inline, raises: [], tags: [].}

proc containsCompileTimeOnly(t: PType): bool {...}{.raises: [], tags: [].}

proc safeSkipTypes(t: PType; kinds: TTypeKinds): PType {...}{.raises: [], tags: [].}

proc classify(t: PType): OrdinalType {...}{.raises: [], tags: [].}

proc skipConv(n: PNode): PNode {...}{.raises: [], tags: [].}

proc skipHidden(n: PNode): PNode {...}{.raises: [], tags: [].}

proc skipConvTakeType(n: PNode): PNode {...}{.raises: [], tags: [].}

proc isEmptyContainer(t: PType): bool {...}{.raises: [], tags: [].}

proc takeType(formal, arg: PType): PType {...}{.raises: [], tags: [].}

proc skipHiddenSubConv(n: PNode): PNode {...}{.raises: [], tags: [].}

proc typeMismatch(conf: ConfigRef; info: TLineInfo; formal, actual: PType) {...}{.
    raises: [Exception, ValueError, IOError, ERecoverableError],
    tags: [RootEffect, WriteIOEffect, ReadIOEffect, ReadEnvEffect].}

proc isTupleRecursive(t: PType): bool {...}{.raises: [], tags: [].}

proc isException(t: PType): bool {...}{.raises: [], tags: [].}

proc isDefectException(t: PType): bool {...}{.raises: [], tags: [].}

proc isSinkTypeForParam(t: PType): bool {...}{.raises: [], tags: [].}

template `$`(typ: PType): string

template bindConcreteTypeToUserTypeClass(tc, concrete: PType)

template isResolvedUserTypeClass(t: PType): bool

template foldSizeOf(conf: ConfigRef; n: PNode; fallback: PNode): PNode

template foldAlignOf(conf: ConfigRef; n: PNode; fallback: PNode): PNode

template foldOffsetOf(conf: ConfigRef; n: PNode; fallback: PNode): PNode