Nim/compiler/ast.nim

#
#
#           The Nim Compiler
#        (c) Copyright 2015 Andreas Rumpf
#
#    See the file "copying.txt", included in this
#    distribution, for details about the copyright.
#

# abstract syntax tree + symbol table

import
  lineinfos, hashes, nversion, options, strutils, std / sha1, ropes, idents,
  intsets, idgen

type
  TCallingConvention* = enum
    ccDefault,                # proc has no explicit calling convention
    ccStdCall,                # procedure is stdcall
    ccCDecl,                  # cdecl
    ccSafeCall,               # safecall
    ccSysCall,                # system call
    ccInline,                 # proc should be inlined
    ccNoInline,               # proc should not be inlined
    ccFastCall,               # fastcall (pass parameters in registers)
    ccClosure,                # proc has a closure
    ccNoConvention            # needed for generating proper C procs sometimes

const
  CallingConvToStr*: array[TCallingConvention, string] = ["", "stdcall",
    "cdecl", "safecall", "syscall", "inline", "noinline", "fastcall",
    "closure", "noconv"]

type
  TNodeKind* = enum # order is extremely important, because ranges are used
                    # to check whether a node belongs to a certain class
    nkNone,               # unknown node kind: indicates an error
                          # Expressions:
                          # Atoms:
    nkEmpty,              # the node is empty
    nkIdent,              # node is an identifier
    nkSym,                # node is a symbol
    nkType,               # node is used for its typ field

    nkCharLit,            # a character literal ''
    nkIntLit,             # an integer literal
    nkInt8Lit,
    nkInt16Lit,
    nkInt32Lit,
    nkInt64Lit,
    nkUIntLit,            # an unsigned integer literal
    nkUInt8Lit,
    nkUInt16Lit,
    nkUInt32Lit,
    nkUInt64Lit,
    nkFloatLit,           # a floating point literal
    nkFloat32Lit,
    nkFloat64Lit,
    nkFloat128Lit,
    nkStrLit,             # a string literal ""
    nkRStrLit,            # a raw string literal r""
    nkTripleStrLit,       # a triple string literal """
    nkNilLit,             # the nil literal
                          # end of atoms
    nkComesFrom,          # "comes from" template/macro information for
                          # better stack trace generation
    nkDotCall,            # used to temporarily flag a nkCall node;
                          # this is used
                          # for transforming ``s.len`` to ``len(s)``

    nkCommand,            # a call like ``p 2, 4`` without parenthesis
    nkCall,               # a call like p(x, y) or an operation like +(a, b)
    nkCallStrLit,         # a call with a string literal
                          # x"abc" has two sons: nkIdent, nkRStrLit
                          # x"""abc""" has two sons: nkIdent, nkTripleStrLit
    nkInfix,              # a call like (a + b)
    nkPrefix,             # a call like !a
    nkPostfix,            # something like a! (also used for visibility)
    nkHiddenCallConv,     # an implicit type conversion via a type converter

    nkExprEqExpr,         # a named parameter with equals: ''expr = expr''
    nkExprColonExpr,      # a named parameter with colon: ''expr: expr''
    nkIdentDefs,          # a definition like `a, b: typeDesc = expr`
                          # either typeDesc or expr may be nil; used in
                          # formal parameters, var statements, etc.
    nkVarTuple,           # a ``var (a, b) = expr`` construct
    nkPar,                # syntactic (); may be a tuple constructor
    nkObjConstr,          # object constructor: T(a: 1, b: 2)
    nkCurly,              # syntactic {}
    nkCurlyExpr,          # an expression like a{i}
    nkBracket,            # syntactic []
    nkBracketExpr,        # an expression like a[i..j, k]
    nkPragmaExpr,         # an expression like a{.pragmas.}
    nkRange,              # an expression like i..j
    nkDotExpr,            # a.b
    nkCheckedFieldExpr,   # a.b, but b is a field that needs to be checked
    nkDerefExpr,          # a^
    nkIfExpr,             # if as an expression
    nkElifExpr,
    nkElseExpr,
    nkLambda,             # lambda expression
    nkDo,                 # lambda block appering as trailing proc param
    nkAccQuoted,          # `a` as a node

    nkTableConstr,        # a table constructor {expr: expr}
    nkBind,               # ``bind expr`` node
    nkClosedSymChoice,    # symbol choice node; a list of nkSyms (closed)
    nkOpenSymChoice,      # symbol choice node; a list of nkSyms (open)
    nkHiddenStdConv,      # an implicit standard type conversion
    nkHiddenSubConv,      # an implicit type conversion from a subtype
                          # to a supertype
    nkConv,               # a type conversion
    nkCast,               # a type cast
    nkStaticExpr,         # a static expr
    nkAddr,               # a addr expression
    nkHiddenAddr,         # implicit address operator
    nkHiddenDeref,        # implicit ^ operator
    nkObjDownConv,        # down conversion between object types
    nkObjUpConv,          # up conversion between object types
    nkChckRangeF,         # range check for floats
    nkChckRange64,        # range check for 64 bit ints
    nkChckRange,          # range check for ints
    nkStringToCString,    # string to cstring
    nkCStringToString,    # cstring to string
                          # end of expressions

    nkAsgn,               # a = b
    nkFastAsgn,           # internal node for a fast ``a = b``
                          # (no string copy)
    nkGenericParams,      # generic parameters
    nkFormalParams,       # formal parameters
    nkOfInherit,          # inherited from symbol

    nkImportAs,           # a 'as' b in an import statement
    nkProcDef,            # a proc
    nkMethodDef,          # a method
    nkConverterDef,       # a converter
    nkMacroDef,           # a macro
    nkTemplateDef,        # a template
    nkIteratorDef,        # an iterator

    nkOfBranch,           # used inside case statements
                          # for (cond, action)-pairs
    nkElifBranch,         # used in if statements
    nkExceptBranch,       # an except section
    nkElse,               # an else part
    nkAsmStmt,            # an assembler block
    nkPragma,             # a pragma statement
    nkPragmaBlock,        # a pragma with a block
    nkIfStmt,             # an if statement
    nkWhenStmt,           # a when expression or statement
    nkForStmt,            # a for statement
    nkParForStmt,         # a parallel for statement
    nkWhileStmt,          # a while statement
    nkCaseStmt,           # a case statement
    nkTypeSection,        # a type section (consists of type definitions)
    nkVarSection,         # a var section
    nkLetSection,         # a let section
    nkConstSection,       # a const section
    nkConstDef,           # a const definition
    nkTypeDef,            # a type definition
    nkYieldStmt,          # the yield statement as a tree
    nkDefer,              # the 'defer' statement
    nkTryStmt,            # a try statement
    nkFinally,            # a finally section
    nkRaiseStmt,          # a raise statement
    nkReturnStmt,         # a return statement
    nkBreakStmt,          # a break statement
    nkContinueStmt,       # a continue statement
    nkBlockStmt,          # a block statement
    nkStaticStmt,         # a static statement
    nkDiscardStmt,        # a discard statement
    nkStmtList,           # a list of statements
    nkImportStmt,         # an import statement
    nkImportExceptStmt,   # an import x except a statement
    nkExportStmt,         # an export statement
    nkExportExceptStmt,   # an 'export except' statement
    nkFromStmt,           # a from * import statement
    nkIncludeStmt,        # an include statement
    nkBindStmt,           # a bind statement
    nkMixinStmt,          # a mixin statement
    nkUsingStmt,          # an using statement
    nkCommentStmt,        # a comment statement
    nkStmtListExpr,       # a statement list followed by an expr; this is used
                          # to allow powerful multi-line templates
    nkBlockExpr,          # a statement block ending in an expr; this is used
                          # to allowe powerful multi-line templates that open a
                          # temporary scope
    nkStmtListType,       # a statement list ending in a type; for macros
    nkBlockType,          # a statement block ending in a type; for macros
                          # types as syntactic trees:

    nkWith,               # distinct with `foo`
    nkWithout,            # distinct without `foo`

    nkTypeOfExpr,         # type(1+2)
    nkObjectTy,           # object body
    nkTupleTy,            # tuple body
    nkTupleClassTy,       # tuple type class
    nkTypeClassTy,        # user-defined type class
    nkStaticTy,           # ``static[T]``
    nkRecList,            # list of object parts
    nkRecCase,            # case section of object
    nkRecWhen,            # when section of object
    nkRefTy,              # ``ref T``
    nkPtrTy,              # ``ptr T``
    nkVarTy,              # ``var T``
    nkConstTy,            # ``const T``
    nkMutableTy,          # ``mutable T``
    nkDistinctTy,         # distinct type
    nkProcTy,             # proc type
    nkIteratorTy,         # iterator type
    nkSharedTy,           # 'shared T'
                          # we use 'nkPostFix' for the 'not nil' addition
    nkEnumTy,             # enum body
    nkEnumFieldDef,       # `ident = expr` in an enumeration
    nkArgList,            # argument list
    nkPattern,            # a special pattern; used for matching
    nkReturnToken,        # token used for interpretation
    nkClosure,            # (prc, env)-pair (internally used for code gen)
    nkGotoState,          # used for the state machine (for iterators)
    nkState,              # give a label to a code section (for iterators)
    nkBreakState,         # special break statement for easier code generation
    nkFuncDef,            # a func
    nkTupleConstr         # a tuple constructor

  TNodeKinds* = set[TNodeKind]

type
  TSymFlag* = enum    # already 34 flags!
    sfUsed,           # read access of sym (for warnings) or simply used
    sfExported,       # symbol is exported from module
    sfFromGeneric,    # symbol is instantiation of a generic; this is needed
                      # for symbol file generation; such symbols should always
                      # be written into the ROD file
    sfGlobal,         # symbol is at global scope

    sfForward,        # symbol is forward declared
    sfImportc,        # symbol is external; imported
    sfExportc,        # symbol is exported (under a specified name)
    sfVolatile,       # variable is volatile
    sfRegister,       # variable should be placed in a register
    sfPure,           # object is "pure" that means it has no type-information
                      # enum is "pure", its values need qualified access
                      # variable is "pure"; it's an explicit "global"
    sfNoSideEffect,   # proc has no side effects
    sfSideEffect,     # proc may have side effects; cannot prove it has none
    sfMainModule,     # module is the main module
    sfSystemModule,   # module is the system module
    sfNoReturn,       # proc never returns (an exit proc)
    sfAddrTaken,      # the variable's address is taken (ex- or implicitly);
                      # *OR*: a proc is indirectly called (used as first class)
    sfCompilerProc,   # proc is a compiler proc, that is a C proc that is
                      # needed for the code generator
    sfProcvar,        # proc can be passed to a proc var
    sfDiscriminant,   # field is a discriminant in a record/object
    sfDeprecated,     # symbol is deprecated
    sfExplain,        # provide more diagnostics when this symbol is used
    sfError,          # usage of symbol should trigger a compile-time error
    sfShadowed,       # a symbol that was shadowed in some inner scope
    sfThread,         # proc will run as a thread
                      # variable is a thread variable
    sfCompileTime,    # proc can be evaluated at compile time
    sfConstructor,    # proc is a C++ constructor
    sfDispatcher,     # copied method symbol is the dispatcher
                      # deprecated and unused, except for the con
    sfBorrow,         # proc is borrowed
    sfInfixCall,      # symbol needs infix call syntax in target language;
                      # for interfacing with C++, JS
    sfNamedParamCall, # symbol needs named parameter call syntax in target
                      # language; for interfacing with Objective C
    sfDiscardable,    # returned value may be discarded implicitly
    sfOverriden,      # proc is overriden
    sfCallsite        # A flag for template symbols to tell the
                      # compiler it should use line information from
                      # the calling side of the macro, not from the
                      # implementation.
    sfGenSym          # symbol is 'gensym'ed; do not add to symbol table
    sfNonReloadable   # symbol will be left as-is when hot code reloading is on -
                      # meaning that it won't be renamed and/or changed in any way

  TSymFlags* = set[TSymFlag]

const
  sfNoInit* = sfMainModule       # don't generate code to init the variable

  sfImmediate* = sfDispatcher
    # macro or template is immediately expanded
    # without considering any possible overloads
  sfAllUntyped* = sfVolatile # macro or template is immediately expanded \
    # in a generic context

  sfDirty* = sfPure
    # template is not hygienic (old styled template)
    # module, compiled from a dirty-buffer

  sfAnon* = sfDiscardable
    # symbol name that was generated by the compiler
    # the compiler will avoid printing such names
    # in user messages.

  sfHoisted* = sfForward
    # an expression was hoised to an anonymous variable.
    # the flag is applied to the var/let symbol

  sfNoForward* = sfRegister
    # forward declarations are not required (per module)
  sfReorder* = sfForward
    # reordering pass is enabled

  sfCompileToCpp* = sfInfixCall       # compile the module as C++ code
  sfCompileToObjc* = sfNamedParamCall # compile the module as Objective-C code
  sfExperimental* = sfOverriden       # module uses the .experimental switch
  sfGoto* = sfOverriden               # var is used for 'goto' code generation
  sfWrittenTo* = sfBorrow             # param is assigned to
  sfEscapes* = sfProcvar              # param escapes
  sfBase* = sfDiscriminant
  sfIsSelf* = sfOverriden             # param is 'self'
  sfCustomPragma* = sfRegister        # symbol is custom pragma template

const
  # getting ready for the future expr/stmt merge
  nkWhen* = nkWhenStmt
  nkWhenExpr* = nkWhenStmt
  nkEffectList* = nkArgList
  # hacks ahead: an nkEffectList is a node with 4 children:
  exceptionEffects* = 0 # exceptions at position 0
  usesEffects* = 1      # read effects at position 1
  writeEffects* = 2     # write effects at position 2
  tagEffects* = 3       # user defined tag ('gc', 'time' etc.)
  pragmasEffects* = 4    # not an effect, but a slot for pragmas in proc type
  effectListLen* = 5    # list of effects list

type
  TTypeKind* = enum  # order is important!
                     # Don't forget to change hti.nim if you make a change here
                     # XXX put this into an include file to avoid this issue!
                     # several types are no longer used (guess which), but a
                     # spot in the sequence is kept for backwards compatibility
                     # (apparently something with bootstrapping)
                     # if you need to add a type, they can apparently be reused
    tyNone, tyBool, tyChar,
    tyEmpty, tyAlias, tyNil, tyExpr, tyStmt, tyTypeDesc,
    tyGenericInvocation, # ``T[a, b]`` for types to invoke
    tyGenericBody,       # ``T[a, b, body]`` last parameter is the body
    tyGenericInst,       # ``T[a, b, realInstance]`` instantiated generic type
                         # realInstance will be a concrete type like tyObject
                         # unless this is an instance of a generic alias type.
                         # then realInstance will be the tyGenericInst of the
                         # completely (recursively) resolved alias.

    tyGenericParam,      # ``a`` in the above patterns
    tyDistinct,
    tyEnum,
    tyOrdinal,           # integer types (including enums and boolean)
    tyArray,
    tyObject,
    tyTuple,
    tySet,
    tyRange,
    tyPtr, tyRef,
    tyVar,
    tySequence,
    tyProc,
    tyPointer, tyOpenArray,
    tyString, tyCString, tyForward,
    tyInt, tyInt8, tyInt16, tyInt32, tyInt64, # signed integers
    tyFloat, tyFloat32, tyFloat64, tyFloat128,
    tyUInt, tyUInt8, tyUInt16, tyUInt32, tyUInt64,
    tyOwned, tySink, tyLent,
    tyVarargs,
    tyUncheckedArray
      # An array with boundaries [0,+∞]

    tyProxy # used as errornous type (for idetools)

    tyBuiltInTypeClass
      # Type such as the catch-all object, tuple, seq, etc

    tyUserTypeClass
      # the body of a user-defined type class

    tyUserTypeClassInst
      # Instance of a parametric user-defined type class.
      # Structured similarly to tyGenericInst.
      # tyGenericInst represents concrete types, while
      # this is still a "generic param" that will bind types
      # and resolves them during sigmatch and instantiation.

    tyCompositeTypeClass
      # Type such as seq[Number]
      # The notes for tyUserTypeClassInst apply here as well
      # sons[0]: the original expression used by the user.
      # sons[1]: fully expanded and instantiated meta type
      # (potentially following aliases)

    tyInferred
      # In the initial state `base` stores a type class constraining
      # the types that can be inferred. After a candidate type is
      # selected, it's stored in `lastSon`. Between `base` and `lastSon`
      # there may be 0, 2 or more types that were also considered as
      # possible candidates in the inference process (i.e. lastSon will
      # be updated to store a type best conforming to all candidates)

    tyAnd, tyOr, tyNot
      # boolean type classes such as `string|int`,`not seq`,
      # `Sortable and Enumable`, etc

    tyAnything
      # a type class matching any type

    tyStatic
      # a value known at compile type (the underlying type is .base)

    tyFromExpr
      # This is a type representing an expression that depends
      # on generic parameters (the expression is stored in t.n)
      # It will be converted to a real type only during generic
      # instantiation and prior to this it has the potential to
      # be any type.

    tyOpt
      # Builtin optional type

    tyVoid
      # now different from tyEmpty, hurray!

static:
  # remind us when TTypeKind stops to fit in a single 64-bit word
  assert TTypeKind.high.ord <= 63

const
  tyPureObject* = tyTuple
  GcTypeKinds* = {tyRef, tySequence, tyString}
  tyError* = tyProxy # as an errornous node should match everything
  tyUnknown* = tyFromExpr

  tyUnknownTypes* = {tyError, tyFromExpr}

  tyTypeClasses* = {tyBuiltInTypeClass, tyCompositeTypeClass,
                    tyUserTypeClass, tyUserTypeClassInst,
                    tyAnd, tyOr, tyNot, tyAnything}

  tyMetaTypes* = {tyGenericParam, tyTypeDesc, tyExpr} + tyTypeClasses
  tyUserTypeClasses* = {tyUserTypeClass, tyUserTypeClassInst}

type
  TTypeKinds* = set[TTypeKind]

  TNodeFlag* = enum
    nfNone,
    nfBase2,    # nfBase10 is default, so not needed
    nfBase8,
    nfBase16,
    nfAllConst, # used to mark complex expressions constant; easy to get rid of
                # but unfortunately it has measurable impact for compilation
                # efficiency
    nfTransf,   # node has been transformed
    nfNoRewrite # node should not be transformed anymore
    nfSem       # node has been checked for semantics
    nfLL        # node has gone through lambda lifting
    nfDotField  # the call can use a dot operator
    nfDotSetter # the call can use a setter dot operarator
    nfExplicitCall # x.y() was used instead of x.y
    nfExprCall  # this is an attempt to call a regular expression
    nfIsRef     # this node is a 'ref' node; used for the VM
    nfPreventCg # this node should be ignored by the codegen
    nfBlockArg  # this a stmtlist appearing in a call (e.g. a do block)
    nfFromTemplate # a top-level node returned from a template
    nfDefaultParam # an automatically inserter default parameter
    nfDefaultRefsParam # a default param value references another parameter
                       # the flag is applied to proc default values and to calls
    nfExecuteOnReload  # A top-level statement that will be executed during reloads

  TNodeFlags* = set[TNodeFlag]
  TTypeFlag* = enum   # keep below 32 for efficiency reasons (now: beyond that)
    tfVarargs,        # procedure has C styled varargs
                      # tyArray type represeting a varargs list
    tfNoSideEffect,   # procedure type does not allow side effects
    tfFinal,          # is the object final?
    tfInheritable,    # is the object inheritable?
    tfAcyclic,        # type is acyclic (for GC optimization)
    tfEnumHasHoles,   # enum cannot be mapped into a range
    tfShallow,        # type can be shallow copied on assignment
    tfThread,         # proc type is marked as ``thread``; alias for ``gcsafe``
    tfFromGeneric,    # type is an instantiation of a generic; this is needed
                      # because for instantiations of objects, structural
                      # type equality has to be used
    tfUnresolved,     # marks unresolved typedesc/static params: e.g.
                      # proc foo(T: typedesc, list: seq[T]): var T
                      # proc foo(L: static[int]): array[L, int]
                      # can be attached to ranges to indicate that the range
                      # can be attached to generic procs with free standing
                      # type parameters: e.g. proc foo[T]()
                      # depends on unresolved static params.
    tfResolved        # marks a user type class, after it has been bound to a
                      # concrete type (lastSon becomes the concrete type)
    tfRetType,        # marks return types in proc (used to detect type classes
                      # used as return types for return type inference)
    tfCapturesEnv,    # whether proc really captures some environment
    tfByCopy,         # pass object/tuple by copy (C backend)
    tfByRef,          # pass object/tuple by reference (C backend)
    tfIterator,       # type is really an iterator, not a tyProc
    tfPartial,        # type is declared as 'partial'
    tfNotNil,         # type cannot be 'nil'

    tfNeedsInit,      # type constains a "not nil" constraint somewhere or some
                      # other type so that it requires initialization
    tfVarIsPtr,       # 'var' type is translated like 'ptr' even in C++ mode
    tfHasMeta,        # type contains "wildcard" sub-types such as generic params
                      # or other type classes
    tfHasGCedMem,     # type contains GC'ed memory
    tfPacked
    tfHasStatic
    tfGenericTypeParam
    tfImplicitTypeParam
    tfInferrableStatic
    tfConceptMatchedTypeSym
    tfExplicit        # for typedescs, marks types explicitly prefixed with the
                      # `type` operator (e.g. type int)
    tfWildcard        # consider a proc like foo[T, I](x: Type[T, I])
                      # T and I here can bind to both typedesc and static types
                      # before this is determined, we'll consider them to be a
                      # wildcard type.
    tfHasAsgn         # type has overloaded assignment operator
    tfBorrowDot       # distinct type borrows '.'
    tfTriggersCompileTime # uses the NimNode type which make the proc
                          # implicitly '.compiletime'
    tfRefsAnonObj     # used for 'ref object' and 'ptr object'
    tfCovariant       # covariant generic param mimicing a ptr type
    tfWeakCovariant   # covariant generic param mimicing a seq/array type
    tfContravariant   # contravariant generic param

  TTypeFlags* = set[TTypeFlag]

  TSymKind* = enum        # the different symbols (start with the prefix sk);
                          # order is important for the documentation generator!
    skUnknown,            # unknown symbol: used for parsing assembler blocks
                          # and first phase symbol lookup in generics
    skConditional,        # symbol for the preprocessor (may become obsolete)
    skDynLib,             # symbol represents a dynamic library; this is used
                          # internally; it does not exist in Nim code
    skParam,              # a parameter
    skGenericParam,       # a generic parameter; eq in ``proc x[eq=`==`]()``
    skTemp,               # a temporary variable (introduced by compiler)
    skModule,             # module identifier
    skType,               # a type
    skVar,                # a variable
    skLet,                # a 'let' symbol
    skConst,              # a constant
    skResult,             # special 'result' variable
    skProc,               # a proc
    skFunc,               # a func
    skMethod,             # a method
    skIterator,           # an iterator
    skConverter,          # a type converter
    skMacro,              # a macro
    skTemplate,           # a template; currently also misused for user-defined
                          # pragmas
    skField,              # a field in a record or object
    skEnumField,          # an identifier in an enum
    skForVar,             # a for loop variable
    skLabel,              # a label (for block statement)
    skStub,               # symbol is a stub and not yet loaded from the ROD
                          # file (it is loaded on demand, which may
                          # mean: never)
    skPackage,            # symbol is a package (used for canonicalization)
    skAlias               # an alias (needs to be resolved immediately)
  TSymKinds* = set[TSymKind]

const
  routineKinds* = {skProc, skFunc, skMethod, skIterator,
                   skConverter, skMacro, skTemplate}
  tfIncompleteStruct* = tfVarargs
  tfUnion* = tfNoSideEffect
  tfGcSafe* = tfThread
  tfObjHasKids* = tfEnumHasHoles
  tfReturnsNew* = tfInheritable
  skError* = skUnknown

  # type flags that are essential for type equality:
  eqTypeFlags* = {tfIterator, tfNotNil, tfVarIsPtr}

type
  TMagic* = enum # symbols that require compiler magic:
    mNone,
    mDefined, mDefinedInScope, mCompiles, mArrGet, mArrPut, mAsgn,
    mLow, mHigh, mSizeOf, mAlignOf, mOffsetOf, mTypeTrait,
    mIs, mOf, mAddr, mType, mTypeOf,
    mRoof, mPlugin, mEcho, mShallowCopy, mSlurp, mStaticExec, mStatic,
    mParseExprToAst, mParseStmtToAst, mExpandToAst, mQuoteAst,
    mUnaryLt, mInc, mDec, mOrd,
    mNew, mNewFinalize, mNewSeq, mNewSeqOfCap,
    mLengthOpenArray, mLengthStr, mLengthArray, mLengthSeq,
    mXLenStr, mXLenSeq,
    mIncl, mExcl, mCard, mChr,
    mGCref, mGCunref,
    mAddI, mSubI, mMulI, mDivI, mModI,
    mSucc, mPred,
    mAddF64, mSubF64, mMulF64, mDivF64,
    mShrI, mShlI, mAshrI, mBitandI, mBitorI, mBitxorI,
    mMinI, mMaxI,
    mMinF64, mMaxF64,
    mAddU, mSubU, mMulU, mDivU, mModU,
    mEqI, mLeI, mLtI,
    mEqF64, mLeF64, mLtF64,
    mLeU, mLtU,
    mLeU64, mLtU64,
    mEqEnum, mLeEnum, mLtEnum,
    mEqCh, mLeCh, mLtCh,
    mEqB, mLeB, mLtB,
    mEqRef, mEqUntracedRef, mLePtr, mLtPtr,
    mXor, mEqCString, mEqProc,
    mUnaryMinusI, mUnaryMinusI64, mAbsI, mNot,
    mUnaryPlusI, mBitnotI,
    mUnaryPlusF64, mUnaryMinusF64, mAbsF64,
    mZe8ToI, mZe8ToI64,
    mZe16ToI, mZe16ToI64,
    mZe32ToI64, mZeIToI64,
    mToU8, mToU16, mToU32,
    mToFloat, mToBiggestFloat,
    mToInt, mToBiggestInt,
    mCharToStr, mBoolToStr, mIntToStr, mInt64ToStr, mFloatToStr, mCStrToStr,
    mStrToStr, mEnumToStr,
    mAnd, mOr,
    mEqStr, mLeStr, mLtStr,
    mEqSet, mLeSet, mLtSet, mMulSet, mPlusSet, mMinusSet, mSymDiffSet,
    mConStrStr, mSlice,
    mDotDot, # this one is only necessary to give nice compile time warnings
    mFields, mFieldPairs, mOmpParFor,
    mAppendStrCh, mAppendStrStr, mAppendSeqElem,
    mInRange, mInSet, mRepr, mExit,
    mSetLengthStr, mSetLengthSeq,
    mIsPartOf, mAstToStr, mParallel,
    mSwap, mIsNil, mArrToSeq, mCopyStr, mCopyStrLast,
    mNewString, mNewStringOfCap, mParseBiggestFloat,
    mMove, mWasMoved, mDestroy,
    mReset,
    mArray, mOpenArray, mRange, mSet, mSeq, mOpt, mVarargs,
    mRef, mPtr, mVar, mDistinct, mVoid, mTuple,
    mOrdinal,
    mInt, mInt8, mInt16, mInt32, mInt64,
    mUInt, mUInt8, mUInt16, mUInt32, mUInt64,
    mFloat, mFloat32, mFloat64, mFloat128,
    mBool, mChar, mString, mCstring,
    mPointer, mEmptySet, mIntSetBaseType, mNil, mExpr, mStmt, mTypeDesc,
    mVoidType, mPNimrodNode, mShared, mGuarded, mLock, mSpawn, mDeepCopy,
    mIsMainModule, mCompileDate, mCompileTime, mProcCall,
    mCpuEndian, mHostOS, mHostCPU, mBuildOS, mBuildCPU, mAppType,
    mNaN, mInf, mNegInf,
    mCompileOption, mCompileOptionArg,
    mNLen, mNChild, mNSetChild, mNAdd, mNAddMultiple, mNDel,
    mNKind, mNSymKind,

    mNccValue, mNccInc, mNcsAdd, mNcsIncl, mNcsLen, mNcsAt,
    mNctPut, mNctLen, mNctGet, mNctHasNext, mNctNext,

    mNIntVal, mNFloatVal, mNSymbol, mNIdent, mNGetType, mNStrVal, mNSetIntVal,
    mNSetFloatVal, mNSetSymbol, mNSetIdent, mNSetType, mNSetStrVal, mNLineInfo,
    mNNewNimNode, mNCopyNimNode, mNCopyNimTree, mStrToIdent, mNSigHash,
    mNBindSym, mLocals, mNCallSite,
    mEqIdent, mEqNimrodNode, mSameNodeType, mGetImpl, mNGenSym,
    mNHint, mNWarning, mNError,
    mInstantiationInfo, mGetTypeInfo,
    mNimvm, mIntDefine, mStrDefine, mBoolDefine, mRunnableExamples,
    mException, mBuiltinType, mSymOwner, mUncheckedArray, mGetImplTransf,
    mSymIsInstantiationOf

# things that we can evaluate safely at compile time, even if not asked for it:
const
  ctfeWhitelist* = {mNone, mUnaryLt, mSucc,
    mPred, mInc, mDec, mOrd, mLengthOpenArray,
    mLengthStr, mLengthArray, mLengthSeq, mXLenStr, mXLenSeq,
    mArrGet, mArrPut, mAsgn, mDestroy,
    mIncl, mExcl, mCard, mChr,
    mAddI, mSubI, mMulI, mDivI, mModI,
    mAddF64, mSubF64, mMulF64, mDivF64,
    mShrI, mShlI, mBitandI, mBitorI, mBitxorI,
    mMinI, mMaxI,
    mMinF64, mMaxF64,
    mAddU, mSubU, mMulU, mDivU, mModU,
    mEqI, mLeI, mLtI,
    mEqF64, mLeF64, mLtF64,
    mLeU, mLtU,
    mLeU64, mLtU64,
    mEqEnum, mLeEnum, mLtEnum,
    mEqCh, mLeCh, mLtCh,
    mEqB, mLeB, mLtB,
    mEqRef, mEqProc, mEqUntracedRef, mLePtr, mLtPtr, mEqCString, mXor,
    mUnaryMinusI, mUnaryMinusI64, mAbsI, mNot, mUnaryPlusI, mBitnotI,
    mUnaryPlusF64, mUnaryMinusF64, mAbsF64,
    mZe8ToI, mZe8ToI64,
    mZe16ToI, mZe16ToI64,
    mZe32ToI64, mZeIToI64,
    mToU8, mToU16, mToU32,
    mToFloat, mToBiggestFloat,
    mToInt, mToBiggestInt,
    mCharToStr, mBoolToStr, mIntToStr, mInt64ToStr, mFloatToStr, mCStrToStr,
    mStrToStr, mEnumToStr,
    mAnd, mOr,
    mEqStr, mLeStr, mLtStr,
    mEqSet, mLeSet, mLtSet, mMulSet, mPlusSet, mMinusSet, mSymDiffSet,
    mConStrStr, mAppendStrCh, mAppendStrStr, mAppendSeqElem,
    mInRange, mInSet, mRepr,
    mCopyStr, mCopyStrLast}

type
  PNode* = ref TNode
  TNodeSeq* = seq[PNode]
  PType* = ref TType
  PSym* = ref TSym
  TNode*{.final, acyclic.} = object # on a 32bit machine, this takes 32 bytes
    when defined(useNodeIds):
      id*: int
    typ*: PType
    info*: TLineInfo
    flags*: TNodeFlags
    case kind*: TNodeKind
    of nkCharLit..nkUInt64Lit:
      intVal*: BiggestInt
    of nkFloatLit..nkFloat128Lit:
      floatVal*: BiggestFloat
    of nkStrLit..nkTripleStrLit:
      strVal*: string
    of nkSym:
      sym*: PSym
    of nkIdent:
      ident*: PIdent
    else:
      sons*: TNodeSeq
    comment*: string

  TStrTable* = object         # a table[PIdent] of PSym
    counter*: int
    data*: seq[PSym]

  # -------------- backend information -------------------------------
  TLocKind* = enum
    locNone,                  # no location
    locTemp,                  # temporary location
    locLocalVar,              # location is a local variable
    locGlobalVar,             # location is a global variable
    locParam,                 # location is a parameter
    locField,                 # location is a record field
    locExpr,                  # "location" is really an expression
    locProc,                  # location is a proc (an address of a procedure)
    locData,                  # location is a constant
    locCall,                  # location is a call expression
    locOther                  # location is something other
  TLocFlag* = enum
    lfIndirect,               # backend introduced a pointer
    lfFullExternalName, # only used when 'conf.cmd == cmdPretty': Indicates
      # that the symbol has been imported via 'importc: "fullname"' and
      # no format string.
    lfNoDeepCopy,             # no need for a deep copy
    lfNoDecl,                 # do not declare it in C
    lfDynamicLib,             # link symbol to dynamic library
    lfExportLib,              # export symbol for dynamic library generation
    lfHeader,                 # include header file for symbol
    lfImportCompilerProc,     # ``importc`` of a compilerproc
    lfSingleUse               # no location yet and will only be used once
  TStorageLoc* = enum
    OnUnknown,                # location is unknown (stack, heap or static)
    OnStatic,                 # in a static section
    OnStack,                  # location is on hardware stack
    OnHeap                    # location is on heap or global
                              # (reference counting needed)
  TLocFlags* = set[TLocFlag]
  TLoc* = object
    k*: TLocKind              # kind of location
    storage*: TStorageLoc
    flags*: TLocFlags         # location's flags
    lode*: PNode              # Node where the location came from; can be faked
    r*: Rope                  # rope value of location (code generators)

  # ---------------- end of backend information ------------------------------

  TLibKind* = enum
    libHeader, libDynamic

  TLib* = object              # also misused for headers!
    kind*: TLibKind
    generated*: bool          # needed for the backends:
    isOverriden*: bool
    name*: Rope
    path*: PNode              # can be a string literal!


  CompilesId* = int ## id that is used for the caching logic within
                    ## ``system.compiles``. See the seminst module.
  TInstantiation* = object
    sym*: PSym
    concreteTypes*: seq[PType]
    compilesId*: CompilesId

  PInstantiation* = ref TInstantiation

  TScope* = object
    depthLevel*: int
    symbols*: TStrTable
    parent*: PScope

  PScope* = ref TScope

  PLib* = ref TLib
  TSym* {.acyclic.} = object of TIdObj
    # proc and type instantiations are cached in the generic symbol
    case kind*: TSymKind
    of skType, skGenericParam:
      typeInstCache*: seq[PType]
    of routineKinds:
      procInstCache*: seq[PInstantiation]
      gcUnsafetyReason*: PSym  # for better error messages wrt gcsafe
      transformedBody*: PNode  # cached body after transf pass
    of skModule, skPackage:
      # modules keep track of the generic symbols they use from other modules.
      # this is because in incremental compilation, when a module is about to
      # be replaced with a newer version, we must decrement the usage count
      # of all previously used generics.
      # For 'import as' we copy the module symbol but shallowCopy the 'tab'
      # and set the 'usedGenerics' to ... XXX gah! Better set module.name
      # instead? But this doesn't work either. --> We need an skModuleAlias?
      # No need, just leave it as skModule but set the owner accordingly and
      # check for the owner when touching 'usedGenerics'.
      usedGenerics*: seq[PInstantiation]
      tab*: TStrTable         # interface table for modules
    of skLet, skVar, skField, skForVar:
      guard*: PSym
      bitsize*: int
    else: nil
    magic*: TMagic
    typ*: PType
    name*: PIdent
    info*: TLineInfo
    owner*: PSym
    flags*: TSymFlags
    ast*: PNode               # syntax tree of proc, iterator, etc.:
                              # the whole proc including header; this is used
                              # for easy generation of proper error messages
                              # for variant record fields the discriminant
                              # expression
                              # for modules, it's a placeholder for compiler
                              # generated code that will be appended to the
                              # module after the sem pass (see appendToModule)
    options*: TOptions
    position*: int            # used for many different things:
                              # for enum fields its position;
                              # for fields its offset
                              # for parameters its position
                              # for a conditional:
                              # 1 iff the symbol is defined, else 0
                              # (or not in symbol table)
                              # for modules, an unique index corresponding
                              # to the module's fileIdx
                              # for variables a slot index for the evaluator
                              # for routines a superop-ID
    offset*: int              # offset of record field
    loc*: TLoc
    annex*: PLib              # additional fields (seldom used, so we use a
                              # reference to another object to save space)
    constraint*: PNode        # additional constraints like 'lit|result'; also
                              # misused for the codegenDecl pragma in the hope
                              # it won't cause problems
                              # for skModule the string literal to output for
                              # deprecated modules.
    when defined(nimsuggest):
      allUsages*: seq[TLineInfo]

  TTypeSeq* = seq[PType]
  TLockLevel* = distinct int16
  TType* {.acyclic.} = object of TIdObj # \
                              # types are identical iff they have the
                              # same id; there may be multiple copies of a type
                              # in memory!
    kind*: TTypeKind          # kind of type
    callConv*: TCallingConvention # for procs
    flags*: TTypeFlags        # flags of the type
    sons*: TTypeSeq           # base types, etc.
    n*: PNode                 # node for types:
                              # for range types a nkRange node
                              # for record types a nkRecord node
                              # for enum types a list of symbols
                              # for tyInt it can be the int literal
                              # for procs and tyGenericBody, it's the
                              # formal param list
                              # for concepts, the concept body
                              # else: unused
    owner*: PSym              # the 'owner' of the type
    sym*: PSym                # types have the sym associated with them
                              # it is used for converting types to strings
    destructor*: PSym         # destructor. warning: nil here may not necessary
                              # mean that there is no destructor.
                              # see instantiateDestructor in semdestruct.nim
    deepCopy*: PSym           # overriden 'deepCopy' operation
    assignment*: PSym         # overriden '=' operation
    sink*: PSym               # overriden '=sink' operation
    methods*: seq[(int,PSym)] # attached methods
    size*: BiggestInt         # the size of the type in bytes
                              # -1 means that the size is unkwown
    align*: int16             # the type's alignment requirements
    lockLevel*: TLockLevel    # lock level as required for deadlock checking
    loc*: TLoc
    typeInst*: PType          # for generic instantiations the tyGenericInst that led to this
                              # type.
    uniqueId*: int            # due to a design mistake, we need to keep the real ID here as it
                              # required by the --incremental:on mode.

  TPair* = object
    key*, val*: RootRef

  TPairSeq* = seq[TPair]

  TIdPair* = object
    key*: PIdObj
    val*: RootRef

  TIdPairSeq* = seq[TIdPair]
  TIdTable* = object # the same as table[PIdent] of PObject
    counter*: int
    data*: TIdPairSeq

  TIdNodePair* = object
    key*: PIdObj
    val*: PNode

  TIdNodePairSeq* = seq[TIdNodePair]
  TIdNodeTable* = object # the same as table[PIdObj] of PNode
    counter*: int
    data*: TIdNodePairSeq

  TNodePair* = object
    h*: Hash                 # because it is expensive to compute!
    key*: PNode
    val*: int

  TNodePairSeq* = seq[TNodePair]
  TNodeTable* = object # the same as table[PNode] of int;
                                # nodes are compared by structure!
    counter*: int
    data*: TNodePairSeq

  TObjectSeq* = seq[RootRef]
  TObjectSet* = object
    counter*: int
    data*: TObjectSeq

  TImplication* = enum
    impUnknown, impNo, impYes

# BUGFIX: a module is overloadable so that a proc can have the
# same name as an imported module. This is necessary because of
# the poor naming choices in the standard library.

const
  OverloadableSyms* = {skProc, skFunc, skMethod, skIterator,
    skConverter, skModule, skTemplate, skMacro}

  GenericTypes*: TTypeKinds = {tyGenericInvocation, tyGenericBody,
    tyGenericParam}

  StructuralEquivTypes*: TTypeKinds = {tyNil, tyTuple, tyArray,
    tySet, tyRange, tyPtr, tyRef, tyVar, tyLent, tySequence, tyProc, tyOpenArray,
    tyVarargs}

  ConcreteTypes*: TTypeKinds = { # types of the expr that may occur in::
                                 # var x = expr
    tyBool, tyChar, tyEnum, tyArray, tyObject,
    tySet, tyTuple, tyRange, tyPtr, tyRef, tyVar, tyLent, tySequence, tyProc,
    tyPointer,
    tyOpenArray, tyString, tyCString, tyInt..tyInt64, tyFloat..tyFloat128,
    tyUInt..tyUInt64}
  IntegralTypes* = {tyBool, tyChar, tyEnum, tyInt..tyInt64,
    tyFloat..tyFloat128, tyUInt..tyUInt64}
  ConstantDataTypes*: TTypeKinds = {tyArray, tySet,
                                    tyTuple, tySequence}
  NilableTypes*: TTypeKinds = {tyPointer, tyCString, tyRef, tyPtr,
    tyProc, tyError}
  ExportableSymKinds* = {skVar, skConst, skProc, skFunc, skMethod, skType,
    skIterator,
    skMacro, skTemplate, skConverter, skEnumField, skLet, skStub, skAlias}
  PersistentNodeFlags*: TNodeFlags = {nfBase2, nfBase8, nfBase16,
                                      nfDotSetter, nfDotField,
                                      nfIsRef, nfPreventCg, nfLL,
                                      nfFromTemplate, nfDefaultRefsParam,
                                      nfExecuteOnReload}
  namePos* = 0
  patternPos* = 1    # empty except for term rewriting macros
  genericParamsPos* = 2
  paramsPos* = 3
  pragmasPos* = 4
  miscPos* = 5  # used for undocumented and hacky stuff
  bodyPos* = 6       # position of body; use rodread.getBody() instead!
  resultPos* = 7
  dispatcherPos* = 8 # caution: if method has no 'result' it can be position 7!

  nkCallKinds* = {nkCall, nkInfix, nkPrefix, nkPostfix,
                  nkCommand, nkCallStrLit, nkHiddenCallConv}
  nkIdentKinds* = {nkIdent, nkSym, nkAccQuoted, nkOpenSymChoice,
                   nkClosedSymChoice}

  nkPragmaCallKinds* = {nkExprColonExpr, nkCall, nkCallStrLit}
  nkLiterals* = {nkCharLit..nkTripleStrLit}
  nkFloatLiterals* = {nkFloatLit..nkFloat128Lit}
  nkLambdaKinds* = {nkLambda, nkDo}
  declarativeDefs* = {nkProcDef, nkFuncDef, nkMethodDef, nkIteratorDef, nkConverterDef}
  procDefs* = nkLambdaKinds + declarativeDefs

  nkSymChoices* = {nkClosedSymChoice, nkOpenSymChoice}
  nkStrKinds* = {nkStrLit..nkTripleStrLit}

  skLocalVars* = {skVar, skLet, skForVar, skParam, skResult}
  skProcKinds* = {skProc, skFunc, skTemplate, skMacro, skIterator,
                  skMethod, skConverter}

var ggDebug* {.deprecated.}: bool ## convenience switch for trying out things
#var
#  gMainPackageId*: int

proc isCallExpr*(n: PNode): bool =
  result = n.kind in nkCallKinds

proc discardSons*(father: PNode)

proc len*(n: PNode): int {.inline.} =
  when defined(nimNoNilSeqs):
    result = len(n.sons)
  else:
    if isNil(n.sons): result = 0
    else: result = len(n.sons)

proc safeLen*(n: PNode): int {.inline.} =
  ## works even for leaves.
  if n.kind in {nkNone..nkNilLit}: result = 0
  else: result = len(n)

proc safeArrLen*(n: PNode): int {.inline.} =
  ## works for array-like objects (strings passed as openArray in VM).
  if n.kind in {nkStrLit..nkTripleStrLit}:result = len(n.strVal)
  elif n.kind in {nkNone..nkFloat128Lit}: result = 0
  else: result = len(n)

proc add*(father, son: PNode) =
  assert son != nil
  when not defined(nimNoNilSeqs):
    if isNil(father.sons): father.sons = @[]
  add(father.sons, son)

type Indexable = PNode | PType

template `[]`*(n: Indexable, i: int): Indexable = n.sons[i]
template `[]=`*(n: Indexable, i: int; x: Indexable) = n.sons[i] = x

template `[]`*(n: Indexable, i: BackwardsIndex): Indexable = n[n.len - i.int]
template `[]=`*(n: Indexable, i: BackwardsIndex; x: Indexable) = n[n.len - i.int] = x

when defined(useNodeIds):
  const nodeIdToDebug* = -1 # 299750 # 300761 #300863 # 300879
  var gNodeId: int

proc newNode*(kind: TNodeKind): PNode =
  new(result)
  result.kind = kind
  #result.info = UnknownLineInfo() inlined:
  result.info.fileIndex = InvalidFileIdx
  result.info.col = int16(-1)
  result.info.line = uint16(0)
  when defined(useNodeIds):
    result.id = gNodeId
    if result.id == nodeIdToDebug:
      echo "KIND ", result.kind
      writeStackTrace()
    inc gNodeId

proc newTree*(kind: TNodeKind; children: varargs[PNode]): PNode =
  result = newNode(kind)
  if children.len > 0:
    result.info = children[0].info
  result.sons = @children

template previouslyInferred*(t: PType): PType =
  if t.sons.len > 1: t.lastSon else: nil

proc newSym*(symKind: TSymKind, name: PIdent, owner: PSym,
             info: TLineInfo; options: TOptions = {}): PSym =
  # generates a symbol and initializes the hash field too
  new(result)
  result.name = name
  result.kind = symKind
  result.flags = {}
  result.info = info
  result.options = options
  result.owner = owner
  result.offset = -1
  result.id = getID()
  when debugIds:
    registerId(result)

proc astdef*(s: PSym): PNode =
  # get only the definition (initializer) portion of the ast
  if s.ast != nil and s.ast.kind == nkIdentDefs:
    s.ast[2]
  else:
    s.ast

proc isMetaType*(t: PType): bool =
  return t.kind in tyMetaTypes or
         (t.kind == tyStatic and t.n == nil) or
         tfHasMeta in t.flags

proc isUnresolvedStatic*(t: PType): bool =
  return t.kind == tyStatic and t.n == nil

proc linkTo*(t: PType, s: PSym): PType {.discardable.} =
  t.sym = s
  s.typ = t
  result = t

proc linkTo*(s: PSym, t: PType): PSym {.discardable.} =
  t.sym = s
  s.typ = t
  result = s

template fileIdx*(c: PSym): FileIndex =
  # XXX: this should be used only on module symbols
  c.position.FileIndex

template filename*(c: PSym): string =
  # XXX: this should be used only on module symbols
  c.position.FileIndex.toFilename

proc appendToModule*(m: PSym, n: PNode) =
  ## The compiler will use this internally to add nodes that will be
  ## appended to the module after the sem pass
  if m.ast == nil:
    m.ast = newNode(nkStmtList)
    m.ast.sons = @[n]
  else:
    assert m.ast.kind == nkStmtList
    m.ast.sons.add(n)

const                         # for all kind of hash tables:
  GrowthFactor* = 2           # must be power of 2, > 0
  StartSize* = 8              # must be power of 2, > 0

proc copyStrTable*(dest: var TStrTable, src: TStrTable) =
  dest.counter = src.counter
  setLen(dest.data, len(src.data))
  for i in countup(0, high(src.data)): dest.data[i] = src.data[i]

proc copyIdTable*(dest: var TIdTable, src: TIdTable) =
  dest.counter = src.counter
  newSeq(dest.data, len(src.data))
  for i in countup(0, high(src.data)): dest.data[i] = src.data[i]

proc copyObjectSet*(dest: var TObjectSet, src: TObjectSet) =
  dest.counter = src.counter
  setLen(dest.data, len(src.data))
  for i in countup(0, high(src.data)): dest.data[i] = src.data[i]

proc discardSons*(father: PNode) =
  when defined(nimNoNilSeqs):
    father.sons = @[]
  else:
    father.sons = nil

proc withInfo*(n: PNode, info: TLineInfo): PNode =
  n.info = info
  return n

proc newIdentNode*(ident: PIdent, info: TLineInfo): PNode =
  result = newNode(nkIdent)
  result.ident = ident
  result.info = info

proc newSymNode*(sym: PSym): PNode =
  result = newNode(nkSym)
  result.sym = sym
  result.typ = sym.typ
  result.info = sym.info

proc newSymNode*(sym: PSym, info: TLineInfo): PNode =
  result = newNode(nkSym)
  result.sym = sym
  result.typ = sym.typ
  result.info = info

proc newNodeI*(kind: TNodeKind, info: TLineInfo): PNode =
  new(result)
  result.kind = kind
  result.info = info
  when defined(useNodeIds):
    result.id = gNodeId
    if result.id == nodeIdToDebug:
      echo "KIND ", result.kind
      writeStackTrace()
    inc gNodeId

proc newNodeI*(kind: TNodeKind, info: TLineInfo, children: int): PNode =
  new(result)
  result.kind = kind
  result.info = info
  if children > 0:
    newSeq(result.sons, children)
  when defined(useNodeIds):
    result.id = gNodeId
    if result.id == nodeIdToDebug:
      echo "KIND ", result.kind
      writeStackTrace()
    inc gNodeId

proc newNode*(kind: TNodeKind, info: TLineInfo, sons: TNodeSeq = @[],
             typ: PType = nil): PNode =
  new(result)
  result.kind = kind
  result.info = info
  result.typ = typ
  # XXX use shallowCopy here for ownership transfer:
  result.sons = sons
  when defined(useNodeIds):
    result.id = gNodeId
    if result.id == nodeIdToDebug:
      echo "KIND ", result.kind
      writeStackTrace()
    inc gNodeId

proc newNodeIT*(kind: TNodeKind, info: TLineInfo, typ: PType): PNode =
  result = newNode(kind)
  result.info = info
  result.typ = typ

proc newIntNode*(kind: TNodeKind, intVal: BiggestInt): PNode =
  result = newNode(kind)
  result.intVal = intVal

proc newIntTypeNode*(kind: TNodeKind, intVal: BiggestInt, typ: PType): PNode =
  result = newIntNode(kind, intVal)
  result.typ = typ

proc newFloatNode*(kind: TNodeKind, floatVal: BiggestFloat): PNode =
  result = newNode(kind)
  result.floatVal = floatVal

proc newStrNode*(kind: TNodeKind, strVal: string): PNode =
  result = newNode(kind)
  result.strVal = strVal

proc newStrNode*(strVal: string; info: TLineInfo): PNode =
  result = newNodeI(nkStrLit, info)
  result.strVal = strVal

proc addSon*(father, son: PNode) =
  assert son != nil
  when not defined(nimNoNilSeqs):
    if isNil(father.sons): father.sons = @[]
  add(father.sons, son)

proc newProcNode*(kind: TNodeKind, info: TLineInfo, body: PNode,
                 params,
                 name, pattern, genericParams,
                 pragmas, exceptions: PNode): PNode =
  result = newNodeI(kind, info)
  result.sons = @[name, pattern, genericParams, params,
                  pragmas, exceptions, body]

const
  UnspecifiedLockLevel* = TLockLevel(-1'i16)
  MaxLockLevel* = 1000'i16
  UnknownLockLevel* = TLockLevel(1001'i16)

proc `$`*(x: TLockLevel): string =
  if x.ord == UnspecifiedLockLevel.ord: result = "<unspecified>"
  elif x.ord == UnknownLockLevel.ord: result = "<unknown>"
  else: result = $int16(x)

proc `$`*(s: PSym): string =
  if s != nil:
    result = s.name.s & "@" & $s.id
  else:
    result = "<nil>"

proc newType*(kind: TTypeKind, owner: PSym): PType =
  new(result)
  result.kind = kind
  result.owner = owner
  result.size = -1
  result.align = -1            # default alignment
  result.id = getID()
  result.uniqueId = result.id
  result.lockLevel = UnspecifiedLockLevel
  when debugIds:
    registerId(result)
  when false:
    if result.id == 76426:
      echo "KNID ", kind
      writeStackTrace()

proc mergeLoc(a: var TLoc, b: TLoc) =
  if a.k == low(a.k): a.k = b.k
  if a.storage == low(a.storage): a.storage = b.storage
  a.flags = a.flags + b.flags
  if a.lode == nil: a.lode = b.lode
  if a.r == nil: a.r = b.r

proc newSons*(father: PNode, length: int) =
  when defined(nimNoNilSeqs):
    setLen(father.sons, length)
  else:
    if isNil(father.sons):
      newSeq(father.sons, length)
    else:
      setLen(father.sons, length)

proc newSons*(father: PType, length: int) =
  when defined(nimNoNilSeqs):
    setLen(father.sons, length)
  else:
    if isNil(father.sons):
      newSeq(father.sons, length)
    else:
      setLen(father.sons, length)

proc sonsLen*(n: PType): int = n.sons.len
proc len*(n: PType): int = n.sons.len
proc sonsLen*(n: PNode): int = n.sons.len
proc lastSon*(n: PNode): PNode = n.sons[^1]
proc lastSon*(n: PType): PType = n.sons[^1]

proc assignType*(dest, src: PType) =
  dest.kind = src.kind
  dest.flags = src.flags
  dest.callConv = src.callConv
  dest.n = src.n
  dest.size = src.size
  dest.align = src.align
  dest.destructor = src.destructor
  dest.deepCopy = src.deepCopy
  dest.sink = src.sink
  dest.assignment = src.assignment
  dest.lockLevel = src.lockLevel
  # this fixes 'type TLock = TSysLock':
  if src.sym != nil:
    if dest.sym != nil:
      dest.sym.flags = dest.sym.flags + (src.sym.flags-{sfExported})
      if dest.sym.annex == nil: dest.sym.annex = src.sym.annex
      mergeLoc(dest.sym.loc, src.sym.loc)
    else:
      dest.sym = src.sym
  newSons(dest, sonsLen(src))
  for i in countup(0, sonsLen(src) - 1): dest.sons[i] = src.sons[i]

proc copyType*(t: PType, owner: PSym, keepId: bool): PType =
  result = newType(t.kind, owner)
  assignType(result, t)
  if keepId:
    result.id = t.id
  else:
    when debugIds: registerId(result)
  result.sym = t.sym          # backend-info should not be copied

proc exactReplica*(t: PType): PType = copyType(t, t.owner, true)

proc copySym*(s: PSym): PSym =
  result = newSym(s.kind, s.name, s.owner, s.info, s.options)
  #result.ast = nil            # BUGFIX; was: s.ast which made problems
  result.typ = s.typ
  when debugIds: registerId(result)
  result.flags = s.flags
  result.magic = s.magic
  if s.kind == skModule:
    copyStrTable(result.tab, s.tab)
  result.options = s.options
  result.position = s.position
  result.loc = s.loc
  result.annex = s.annex      # BUGFIX
  if result.kind in {skVar, skLet, skField}:
    result.guard = s.guard

proc createModuleAlias*(s: PSym, newIdent: PIdent, info: TLineInfo;
                        options: TOptions): PSym =
  result = newSym(s.kind, newIdent, s.owner, info, options)
  # keep ID!
  result.ast = s.ast
  result.id = s.id
  result.flags = s.flags
  system.shallowCopy(result.tab, s.tab)
  result.options = s.options
  result.position = s.position
  result.loc = s.loc
  result.annex = s.annex
  # XXX once usedGenerics is used, ensure module aliases keep working!
  assert s.usedGenerics.len == 0

proc initStrTable*(x: var TStrTable) =
  x.counter = 0
  newSeq(x.data, StartSize)

proc newStrTable*: TStrTable =
  initStrTable(result)

proc initIdTable*(x: var TIdTable) =
  x.counter = 0
  newSeq(x.data, StartSize)

proc newIdTable*: TIdTable =
  initIdTable(result)

proc resetIdTable*(x: var TIdTable) =
  x.counter = 0
  # clear and set to old initial size:
  setLen(x.data, 0)
  setLen(x.data, StartSize)

proc initObjectSet*(x: var TObjectSet) =
  x.counter = 0
  newSeq(x.data, StartSize)

proc initIdNodeTable*(x: var TIdNodeTable) =
  x.counter = 0
  newSeq(x.data, StartSize)

proc initNodeTable*(x: var TNodeTable) =
  x.counter = 0
  newSeq(x.data, StartSize)

proc skipTypes*(t: PType, kinds: TTypeKinds): PType =
  ## Used throughout the compiler code to test whether a type tree contains or
  ## doesn't contain a specific type/types - it is often the case that only the
  ## last child nodes of a type tree need to be searched. This is a really hot
  ## path within the compiler!
  result = t
  while result.kind in kinds: result = lastSon(result)

proc skipTypes*(t: PType, kinds: TTypeKinds; maxIters: int): PType =
  result = t
  var i = maxIters
  while result.kind in kinds:
    result = lastSon(result)
    dec i
    if i == 0: return nil

proc skipTypesOrNil*(t: PType, kinds: TTypeKinds): PType =
  ## same as skipTypes but handles 'nil'
  result = t
  while result != nil and result.kind in kinds:
    if result.len == 0: return nil
    result = lastSon(result)

proc isGCedMem*(t: PType): bool {.inline.} =
  result = t.kind in {tyString, tyRef, tySequence} or
           t.kind == tyProc and t.callConv == ccClosure

proc propagateToOwner*(owner, elem: PType) =
  const HaveTheirOwnEmpty = {tySequence, tyOpt, tySet, tyPtr, tyRef, tyProc}
  owner.flags = owner.flags + (elem.flags * {tfHasMeta, tfTriggersCompileTime})
  if tfNotNil in elem.flags:
    if owner.kind in {tyGenericInst, tyGenericBody, tyGenericInvocation}:
      owner.flags.incl tfNotNil
    elif owner.kind notin HaveTheirOwnEmpty:
      owner.flags.incl tfNeedsInit

  if tfNeedsInit in elem.flags:
    if owner.kind in HaveTheirOwnEmpty: discard
    else: owner.flags.incl tfNeedsInit

  if elem.isMetaType:
    owner.flags.incl tfHasMeta

  if tfHasAsgn in elem.flags:
    let o2 = owner.skipTypes({tyGenericInst, tyAlias, tySink})
    if o2.kind in {tyTuple, tyObject, tyArray,
                   tySequence, tyOpt, tySet, tyDistinct}:
      o2.flags.incl tfHasAsgn
      owner.flags.incl tfHasAsgn

  if owner.kind notin {tyProc, tyGenericInst, tyGenericBody,
                       tyGenericInvocation, tyPtr}:
    let elemB = elem.skipTypes({tyGenericInst, tyAlias, tySink})
    if elemB.isGCedMem or tfHasGCedMem in elemB.flags:
      # for simplicity, we propagate this flag even to generics. We then
      # ensure this doesn't bite us in sempass2.
      owner.flags.incl tfHasGCedMem

proc rawAddSon*(father, son: PType) =
  when not defined(nimNoNilSeqs):
    if isNil(father.sons): father.sons = @[]
  add(father.sons, son)
  if not son.isNil: propagateToOwner(father, son)

proc rawAddSonNoPropagationOfTypeFlags*(father, son: PType) =
  when not defined(nimNoNilSeqs):
    if isNil(father.sons): father.sons = @[]
  add(father.sons, son)

proc addSonNilAllowed*(father, son: PNode) =
  when not defined(nimNoNilSeqs):
    if isNil(father.sons): father.sons = @[]
  add(father.sons, son)

proc delSon*(father: PNode, idx: int) =
  when defined(nimNoNilSeqs):
    if father.len == 0: return
  else:
    if isNil(father.sons): return
  var length = sonsLen(father)
  for i in countup(idx, length - 2): father.sons[i] = father.sons[i + 1]
  setLen(father.sons, length - 1)

proc copyNode*(src: PNode): PNode =
  # does not copy its sons!
  if src == nil:
    return nil
  result = newNode(src.kind)
  result.info = src.info
  result.typ = src.typ
  result.flags = src.flags * PersistentNodeFlags
  result.comment = src.comment
  when defined(useNodeIds):
    if result.id == nodeIdToDebug:
      echo "COMES FROM ", src.id
  case src.kind
  of nkCharLit..nkUInt64Lit: result.intVal = src.intVal
  of nkFloatLiterals: result.floatVal = src.floatVal
  of nkSym: result.sym = src.sym
  of nkIdent: result.ident = src.ident
  of nkStrLit..nkTripleStrLit: result.strVal = src.strVal
  else: discard

proc shallowCopy*(src: PNode): PNode =
  # does not copy its sons, but provides space for them:
  if src == nil: return nil
  result = newNode(src.kind)
  result.info = src.info
  result.typ = src.typ
  result.flags = src.flags * PersistentNodeFlags
  result.comment = src.comment
  when defined(useNodeIds):
    if result.id == nodeIdToDebug:
      echo "COMES FROM ", src.id
  case src.kind
  of nkCharLit..nkUInt64Lit: result.intVal = src.intVal
  of nkFloatLiterals: result.floatVal = src.floatVal
  of nkSym: result.sym = src.sym
  of nkIdent: result.ident = src.ident
  of nkStrLit..nkTripleStrLit: result.strVal = src.strVal
  else: newSeq(result.sons, sonsLen(src))

proc copyTree*(src: PNode): PNode =
  # copy a whole syntax tree; performs deep copying
  if src == nil:
    return nil
  result = newNode(src.kind)
  result.info = src.info
  result.typ = src.typ
  result.flags = src.flags * PersistentNodeFlags
  result.comment = src.comment
  when defined(useNodeIds):
    if result.id == nodeIdToDebug:
      echo "COMES FROM ", src.id
  case src.kind
  of nkCharLit..nkUInt64Lit: result.intVal = src.intVal
  of nkFloatLiterals: result.floatVal = src.floatVal
  of nkSym: result.sym = src.sym
  of nkIdent: result.ident = src.ident
  of nkStrLit..nkTripleStrLit: result.strVal = src.strVal
  else:
    newSeq(result.sons, sonsLen(src))
    for i in countup(0, sonsLen(src) - 1):
      result.sons[i] = copyTree(src.sons[i])

proc hasSonWith*(n: PNode, kind: TNodeKind): bool =
  for i in countup(0, sonsLen(n) - 1):
    if n.sons[i].kind == kind:
      return true
  result = false

proc hasNilSon*(n: PNode): bool =
  for i in countup(0, safeLen(n) - 1):
    if n.sons[i] == nil:
      return true
    elif hasNilSon(n.sons[i]):
      return true
  result = false

proc containsNode*(n: PNode, kinds: TNodeKinds): bool =
  if n == nil: return
  case n.kind
  of nkEmpty..nkNilLit: result = n.kind in kinds
  else:
    for i in countup(0, sonsLen(n) - 1):
      if n.kind in kinds or containsNode(n.sons[i], kinds): return true

proc hasSubnodeWith*(n: PNode, kind: TNodeKind): bool =
  case n.kind
  of nkEmpty..nkNilLit: result = n.kind == kind
  else:
    for i in countup(0, sonsLen(n) - 1):
      if (n.sons[i].kind == kind) or hasSubnodeWith(n.sons[i], kind):
        return true
    result = false

proc getInt*(a: PNode): BiggestInt =
  case a.kind
  of nkCharLit..nkUInt64Lit: result = a.intVal
  else:
    raiseRecoverableError("cannot extract number from invalid AST node")
    #internalError(a.info, "getInt")
    #doAssert false, "getInt"
    #result = 0

proc getFloat*(a: PNode): BiggestFloat =
  case a.kind
  of nkFloatLiterals: result = a.floatVal
  else:
    raiseRecoverableError("cannot extract number from invalid AST node")
    #doAssert false, "getFloat"
    #internalError(a.info, "getFloat")
    #result = 0.0

proc getStr*(a: PNode): string =
  case a.kind
  of nkStrLit..nkTripleStrLit: result = a.strVal
  of nkNilLit:
    # let's hope this fixes more problems than it creates:
    when defined(nimNoNilSeqs):
      result = ""
    else:
      result = nil
  else:
    raiseRecoverableError("cannot extract string from invalid AST node")
    #doAssert false, "getStr"
    #internalError(a.info, "getStr")
    #result = ""

proc getStrOrChar*(a: PNode): string =
  case a.kind
  of nkStrLit..nkTripleStrLit: result = a.strVal
  of nkCharLit..nkUInt64Lit: result = $chr(int(a.intVal))
  else:
    raiseRecoverableError("cannot extract string from invalid AST node")
    #doAssert false, "getStrOrChar"
    #internalError(a.info, "getStrOrChar")
    #result = ""

proc isGenericRoutine*(s: PSym): bool =
  case s.kind
  of skProcKinds:
    result = sfFromGeneric in s.flags or
             (s.ast != nil and s.ast[genericParamsPos].kind != nkEmpty)
  else: discard

proc skipGenericOwner*(s: PSym): PSym =
  ## Generic instantiations are owned by their originating generic
  ## symbol. This proc skips such owners and goes straight to the owner
  ## of the generic itself (the module or the enclosing proc).
  result = if s.kind in skProcKinds and sfFromGeneric in s.flags:
             s.owner.owner
           else:
             s.owner

proc originatingModule*(s: PSym): PSym =
  result = s.owner
  while result.kind != skModule: result = result.owner

proc isRoutine*(s: PSym): bool {.inline.} =
  result = s.kind in skProcKinds

proc isCompileTimeProc*(s: PSym): bool {.inline.} =
  result = s.kind == skMacro or
           s.kind == skProc and sfCompileTime in s.flags

proc isRunnableExamples*(n: PNode): bool =
  # Templates and generics don't perform symbol lookups.
  result = n.kind == nkSym and n.sym.magic == mRunnableExamples or
    n.kind == nkIdent and n.ident.s == "runnableExamples"

proc requiredParams*(s: PSym): int =
  # Returns the number of required params (without default values)
  # XXX: Perhaps we can store this in the `offset` field of the
  # symbol instead?
  for i in 1 ..< s.typ.len:
    if s.typ.n[i].sym.ast != nil:
      return i - 1
  return s.typ.len - 1

proc hasPattern*(s: PSym): bool {.inline.} =
  result = isRoutine(s) and s.ast.sons[patternPos].kind != nkEmpty

iterator items*(n: PNode): PNode =
  for i in 0..<n.safeLen: yield n.sons[i]

iterator pairs*(n: PNode): tuple[i: int, n: PNode] =
  for i in 0..<n.safeLen: yield (i, n.sons[i])

proc isAtom*(n: PNode): bool {.inline.} =
  result = n.kind >= nkNone and n.kind <= nkNilLit

proc isEmptyType*(t: PType): bool {.inline.} =
  ## 'void' and 'stmt' types are often equivalent to 'nil' these days:
  result = t == nil or t.kind in {tyVoid, tyStmt}

proc makeStmtList*(n: PNode): PNode =
  if n.kind == nkStmtList:
    result = n
  else:
    result = newNodeI(nkStmtList, n.info)
    result.add n

proc skipStmtList*(n: PNode): PNode =
  if n.kind in {nkStmtList, nkStmtListExpr}:
    for i in 0 .. n.len-2:
      if n[i].kind notin {nkEmpty, nkCommentStmt}: return n
    result = n.lastSon
  else:
    result = n

proc toVar*(typ: PType): PType =
  ## If ``typ`` is not a tyVar then it is converted into a `var <typ>` and
  ## returned. Otherwise ``typ`` is simply returned as-is.
  result = typ
  if typ.kind != tyVar:
    result = newType(tyVar, typ.owner)
    rawAddSon(result, typ)

proc toRef*(typ: PType): PType =
  ## If ``typ`` is a tyObject then it is converted into a `ref <typ>` and
  ## returned. Otherwise ``typ`` is simply returned as-is.
  if typ.skipTypes({tyAlias, tyGenericInst}).kind == tyObject:
    result = newType(tyRef, typ.owner)
    rawAddSon(result, typ)

proc toObject*(typ: PType): PType =
  ## If ``typ`` is a tyRef then its immediate son is returned (which in many
  ## cases should be a ``tyObject``).
  ## Otherwise ``typ`` is simply returned as-is.
  let t = typ.skipTypes({tyAlias, tyGenericInst})
  if t.kind == tyRef: t.lastSon
  else: typ

proc isException*(t: PType): bool =
  # check if `y` is object type and it inherits from Exception
  assert(t != nil)

  if t.kind notin {tyObject, tyGenericInst}:
    return false

  var base = t
  while base != nil and base.kind in {tyRef, tyObject, tyGenericInst}:
    if base.sym != nil and base.sym.magic == mException:
      return true
    base = base.lastSon
  return false

proc isImportedException*(t: PType; conf: ConfigRef): bool =
  assert t != nil

  if optNoCppExceptions in conf.globalOptions:
    return false

  let base = t.skipTypes({tyAlias, tyPtr, tyDistinct, tyGenericInst})

  if base.sym != nil and {sfCompileToCpp, sfImportc} * base.sym.flags != {}:
    result = true

proc isInfixAs*(n: PNode): bool =
  return n.kind == nkInfix and n[0].kind == nkIdent and n[0].ident.s == "as"

proc findUnresolvedStatic*(n: PNode): PNode =
  if n.kind == nkSym and n.typ.kind == tyStatic and n.typ.n == nil:
    return n

  for son in n:
    let n = son.findUnresolvedStatic
    if n != nil: return n

  return nil

when false:
  proc containsNil*(n: PNode): bool =
    # only for debugging
    if n.isNil: return true
    for i in 0 ..< n.safeLen:
      if n[i].containsNil: return true

template hasDestructor*(t: PType): bool = tfHasAsgn in t.flags
template incompleteType*(t: PType): bool =
  t.sym != nil and {sfForward, sfNoForward} * t.sym.flags == {sfForward}

template typeCompleted*(s: PSym) =
  incl s.flags, sfNoForward

template getBody*(s: PSym): PNode = s.ast[bodyPos]

template detailedInfo*(sym: PSym): string =
  sym.name.s