Type members


class TastyBuffer(initialSize: Int)

A byte array buffer that can be filled with bytes or natural numbers in TASTY format, and that supports reading and patching addresses represented as natural numbers.

A byte array buffer that can be filled with bytes or natural numbers in TASTY format, and that supports reading and patching addresses represented as natural numbers.




We use BNF notation. Terminal symbols start with at least two consecutive upper case letters. Each terminal is represented as a single byte tag. Non-terminals are mixed case. Prefixes of the form lower case letter*_ are for explanation of semantic content only, they can be dropped without changing the grammar.


  LongInt       = Digit* StopDigit        -- big endian 2's complement, value fits in a Long w/o overflow
  Int           = LongInt                 -- big endian 2's complement, fits in an Int w/o overflow
  Nat           = LongInt                 -- non-negative value, fits in an Int without overflow
  Digit         = 0 | ... | 127
  StopDigit     = 128 | ... | 255         -- value = digit - 128


  File          = Header majorVersion_Nat minorVersion_Nat experimentalVersion_Nat VersionString UUID
                  nameTable_Length Name* Section*
  Header        = 0x5CA1AB1F
  UUID          = Byte*16                 -- random UUID
  VersionString = Length UTF8-CodePoint*  -- string that represents the compiler that produced the TASTy

  Section       = NameRef Length Bytes
  Length        = Nat                     -- length of rest of entry in bytes

  Name          = UTF8              Length UTF8-CodePoint*
                  QUALIFIED         Length qualified_NameRef selector_NameRef               -- A.B
                  EXPANDED          Length qualified_NameRef selector_NameRef               -- A$$B, semantically a NameKinds.ExpandedName
                  EXPANDPREFIX      Length qualified_NameRef selector_NameRef               -- A$B, prefix of expanded name, see NamedKinds.ExpandPrefixName

                  UNIQUE            Length separator_NameRef uniqid_Nat underlying_NameRef? -- Unique name A<separator><number>
                  DEFAULTGETTER     Length underlying_NameRef index_Nat                     -- DefaultGetter$<number>

                  SUPERACCESSOR     Length underlying_NameRef                               -- super$A
                  INLINEACCESSOR    Length underlying_NameRef                               -- inline$A
                  OBJECTCLASS       Length underlying_NameRef                               -- A$  (name of the module class for module A)
                  BODYRETAINER      Length underlying_NameRef                               -- A$retainedBody

                  SIGNED            Length original_NameRef resultSig_NameRef ParamSig*     -- name + signature
                  TARGETSIGNED      Length original_NameRef target_NameRef resultSig_NameRef ParamSig*

  ParamSig      = Int // If negative, the absolute value represents the length of a type parameter section
                      // If positive, this is a NameRef for the fully qualified name of a term parameter.

  NameRef       = Nat                    // ordinal number of name in name table, starting from 1.

Note: Unqualified names in the name table are strings. The context decides whether a name is a type-name or a term-name. The same string can represent both.

Standard-Section: "ASTs" TopLevelStat*

  TopLevelStat  = PACKAGE        Length Path TopLevelStat*                         -- package path { topLevelStats }

  Stat          = Term
                  TYPEDEF        Length NameRef (type_Term | Template) Modifier*   -- modifiers type name (= type | bounds)  |  modifiers class name template
                  IMPORT         Length qual_Term Selector*                        -- import qual selectors
                  EXPORT         Length qual_Term Selector*                        -- export qual selectors
  ValOrDefDef   = VALDEF         Length NameRef type_Term rhs_Term? Modifier*      -- modifiers val name : type (= rhs)?
                  DEFDEF         Length NameRef Param* returnType_Term rhs_Term?
                                        Modifier*                                  -- modifiers def name [typeparams] paramss : returnType (= rhs)?
  Selector      = IMPORTED              name_NameRef                               -- name, "_" for normal wildcards, "" for given wildcards
                  RENAMED               to_NameRef                                 -- => name
                  BOUNDED               type_Term                                  -- type bound

  TypeParam     = TYPEPARAM      Length NameRef type_Term Modifier*                -- modifiers name bounds
  TermParam     = PARAM          Length NameRef type_Term Modifier*                -- modifiers name : type.
                  EMPTYCLAUSE                                                      -- an empty parameter clause ()
                  SPLITCLAUSE                                                      -- splits two non-empty parameter clauses of the same kind
  Param         = TypeParam
  Template      = TEMPLATE       Length TypeParam* TermParam* parent_Term* Self?
                                        Stat*                                      -- [typeparams] paramss extends parents { self => stats }, where Stat* always starts with the primary constructor.
  Self          = SELFDEF               selfName_NameRef selfType_Term             -- selfName : selfType

  Term          = Path                                                             -- Paths represent both types and terms
                  IDENT                 NameRef Type                               -- Used when term ident’s type is not a TermRef
                  SELECT                possiblySigned_NameRef qual_Term           --
                  SELECTin       Length possiblySigned_NameRef qual_Term owner_Type --, referring to a symbol declared in owner that has the given signature (see note below)
                  QUALTHIS              typeIdent_Tree                             -- id.this, different from THIS in that it contains a qualifier ident with position.
                  NEW                   clsType_Term                               -- new cls
                  THROW                 throwableExpr_Term                         -- throw throwableExpr
                  NAMEDARG              paramName_NameRef arg_Term                 -- paramName = arg
                  APPLY          Length fn_Term arg_Term*                          -- fn(args)
                  TYPEAPPLY      Length fn_Term arg_Type*                          -- fn[args]
                  SUPER          Length this_Term mixinTypeIdent_Tree?             -- super[mixin]
                  TYPED          Length expr_Term ascriptionType_Term              -- expr: ascription
                  ASSIGN         Length lhs_Term rhs_Term                          -- lhs = rhs
                  BLOCK          Length expr_Term Stat*                            -- { stats; expr }
                  INLINED        Length expr_Term call_Term? ValOrDefDef*          -- Inlined code from call, with given body `expr` and given bindings
                  LAMBDA         Length meth_Term target_Type?                     -- Closure over method `f` of type `target` (omitted id `target` is a function type)
                  IF             Length [INLINE] cond_Term then_Term else_Term     -- inline? if cond then thenPart else elsePart
                  MATCH          Length (IMPLICIT | [INLINE] sel_Term) CaseDef*    -- (inline? sel | implicit) match caseDefs
                  TRY            Length expr_Term CaseDef* finalizer_Term?         -- try expr catch {casdeDef} (finally finalizer)?
                  RETURN         Length meth_ASTRef expr_Term?                     -- return expr?,  `methASTRef` is method from which is returned
                  WHILE          Length cond_Term body_Term                        -- while cond do body
                  REPEATED       Length elem_Type elem_Term*                       -- Varargs argument of type `elem`
                  SELECTouter    Length levels_Nat qual_Term underlying_Type       -- Follow `levels` outer links, starting from `qual`, with given `underlying` type
    -- patterns:
                  BIND           Length boundName_NameRef patType_Type pat_Term    -- name @ pat, wherev `patType` is the type of the bound symbol
                  ALTERNATIVE    Length alt_Term*                                  -- alt1 | ... | altn   as a pattern
                  UNAPPLY        Length fun_Term ImplicitArg* pat_Type pat_Term*   -- Unapply node `fun(_: pat_Type)(implicitArgs)` flowing into patterns `pat`.
    -- type trees:
                  IDENTtpt              NameRef Type                               -- Used for all type idents
                  SELECTtpt             NameRef qual_Term                          --
                  SINGLETONtpt          ref_Term                                   -- ref.type
                  REFINEDtpt     Length underlying_Term refinement_Stat*           -- underlying {refinements}
                  APPLIEDtpt     Length tycon_Term arg_Term*                       -- tycon [args]
                  LAMBDAtpt      Length TypeParam* body_Term                       -- [TypeParams] => body
                  TYPEBOUNDStpt  Length low_Term high_Term?                        -- >: low <: high
                  ANNOTATEDtpt   Length underlying_Term fullAnnotation_Term        -- underlying @ annotation
                  MATCHtpt       Length bound_Term? sel_Term CaseDef*              -- sel match { CaseDef } where `bound` is optional upper bound of all rhs
                  BYNAMEtpt             underlying_Term                            -- => underlying
                  SHAREDterm            term_ASTRef                                -- Link to previously serialized term
                  HOLE           Length idx_Nat arg_Tree*                          -- Hole where a splice goes with sequence number idx, splice is applied to arguments `arg`s

  CaseDef       = CASEDEF        Length pat_Term rhs_Tree guard_Tree?              -- case pat if guard => rhs
  ImplicitArg   = IMPLICITARG           arg_Term                                   -- implicit unapply argument

  ASTRef        = Nat                                                              -- Byte position in AST payload

  Path          = Constant
                  TERMREFdirect         sym_ASTRef                                 -- A reference to a local symbol (without a prefix). Reference is to definition node of symbol.
                  TERMREFsymbol         sym_ASTRef qual_Type                       -- A reference `qual.sym` to a local member with prefix `qual`
                  TERMREFpkg            fullyQualified_NameRef                     -- A reference to a package member with given fully qualified name
                  TERMREF               possiblySigned_NameRef qual_Type           -- A reference `` to a non-local member
                  TERMREFin      Length possiblySigned_NameRef qual_Type owner_Type -- A reference `` referring to a non-local symbol declared in owner that has the given signature (see note below)
                  THIS                  clsRef_Type                                -- cls.this
                  RECthis               recType_ASTRef                             -- The `this` in a recursive refined type `recType`.
                  SHAREDtype            path_ASTRef                                -- link to previously serialized path

  Constant      = UNITconst                                                        -- ()
                  FALSEconst                                                       -- false
                  TRUEconst                                                        -- true
                  BYTEconst             Int                                        -- A byte number
                  SHORTconst            Int                                        -- A short number
                  CHARconst             Nat                                        -- A character
                  INTconst              Int                                        -- An int number
                  LONGconst             LongInt                                    -- A long number
                  FLOATconst            Int                                        -- A float number
                  DOUBLEconst           LongInt                                    -- A double number
                  STRINGconst           NameRef                                    -- A string literal
                  NULLconst                                                        -- null
                  CLASSconst            Type                                       -- classOf[Type]

  Type          = Path                                                             -- Paths represent both types and terms
                  TYPEREFdirect         sym_ASTRef                                 -- A reference to a local symbol (without a prefix). Reference is to definition node of symbol.
                  TYPEREFsymbol         sym_ASTRef qual_Type                       -- A reference `qual.sym` to a local member with prefix `qual`
                  TYPEREFpkg            fullyQualified_NameRef                     -- A reference to a package member with given fully qualified name
                  TYPEREF               NameRef qual_Type                          -- A reference `` to a non-local member
                  TYPEREFin      Length NameRef qual_Type namespace_Type           -- A reference `` to a non-local member that's private in `namespace`.
                  RECtype               parent_Type                                -- A wrapper for recursive refined types
                  SUPERtype      Length this_Type underlying_Type                  -- A super type reference to `underlying`
                  REFINEDtype    Length refinement_NameRef underlying_Type info_Type -- underlying { refinement_name : info }
                  APPLIEDtype    Length tycon_Type arg_Type*                       -- tycon[args]
                  TYPEBOUNDS     Length lowOrAlias_Type high_Type? Variance*       -- = alias or >: low <: high, possibly with variances of lambda parameters
                  ANNOTATEDtype  Length underlying_Type annotation_Term            -- underlying @ annotation
                  ANDtype        Length left_Type right_Type                       -- left & right
                  ORtype         Length left_Type right_Type                       -- lefgt | right
                  MATCHtype      Length bound_Type sel_Type case_Type*             -- sel match {cases} with optional upper `bound`
                  MATCHCASEtype  Length pat_type rhs_Type                          -- match cases are MATCHCASEtypes or TYPELAMBDAtypes over MATCHCASEtypes
                  BIND           Length boundName_NameRef bounds_Type Modifier*    -- boundName @ bounds,  for type-variables defined in a type pattern
                  BYNAMEtype            underlying_Type                            -- => underlying
                  PARAMtype      Length binder_ASTRef paramNum_Nat                 -- A reference to parameter # paramNum in lambda type `binder`
                  POLYtype       Length result_Type TypesNames                     -- A polymorphic method type `[TypesNames]result`, used in refinements
                  METHODtype     Length result_Type TypesNames Modifier*           -- A method type `(Modifier* TypesNames)result`, needed for refinements, with optional modifiers for the parameters
                  TYPELAMBDAtype Length result_Type TypesNames                     -- A type lambda `[TypesNames] => result`
                  SHAREDtype            type_ASTRef                                -- link to previously serialized type
  TypesNames    = TypeName*
  TypeName      = typeOrBounds_ASTRef paramName_NameRef                            -- (`termName`: `type`)  or  (`typeName` `bounds`)

  Modifier      = PRIVATE                                                          -- private
                  PROTECTED                                                        -- protected
                  PRIVATEqualified     qualifier_Type                              -- private[qualifier]    (to be dropped(?)
                  PROTECTEDqualified   qualifier_Type                              -- protecred[qualifier]  (to be dropped(?)
                  ABSTRACT                                                         -- abstract
                  FINAL                                                            -- final
                  SEALED                                                           -- sealed
                  CASE                                                             -- case  (for classes or objects)
                  IMPLICIT                                                         -- implicit
                  GIVEN                                                            -- given
                  ERASED                                                           -- erased
                  LAZY                                                             -- lazy
                  OVERRIDE                                                         -- override
                  OPAQUE                                                           -- opaque, also used for classes containing opaque aliases
                  INLINE                                                           -- inline
                  MACRO                                                            -- Inline method containing toplevel splices
                  INLINEPROXY                                                      -- Symbol of binding with an argument to an inline method as rhs (TODO: do we still need this?)
                  STATIC                                                           -- Mapped to static Java member
                  OBJECT                                                           -- An object or its class
                  TRAIT                                                            -- A trait
                  ENUM                                                             -- A enum class or enum case
                  LOCAL                                                            -- private[this] or protected[this], used in conjunction with PRIVATE or PROTECTED
                  SYNTHETIC                                                        -- Generated by Scala compiler
                  ARTIFACT                                                         -- To be tagged Java Synthetic
                  MUTABLE                                                          -- A var
                  FIELDaccessor                                                    -- A getter or setter (note: the corresponding field is not serialized)
                  CASEaccessor                                                     -- A getter for a case class parameter
                  COVARIANT                                                        -- A type parameter marked “+”
                  CONTRAVARIANT                                                    -- A type parameter marked “-”
                  HASDEFAULT                                                       -- Parameter with default arg; method with default parameters (default arguments are separate methods with DEFAULTGETTER names)
                  STABLE                                                           -- Method that is assumed to be stable, i.e. its applications are legal paths
                  EXTENSION                                                        -- An extension method
                  PARAMsetter                                                      -- The setter part `x_=` of a var parameter `x` which itself is pickled as a PARAM
                  PARAMalias                                                       -- Parameter is alias of a superclass parameter
                  EXPORTED                                                         -- An export forwarder
                  OPEN                                                             -- an open class
                  INVISIBLE                                                        -- invisible during typechecking

  Variance      = STABLE                                                           -- invariant
                | COVARIANT
                | CONTRAVARIANT

  Annotation    = ANNOTATION     Length tycon_Type fullAnnotation_Term             -- An annotation, given (class) type of constructor, and full application tree

Note: The signature of a SELECTin or TERMREFin node is the signature of the selected symbol, not the signature of the reference. The latter undergoes an asSeenFrom but the former does not.

Note: Tree tags are grouped into 5 categories that determine what follows, and thus allow to compute the size of the tagged tree in a generic way.

  Category 1 (tags 1-59)   :  tag
  Category 2 (tags 60-89)  :  tag Nat
  Category 3 (tags 90-109) :  tag AST
  Category 4 (tags 110-127):  tag Nat AST
  Category 5 (tags 128-255):  tag Length <payload>

Standard-Section: "Positions" LinesSizes Assoc*

  LinesSizes    = Nat Nat*                 // Number of lines followed by the size of each line not counting the trailing `\n`

  Assoc         = Header offset_Delta? offset_Delta? point_Delta?
                | SOURCE nameref_Int
  Header        = addr_Delta +              // in one Nat: difference of address to last recorded node << 3 +
                  hasStartDiff +            // one bit indicating whether there follows a start address delta << 2
                  hasEndDiff +              // one bit indicating whether there follows an end address delta << 1
                  hasPoint                  // one bit indicating whether the new position has a point (i.e ^ position)
                                            // Nodes which have the same positions as their parents are omitted.
                                            // offset_Deltas give difference of start/end offset wrt to the
                                            // same offset in the previously recorded node (or 0 for the first recorded node)
  Delta         = Int                       // Difference between consecutive offsets,
  SOURCE        = 4                         // Impossible as header, since addr_Delta = 0 implies that we refer to the
                                            // same tree as the previous one, but then hasStartDiff = 1 implies that
                                            // the tree's range starts later than the range of itself.

All elements of a position section are serialized as Ints

Standard Section: "Comments" Comment*

  Comment       = Length Bytes LongInt      // Raw comment's bytes encoded as UTF-8, followed by the comment's coordinates.
sealed abstract case class TastyHeader(uuid: UUID, majorVersion: Int, minorVersion: Int, experimentalVersion: Int, toolingVersion: String)

The Tasty Header consists of four fields:

The Tasty Header consists of four fields:

  • uuid
  • contains a hash of the sections of the TASTy file
  • majorVersion
  • matching the TASTy format version that last broke backwards compatibility
  • minorVersion
  • matching the TASTy format version that last broke forward compatibility
  • experimentalVersion
  • 0 for final compiler version
  • positive for between minor versions and forward compatibility is broken since the previous stable version.
  • toolingVersion
  • arbitrary string representing the tooling that produced the TASTy
class TastyReader(val bytes: Array[Byte], start: Int, end: Int, val base: Int)

A byte array buffer that can be filled with bytes or natural numbers in TASTY format, and that supports reading and patching addresses represented as natural numbers.

A byte array buffer that can be filled with bytes or natural numbers in TASTY format, and that supports reading and patching addresses represented as natural numbers.

Value parameters:

The index referenced by the logical zero address Addr(0)


The array containing data


The position one greater than the last byte to be read


The position from which to read