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view gcc/ada/sem_type.ads @ 111:04ced10e8804
gcc 7
| author | kono |
|---|---|
| date | Fri, 27 Oct 2017 22:46:09 +0900 |
| parents | |
| children | 84e7813d76e9 |
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------------------------------------------------------------------------------ -- -- -- GNAT COMPILER COMPONENTS -- -- -- -- S E M _ T Y P E -- -- -- -- S p e c -- -- -- -- Copyright (C) 1992-2013, Free Software Foundation, Inc. -- -- -- -- GNAT is free software; you can redistribute it and/or modify it under -- -- terms of the GNU General Public License as published by the Free Soft- -- -- ware Foundation; either version 3, or (at your option) any later ver- -- -- sion. GNAT is distributed in the hope that it will be useful, but WITH- -- -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License -- -- for more details. You should have received a copy of the GNU General -- -- Public License distributed with GNAT; see file COPYING3. If not, go to -- -- http://www.gnu.org/licenses for a complete copy of the license. -- -- -- -- GNAT was originally developed by the GNAT team at New York University. -- -- Extensive contributions were provided by Ada Core Technologies Inc. -- -- -- ------------------------------------------------------------------------------ -- This unit contains the routines used to handle type determination, -- including the routine used to support overload resolution. with Types; use Types; package Sem_Type is --------------------------------------------- -- Data Structures for Overload Resolution -- --------------------------------------------- -- To determine the unique meaning of an identifier, overload resolution -- may have to be performed if the visibility rules alone identify more -- than one possible entity as the denotation of a given identifier. When -- the visibility rules find such a potential ambiguity, the set of -- possible interpretations must be attached to the identifier, and -- overload resolution must be performed over the innermost enclosing -- complete context. At the end of the resolution, either a single -- interpretation is found for all identifiers in the context, or else a -- type error (invalid type or ambiguous reference) must be signalled. -- The set of interpretations of a given name is stored in a data structure -- that is separate from the syntax tree, because it corresponds to -- transient information. The interpretations themselves are stored in -- table All_Interp. A mapping from tree nodes to sets of interpretations -- called Interp_Map, is maintained by the overload resolution routines. -- Both these structures are initialized at the beginning of every complete -- context. -- Corresponding to the set of interpretations for a given overloadable -- identifier, there is a set of possible types corresponding to the types -- that the overloaded call may return. We keep a 1-to-1 correspondence -- between interpretations and types: for user-defined subprograms the type -- is the declared return type. For operators, the type is determined by -- the type of the arguments. If the arguments themselves are overloaded, -- we enter the operator name in the names table for each possible result -- type. In most cases, arguments are not overloaded and only one -- interpretation is present anyway. type Interp is record Nam : Entity_Id; Typ : Entity_Id; Abstract_Op : Entity_Id := Empty; end record; -- Entity Abstract_Op is set to the abstract operation which potentially -- disables the interpretation in Ada 2005 mode. No_Interp : constant Interp := (Empty, Empty, Empty); type Interp_Index is new Int; --------------------- -- Error Reporting -- --------------------- -- A common error is the use of an operator in infix notation on arguments -- of a type that is not directly visible. Rather than diagnosing a type -- mismatch, it is better to indicate that the type can be made use-visible -- with the appropriate use clause. The global variable Candidate_Type is -- set in Add_One_Interp whenever an interpretation might be legal for an -- operator if the type were directly visible. This variable is used in -- sem_ch4 when no legal interpretation is found. Candidate_Type : Entity_Id; ----------------- -- Subprograms -- ----------------- procedure Init_Interp_Tables; -- Invoked by gnatf when processing multiple files procedure Collect_Interps (N : Node_Id); -- Invoked when the name N has more than one visible interpretation. This -- is the high level routine which accumulates the possible interpretations -- of the node. The first meaning and type of N have already been stored -- in N. If the name is an expanded name, the homonyms are only those that -- belong to the same scope. function Is_Invisible_Operator (N : Node_Id; T : Entity_Id) return Boolean; -- Check whether a predefined operation with universal operands appears in -- a context in which the operators of the expected type are not visible. procedure List_Interps (Nam : Node_Id; Err : Node_Id); -- List candidate interpretations of an overloaded name. Used for various -- error reports. procedure Add_One_Interp (N : Node_Id; E : Entity_Id; T : Entity_Id; Opnd_Type : Entity_Id := Empty); -- Add (E, T) to the list of interpretations of the node being resolved. -- For calls and operators, i.e. for nodes that have a name field, E is an -- overloadable entity, and T is its type. For constructs such as indexed -- expressions, the caller sets E equal to T, because the overloading comes -- from other fields, and the node itself has no name to resolve. Hidden -- denotes whether an interpretation has been disabled by an abstract -- operator. Add_One_Interp includes semantic processing to deal with -- adding entries that hide one another etc. -- -- For operators, the legality of the operation depends on the visibility -- of T and its scope. If the operator is an equality or comparison, T is -- always Boolean, and we use Opnd_Type, which is a candidate type for one -- of the operands of N, to check visibility. procedure End_Interp_List; -- End the list of interpretations of current node procedure Get_First_Interp (N : Node_Id; I : out Interp_Index; It : out Interp); -- Initialize iteration over set of interpretations for Node N. The first -- interpretation is placed in It, and I is initialized for subsequent -- calls to Get_Next_Interp. procedure Get_Next_Interp (I : in out Interp_Index; It : out Interp); -- Iteration step over set of interpretations. Using the value in I, which -- was set by a previous call to Get_First_Interp or Get_Next_Interp, the -- next interpretation is placed in It, and I is updated for the next call. -- The end of the list of interpretations is signalled by It.Nam = Empty. procedure Remove_Interp (I : in out Interp_Index); -- Remove an interpretation that is hidden by another, or that does not -- match the context. The value of I on input was set by a call to either -- Get_First_Interp or Get_Next_Interp and references the interpretation -- to be removed. The only allowed use of the exit value of I is as input -- to a subsequent call to Get_Next_Interp, which yields the interpretation -- following the removed one. procedure Save_Interps (Old_N : Node_Id; New_N : Node_Id); -- If an overloaded node is rewritten during semantic analysis, its -- possible interpretations must be linked to the copy. This procedure -- transfers the overload information (Is_Overloaded flag, and list of -- interpretations) from Old_N, the old node, to New_N, its new copy. -- It has no effect in the non-overloaded case. function Covers (T1, T2 : Entity_Id) return Boolean; -- This is the basic type compatibility routine. T1 is the expected type, -- imposed by context, and T2 is the actual type. The processing reflects -- both the definition of type coverage and the rules for operand matching; -- that is, this does not exactly match the RM definition of "covers". function Disambiguate (N : Node_Id; I1, I2 : Interp_Index; Typ : Entity_Id) return Interp; -- If more than one interpretation of a name in a call is legal, apply -- preference rules (universal types first) and operator visibility in -- order to remove ambiguity. I1 and I2 are the first two interpretations -- that are compatible with the context, but there may be others. function Entity_Matches_Spec (Old_S, New_S : Entity_Id) return Boolean; -- To resolve subprogram renaming and default formal subprograms in generic -- definitions. Old_S is a possible interpretation of the entity being -- renamed, New_S has an explicit signature. If Old_S is a subprogram, as -- opposed to an operator, type and mode conformance are required. function Find_Unique_Type (L : Node_Id; R : Node_Id) return Entity_Id; -- Used in second pass of resolution, for equality and comparison nodes. L -- is the left operand, whose type is known to be correct, and R is the -- right operand, which has one interpretation compatible with that of L. -- Return the type intersection of the two. function Has_Compatible_Type (N : Node_Id; Typ : Entity_Id) return Boolean; -- Verify that some interpretation of the node N has a type compatible with -- Typ. If N is not overloaded, then its unique type must be compatible -- with Typ. Otherwise iterate through the interpretations of N looking for -- a compatible one. function Hides_Op (F : Entity_Id; Op : Entity_Id) return Boolean; -- A user-defined function hides a predefined operator if it is matches the -- signature of the operator, and is declared in an open scope, or in the -- scope of the result type. function Interface_Present_In_Ancestor (Typ : Entity_Id; Iface : Entity_Id) return Boolean; -- Ada 2005 (AI-251): Typ must be a tagged record type/subtype and Iface -- must be an abstract interface type (or a class-wide abstract interface). -- This function is used to check if Typ or some ancestor of Typ implements -- Iface (returning True only if so). function Intersect_Types (L, R : Node_Id) return Entity_Id; -- Find the common interpretation to two analyzed nodes. If one of the -- interpretations is universal, choose the non-universal one. If either -- node is overloaded, find single common interpretation. function In_Generic_Actual (Exp : Node_Id) return Boolean; -- Determine whether the expression is part of a generic actual. At the -- time the actual is resolved the scope is already that of the instance, -- but conceptually the resolution of the actual takes place in the -- enclosing context and no special disambiguation rules should be applied. function Is_Ancestor (T1 : Entity_Id; T2 : Entity_Id; Use_Full_View : Boolean := False) return Boolean; -- T1 is a tagged type (not class-wide). Verify that it is one of the -- ancestors of type T2 (which may or not be class-wide). If Use_Full_View -- is True then the full-view of private parents is used when climbing -- through the parents of T2. -- -- Note: For analysis purposes the flag Use_Full_View must be set to False -- (otherwise we break the privacy contract since this routine returns true -- for hidden ancestors of private types). For expansion purposes this flag -- is generally set to True since the expander must know with precision the -- ancestors of a tagged type. For example, if a private type derives from -- an interface type then the interface may not be an ancestor of its full -- view since the full-view is only required to cover the interface (RM 7.3 -- (7.3/2))) and this knowledge affects construction of dispatch tables. function Is_Progenitor (Iface : Entity_Id; Typ : Entity_Id) return Boolean; -- Determine whether the interface Iface is implemented by Typ. It requires -- traversing the list of abstract interfaces of the type, as well as that -- of the ancestor types. The predicate is used to determine when a formal -- in the signature of an inherited operation must carry the derived type. function Is_Subtype_Of (T1 : Entity_Id; T2 : Entity_Id) return Boolean; -- Checks whether T1 is any subtype of T2 directly or indirectly. Applies -- only to scalar subtypes??? function Operator_Matches_Spec (Op, New_S : Entity_Id) return Boolean; -- Used to resolve subprograms renaming operators, and calls to user -- defined operators. Determines whether a given operator Op, matches -- a specification, New_S. procedure Set_Abstract_Op (I : Interp_Index; V : Entity_Id); -- Set the abstract operation field of an interpretation function Valid_Comparison_Arg (T : Entity_Id) return Boolean; -- A valid argument to an ordering operator must be a discrete type, a -- real type, or a one dimensional array with a discrete component type. function Valid_Boolean_Arg (T : Entity_Id) return Boolean; -- A valid argument of a boolean operator is either some boolean type, or a -- one-dimensional array of boolean type. procedure Write_Interp (It : Interp); -- Debugging procedure to display an Interp procedure Write_Interp_Ref (Map_Ptr : Int); -- Debugging procedure to display entry in Interp_Map. Would not be needed -- if it were possible to debug instantiations of Table. procedure Write_Overloads (N : Node_Id); -- Debugging procedure to output info on possibly overloaded entities for -- specified node. end Sem_Type;