INTERFACE M3CScope;

This module implements scope checking. It assumes that it is to be used by a single threaded compiler working its way sequentially through the module being compiled.

The module provides several routines for handling the different constructs which introduce a new scope. When entering a new scope the compiler calls the appropriate routine in 'Enter' mode, causing 'M3CScope' to note the names introduced in that scope. On leaving the scope the same routine is called in 'Exit' mode, causing 'M3CScope' to forget the names introduced in that scope. Calls can be nested but each call in 'Enter' mode must be matched by a similar call in 'Exit' mode.

'M3CScope' provides the procedure 'Lookup', which can be called to find out the 'DEF_ID' currently associated with any identifer.

IMPORT M3AST_AS;

PROCEDURE Standard(standard: M3AST_AS.Compilation_Unit) RAISES {};

Must be called before any other procedure in the module in order to add the standard identifiers to the scope structures

TYPE
  Change = {Enter, Exit};

PROCEDURE CompilationUnit(
    cu: M3AST_AS.Compilation_Unit;
    change: Change)
    RAISES {};

Called at the beginning and end of scope checking for the given module. In enter mode: i) If the unit is a module notes all identifiers introduced into the scope due to exported interfaces. ii) Notes all identifiers introduced into the scope due to import statements. iii) Notes all the identifiers introduced into the scope due to top level declarations. Error messages are generated if the same identifier is introduced into the scope twice with different bindings, or if an identifier mentioned in a FROM .. IMPORT clause cannot be resolved. In exit mode this procedure forgets all identifiers introduced into the scope by the enter mode call

PROCEDURE Procedure(proc: M3AST_AS.Proc_decl; change: Change) RAISES {};

Called at the beginning and end of scope checking for the given procedure. In enter mode notes all the formal parameter identifiers and all the identifiers declared in the procedure body block. Error messages are generated if any of these names clash. In exit mode this procedure forgets all identifiers introduced into the scope by the enter mode call

PROCEDURE Method(meth: M3AST_AS.Method; change: Change) RAISES {};

Called at the beginning and end of scope checking for the given procedure. In enter mode notes all the formal parameter identifiers and all the identifiers declared in the procedure body block. Error messages are generated if any of these names clash. In exit mode this procedure forgets all identifiers introduced into the scope by the enter mode call

PROCEDURE Block(block: M3AST_AS.Block; change: Change) RAISES {};

Called at the beginning and end of scope checking for the given block. In enter mode notes all the identifiers declared in the block. Error messages are generated if any of these names clash. In exit mode this procedure forgets all identifiers introduced into the scope by the enter mode call. This procedure has no effect if called on a block which is the body of a procedure or compilation unit (because such blocks will have been taken care of by the corresponding 'CompilationUnit' or 'Procedure' call)

PROCEDURE DefId(defId: M3AST_AS.DEF_ID; change: Change) RAISES {};

Called at the beginning and end of a scope which introduces just one new identifier (e.g. a FOR statement). In enter mode notes the identifier, in exit mode forgets it

PROCEDURE Lookup(usedId: M3AST_AS.USED_ID) RAISES {};

Looks up 'usedId' in the current scope. If 'usedId' is bound to some item then 'usedId' is bound to the appropriate 'DEF_ID', otherwise an error message is given and 'usedId' is not changed (presumably leaving it unset). Note that multiple failed lookups of the same identifier may not cause multiple error messages. The implementation reserves the right to note that a certain 'identifier' is not declared and may issue just one error message, for the first failed lookup

END M3CScope.