;;;; the representation of a lexical environment

;;;; This software is part of the SBCL system. See the README file for
;;;; more information.
;;;;
;;;; This software is derived from the CMU CL system, which was
;;;; written at Carnegie Mellon University and released into the
;;;; public domain. The software is in the public domain and is
;;;; provided with absolutely no warranty. See the COPYING and CREDITS
;;;; files for more information.

(in-package "SB!C")

#!-sb-fluid (declaim (inline internal-make-lexenv)) ; only called in one place

;;; The LEXENV represents the lexical environment used for IR1 conversion.
;;; (This is also what shows up as an ENVIRONMENT value in macroexpansion.)
#!-sb-fluid (declaim (inline internal-make-lexenv)) ; only called in one place
(def!struct (lexenv
	     ;; FIXME: should probably be called MAKE-EMPTY-LEXENV or
	     ;; MAKE-NULL-LEXENV
	     (:constructor make-null-lexenv ())
	     (:constructor internal-make-lexenv
			   (functions variables blocks tags type-restrictions
				      lambda cleanup policy options)))
  ;; Alist (NAME . WHAT), where WHAT is either a Functional (a local function),
  ;; a DEFINED-FUNCTION, representing an INLINE/NOTINLINE declaration, or
  ;; a list (MACRO . <function>) (a local macro, with the specifier
  ;; expander.) Note that NAME may be a (SETF <name>) function.
  (functions nil :type list)
  ;; an alist translating variable names to LEAF structures. A special
  ;; binding is indicated by a :SPECIAL GLOBAL-VAR leaf. Each special
  ;; binding within the code gets a distinct leaf structure, as does
  ;; the current "global" value on entry to the code compiled.
  ;; (locally (special ...)) is handled by adding the most recent
  ;; special binding to the front of the list.
  ;;
  ;; If the CDR is (MACRO . <exp>), then <exp> is the expansion of a
  ;; symbol macro.
  (variables nil :type list)
  ;; BLOCKS and TAGS are alists from block and go-tag names to 2-lists
  ;; of the form (<entry> <continuation>), where <continuation> is the
  ;; continuation to exit to, and <entry> is the corresponding ENTRY node.
  (blocks nil :type list)
  (tags nil :type list)
  ;; an alist (THING . CTYPE) which is used to keep track of
  ;; "pervasive" type declarations. When THING is a leaf, this is for
  ;; type declarations that pertain to the type in a syntactic extent
  ;; which does not correspond to a binding of the affected name. When
  ;; Thing is a continuation, this is used to track the innermost THE
  ;; type declaration.
  (type-restrictions nil :type list)
  ;; the lexically enclosing lambda, if any
  ;; 
  ;; FIXME: This should be :TYPE (OR CLAMBDA NULL), but it was too hard
  ;; to get CLAMBDA defined in time for the cross-compiler.
  (lambda nil) 
  ;; the lexically enclosing cleanup, or NIL if none enclosing within Lambda
  ;;
  ;; FIXME: This should be :TYPE (OR CLEANUP NULL), but it was too hard
  ;; to get CLEANUP defined in time for the cross-compiler.
  (cleanup nil)
  ;; the current OPTIMIZE policy
  (policy *policy* :type policy)
  ;; an alist of miscellaneous options that are associated with the
  ;; lexical environment
  (options nil :type list))