;;;; An interpreting EVAL

;;;; 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!EVAL")

;; (declaim (optimize (speed 3) (debug 1) (safety 1)))

;;; Values used for marking specials/macros/etc in environments.
(defvar *special* (gensym "SPECIAL"))
(defvar *macro* (gensym "MACRO"))
(defvar *symbol-macro* (gensym "SYMBOL-MACRO"))
(defvar *not-present* (gensym "NOT-PRESENT"))

(define-condition interpreted-program-error (program-error simple-condition sb!impl::encapsulated-condition)
  ()
  (:report (lambda (condition stream)
             (if (slot-boundp condition 'condition)
                 (progn
                   (format stream "Error evaluating a form:~% ~A"
                           (sb!impl::encapsulated-condition condition)))
                 (format stream "Error evaluating a form:~% ~?"
                         (simple-condition-format-control condition)
                         (simple-condition-format-arguments condition))))))

;;; ANSI defines that program syntax errors should be of type
;;; PROGRAM-ERROR.  Therefore...
(define-condition arg-count-program-error (sb!kernel::arg-count-error
                                           program-error)
  ())

(defun arg-count-program-error (datum &rest arguments)
  (declare (ignore datum))
  (apply #'error 'arg-count-program-error arguments))

;; OAOOM? (see destructuring-bind.lisp)
(defmacro program-destructuring-bind (lambda-list arg-list &body body)
  (let ((arg-list-name (gensym "ARG-LIST-")))
    (multiple-value-bind (body local-decls)
        (sb!kernel:parse-defmacro lambda-list arg-list-name body nil
                                  'program-destructuring-bind
                                  :anonymousp t
                                  :doc-string-allowed nil
                                  :wrap-block nil
                                  :error-fun 'arg-count-program-error)
      `(let ((,arg-list-name ,arg-list))
         ,@local-decls
         ,body))))

(defun ip-error (format-control &rest format-arguments)
  (error 'interpreted-program-error
         :format-control format-control
         :format-arguments format-arguments))

(defmacro nconc-2 (a b)
  (let ((tmp (gensym))
        (tmp2 (gensym)))
    `(let ((,tmp ,a)
           (,tmp2 ,b))
       (if ,tmp
           (progn (setf (cdr (last ,tmp)) ,tmp2) ,tmp)
           ,tmp2))))

;;; Construct a compiler LEXENV from the same data that's used for
;;; creating an interpreter ENV. This is needed for example when
;;; passing the environment to macroexpanders or when compiling an
;;; interpreted function.
(defun fabricate-new-native-environment (old-lexenv new-funs new-expanders
                                         new-vars new-symbol-expansions
                                         declarations)
  (labels ((to-native-funs (binding)
             ;; Non-macroexpander function entries are irrelevant for
             ;; the LEXENV. If we're using the LEXENV for
             ;; macro-expansion any references to local non-macro
             ;; function bindings are undefined behaviour. If we're
             ;; compiling an interpreted function, a lexical environment
             ;; with non-macro functions will be too hairy to compile.
             (if (eq (cdr binding) *macro*)
                 (cons (car binding)
                       (cons 'sb!sys:macro
                             (cdr (assoc (car binding) new-expanders))))
                 (cons (car binding)
                       :bogus)))
           (to-native-vars (binding)
             ;; And likewise for symbol macros.
             (if (eq (cdr binding) *symbol-macro*)
                 (cons (car binding)
                       (cons 'sb!sys:macro
                             (cdr (assoc (car binding) new-symbol-expansions))))
                 (cons (car binding)
                       :bogus))))
    (let ((lexenv (sb!c::internal-make-lexenv
                   (nconc-2 (mapcar #'to-native-funs new-funs)
                            (sb!c::lexenv-funs old-lexenv))
                   (nconc-2 (mapcar #'to-native-vars new-vars)
                            (sb!c::lexenv-vars old-lexenv))
                   nil nil nil nil nil
                   (sb!c::lexenv-handled-conditions old-lexenv)
                   (sb!c::lexenv-disabled-package-locks old-lexenv)
                   (sb!c::lexenv-policy old-lexenv)
                   (sb!c::lexenv-user-data old-lexenv))))
      (dolist (declaration declarations)
        (unless (consp declaration)
          (ip-error "malformed declaration specifier ~S in ~S"
                    declaration (cons 'declare declarations)))
        (case (car declaration)
          ((optimize)
           (dolist (element (cdr declaration))
             (multiple-value-bind (quality value)
                 (if (not (consp element))
                     (values element 3)
                     (program-destructuring-bind (quality value)
                         element
                       (values quality value)))
               (if (sb!c::policy-quality-name-p quality)
                   (push (cons quality value)
                         (sb!c::lexenv-%policy lexenv))
                   (warn "ignoring unknown optimization quality ~
                                      ~S in ~S" quality
                                      (cons 'declare declarations))))))
          (sb!ext:muffle-conditions
           (setf (sb!c::lexenv-handled-conditions lexenv)
                 (sb!c::process-muffle-conditions-decl
                  declaration
                  (sb!c::lexenv-handled-conditions lexenv))))
          (sb!ext:unmuffle-conditions
           (setf (sb!c::lexenv-handled-conditions lexenv)
                 (sb!c::process-unmuffle-conditions-decl
                  declaration
                  (sb!c::lexenv-handled-conditions lexenv))))
          ((sb!ext:disable-package-locks sb!ext:enable-package-locks)
           (setf (sb!c::lexenv-disabled-package-locks lexenv)
                 (sb!c::process-package-lock-decl
                  declaration
                  (sb!c::lexenv-disabled-package-locks lexenv))))))
      lexenv)))

(defstruct (env
             (:constructor %make-env
                           (parent vars funs expanders symbol-expansions
                            tags blocks declarations native-lexenv)))
  parent
  vars
  funs
  expanders
  symbol-expansions
  tags
  blocks
  declarations
  native-lexenv)

(defun make-env (&key parent vars funs expanders
                 symbol-expansions tags blocks declarations)
  (%make-env parent
             (append vars (env-vars parent))
             (append funs (env-funs parent))
             (append expanders (env-expanders parent))
             (append symbol-expansions (env-symbol-expansions parent))
             (nconc-2 tags (env-tags parent))
             (nconc-2 blocks (env-blocks parent))
             declarations
             (fabricate-new-native-environment (env-native-lexenv parent)
                                               funs expanders
                                               vars symbol-expansions
                                               declarations)))

(defun make-null-environment ()
  (%make-env nil nil nil nil nil nil nil nil
             (sb!c::internal-make-lexenv
              nil nil
              nil nil nil nil nil nil nil
              sb!c::*policy*
              nil)))

;;; Augment ENV with a special or lexical variable binding
(declaim (inline push-var))
(defun push-var (name value env)
  (push (cons name value) (env-vars env))
  (push (cons name :bogus) (sb!c::lexenv-vars (env-native-lexenv env))))

;;; Augment ENV with a local function binding
(declaim (inline push-fun))
(defun push-fun (name value calling-env body-env)
  (when (fboundp name)
    (let ((sb!c:*lexenv* (env-native-lexenv calling-env)))
      (program-assert-symbol-home-package-unlocked
       :eval name "binding ~A as a local function")))
  (push (cons name value) (env-funs body-env))
  (push (cons name :bogus) (sb!c::lexenv-funs (env-native-lexenv body-env))))

(sb!int:def!method print-object ((env env) stream)
  (print-unreadable-object (env stream :type t :identity t)))

(macrolet ((define-get-binding (name accessor &key (test '#'eq))
             ;; A macro, sadly, because an inline function here is
             ;; "too hairy"
             `(defmacro ,name (symbol env)
                `(assoc ,symbol (,',accessor ,env) :test ,',test))))
  (define-get-binding get-binding env-vars)
  (define-get-binding get-fbinding env-funs :test #'equal)
  (define-get-binding get-expander-binding env-expanders)
  (define-get-binding get-symbol-expansion-binding env-symbol-expansions)
  (define-get-binding get-tag-binding env-tags :test #'eql)
  (define-get-binding get-block-binding env-blocks))

;;; Return a list of all symbols that are declared special in the
;;; declarations listen in DECLS.
(defun declared-specials (decls)
  (let ((specials nil))
    (dolist (decl decls)
      (when (eql (car decl) 'special)
        (dolist (var (cdr decl))
          (push var specials))))
    specials))

;;; Given a list of variables that should be marked as special in an
;;; environment, return the appropriate binding forms to be given
;;; to MAKE-ENV.
(defun special-bindings (specials env)
  (mapcar #'(lambda (var)
              (let ((sb!c:*lexenv* (env-native-lexenv env)))
                (program-assert-symbol-home-package-unlocked
                 :eval var "declaring ~A special"))
              (cons var *special*))
          specials))

;;; Return true if SYMBOL has been declared special either globally
;;; or is in the DECLARED-SPECIALS list.
(defun specialp (symbol declared-specials)
  (let ((type (sb!int:info :variable :kind symbol)))
    (cond
      ((eq type :constant)
       ;; Horrible place for this, but it works.
       (ip-error "Can't bind constant symbol: ~S" symbol))
      ((eq type :global)
       ;; Ditto...
       (ip-error "Can't bind a global variable: ~S" symbol))
      ((eq type :special) t)
      ((member symbol declared-specials :test #'eq)
       t)
      (t nil))))

(defun binding-name (binding)
  (if (consp binding) (first binding) binding))
(defun binding-value (binding)
  (if (consp binding) (second binding) nil))
(defun supplied-p-parameter (spec)
  (if (consp spec) (third spec) nil))
(defun keyword-name (spec)
  (if (consp spec)
      (if (consp (first spec))
          (second (first spec))
          (first spec))
      spec))
(defun keyword-key (spec)
  (if (consp spec)
      (if (consp (first spec))
          (first (first spec))
          (intern (symbol-name (first spec)) "KEYWORD"))
      (intern (symbol-name spec) "KEYWORD")))
(defun keyword-default-value (spec)
  (if (consp spec) (second spec) nil))

;;; Given a list of ARGUMENTS and a LAMBDA-LIST, return two values:
;;;   * An alist[*] mapping the required parameters of the function to
;;;     the corresponding argument values
;;;   * An alist mapping the keyword, optional and rest parameters of
;;;     the function to the corresponding argument values (if supplied)
;;;     or to the parameter's default expression (if not). Supplied-p
;;;     parameters and aux variables are handled in a similar manner.
;;;
;;; For example given the argument list of (1 2) and the lambda-list of
;;; (A &OPTIONAL (B A) (C (1+ A))), we'd return the values
;;; (A . '1) and ((B . '2) (C . (1+ A))).
;;;
;;; Used only for implementing calls to interpreted functions.
(defun parse-arguments (arguments lambda-list)
  (multiple-value-bind (required optional rest-p rest keyword-p
                        keyword allow-other-keys-p aux-p aux)
      (handler-bind ((style-warning #'muffle-warning))
        (sb!int:parse-lambda-list lambda-list))
    (let* ((original-arguments arguments)
           (arguments-present (length arguments))
           (required-length (length required))
           (optional-length (length optional))
           (non-keyword-arguments (+ required-length optional-length))
           (optionals-present (- (min non-keyword-arguments arguments-present)
                                 required-length))
           (keywords-present-p (> arguments-present non-keyword-arguments))
           (let-like-bindings nil)
           (let*-like-bindings nil))
      (cond
        ((< arguments-present required-length)
         (ip-error "~@<Too few arguments in ~S to satisfy lambda list ~S.~:@>"
                   arguments lambda-list))
        ((and (not (or rest-p keyword-p)) keywords-present-p)
         (ip-error "~@<Too many arguments in ~S to satisfy lambda list ~S.~:@>"
                   arguments lambda-list))
        ((and keyword-p keywords-present-p
              (oddp (- arguments-present non-keyword-arguments)))
         (ip-error "~@<Odd number of &KEY arguments in ~S for ~S.~:@>"
                   arguments lambda-list)))
      (dotimes (i required-length)
        (push (cons (pop required) (pop arguments)) let-like-bindings))
      (do ((optionals-parsed 0 (1+ optionals-parsed)))
          ((null optional))
        (let ((this-optional (pop optional))
              (supplied-p (< optionals-parsed optionals-present)))
          (push (cons (binding-name this-optional)
                      (if supplied-p
                          (list 'quote (pop arguments))
                          (binding-value this-optional)))
                let*-like-bindings)
          (when (supplied-p-parameter this-optional)
            (push (cons (supplied-p-parameter this-optional)
                        (list 'quote supplied-p))
                  let*-like-bindings))))
      (let ((keyword-plist arguments))
        (when rest-p
          (push (cons rest (list 'quote keyword-plist)) let*-like-bindings))
        (when keyword-p
          (unless (or allow-other-keys-p
                      (getf keyword-plist :allow-other-keys))
            (loop for (key value) on keyword-plist by #'cddr doing
                  (when (and (not (eq key :allow-other-keys))
                             (not (member key keyword :key #'keyword-key)))
                    (ip-error "~@<Unknown &KEY argument ~S in ~S for ~S.~:@>"
                              key original-arguments lambda-list))))
          (dolist (keyword-spec keyword)
            (let ((supplied (getf keyword-plist (keyword-key keyword-spec)
                                  *not-present*)))
              (push (cons (keyword-name keyword-spec)
                          (if (eq supplied *not-present*)
                              (keyword-default-value keyword-spec)
                              (list 'quote supplied)))
                    let*-like-bindings)
              (when (supplied-p-parameter keyword-spec)
                (push (cons (supplied-p-parameter keyword-spec)
                            (list 'quote (not (eq supplied *not-present*))))
                      let*-like-bindings))))))
      (when aux-p
        (do ()
            ((null aux))
          (let ((this-aux (pop aux)))
            (push (cons (binding-name this-aux)
                        (binding-value this-aux))
                  let*-like-bindings))))
      (values (nreverse let-like-bindings) (nreverse let*-like-bindings)))))

;;; Evaluate LET*-like (sequential) bindings.
;;;
;;; Given an alist of BINDINGS, evaluate the value form of the first
;;; binding in ENV, generate an augmented environment with a binding
;;; of the variable to the value in ENV, and then evaluate the next
;;; binding form. Once all binding forms have been handled, END-ACTION
;;; is funcalled with the final environment.
;;;
;;; SPECIALS is a list of variables that have a bound special declaration.
;;; These variables (and those that have been declaimed as special) are
;;; bound as special variables.
(defun eval-next-let*-binding (bindings specials env end-action)
  (flet ((maybe-eval (exp)
           ;; Pick off the easy (QUOTE x) case which is very common
           ;; due to function calls.  (see PARSE-ARGUMENTS)
           (if (and (consp exp) (eq (car exp) 'quote))
               (second exp)
               (%eval exp env))))
    (if bindings
        (let* ((binding-name (car (car bindings)))
               (binding-value (cdr (car bindings)))
               (new-env (make-env :parent env)))
          (if (specialp binding-name specials)
              (progv
                  (list binding-name)
                  (list (maybe-eval binding-value))
                ;; Mark the variable as special in this environment
                (push-var binding-name *special* new-env)
                (eval-next-let*-binding
                 (cdr bindings) specials new-env end-action))
              (progn
                (push-var binding-name (maybe-eval binding-value) new-env)
                (eval-next-let*-binding
                 (cdr bindings) specials new-env end-action))))
        (funcall end-action env))))

;;; Create a new environment based on OLD-ENV by adding the variable
;;; bindings in BINDINGS to it, and call FUNCTION with the new environment
;;; as the only parameter. DECLARATIONS are the declarations that were
;;; in a source position where bound declarations for the bindings could
;;; be introduced.
;;;
;;; FREE-SPECIALS-P controls whether all special declarations should
;;; end cause the variables to be marked as special in the environment
;;; (when true), or only bound declarations (when false). Basically
;;; it'll be T when handling a LET, and NIL when handling a call to an
;;; interpreted function.
(defun call-with-new-env (old-env bindings declarations
                          free-specials-p function)
  (let* ((specials (declared-specials declarations))
         (dynamic-vars nil)
         (dynamic-values nil))
    ;; To check for package-lock violations
    (special-bindings specials old-env)
    (flet ((generate-binding (binding)
             (if (specialp (car binding) specials)
                 ;; If the variable being bound is globally special or
                 ;; there's a bound special declaration for it, record it
                 ;; in DYNAMIC-VARS / -VALUES separately:
                 ;;   * To handle the case of FREE-SPECIALS-P == T more
                 ;;     cleanly.
                 ;;   * The dynamic variables will be bound with PROGV just
                 ;;     before funcalling
                 (progn
                   (push (car binding) dynamic-vars)
                   (push (cdr binding) dynamic-values)
                   nil)
                 ;; Otherwise it's a lexical binding, and the value
                 ;; will be recorded in the environment.
                 (list binding))))
      (let ((new-env (make-env
                      :parent old-env
                      :vars (mapcan #'generate-binding bindings)
                      :declarations declarations)))
        (dolist (special (if free-specials-p specials dynamic-vars))
          (push-var special *special* new-env))
        (if dynamic-vars
            (progv dynamic-vars dynamic-values
              (funcall function new-env))
            ;; When there are no specials, the PROGV would be a no-op,
            ;; but it's better to elide it completely, since the
            ;; funcall is then in tail position.
            (funcall function new-env))))))

;;; Create a new environment based on OLD-ENV by binding the argument
;;; list ARGUMENTS to LAMBDA-LIST, and call FUNCTION with the new
;;; environment as argument. DECLARATIONS are the declarations that
;;; were in a source position where bound declarations for the
;;; bindings could be introduced.
(defun call-with-new-env-full-parsing
    (old-env lambda-list arguments declarations function)
  (multiple-value-bind (let-like-bindings let*-like-binding)
      (parse-arguments arguments lambda-list)
    (let ((specials (declared-specials declarations))
          var-specials free-specials)
      ;; Separate the bound and free special declarations
      (dolist (special specials)
        (if (or (member special let-like-bindings :key #'car)
                (member special let*-like-binding :key #'car))
            (push special var-specials)
            (push special free-specials)))
      ;; First introduce the required parameters into the environment
      ;; with CALL-WITH-NEW-ENV
      (call-with-new-env
       old-env let-like-bindings declarations nil
       #'(lambda (env)
           ;; Then deal with optionals / keywords / etc.
           (eval-next-let*-binding
            let*-like-binding var-specials env
            #'(lambda (env)
                ;; And now that we have evaluated all the
                ;; initialization forms for the bindings, add the free
                ;; special declarations to the environment. To see why
                ;; this is the right thing to do (instead of passing
                ;; FREE-SPECIALS-P == T to CALL-WITH-NEW-ENV),
                ;; consider:
                ;;
                ;;   (eval '(let ((*a* 1))
                ;;     (declare (special *a*))
                ;;     (let ((*a* 2))
                ;;       (funcall (lambda (&optional (b *a*))
                ;;                  (declare (special *a*))
                ;;                  (values b *a*))))))
                ;;
                ;; *A* should be special in the body of the lambda, but
                ;; not when evaluating the default value of B.
                (dolist (special free-specials)
                  (push-var special *special* env))
                (funcall function env))))))))

;;; Set the VALUE of the binding (either lexical or special) of the
;;; variable named by SYMBOL in the environment ENV.
(defun set-variable (symbol value env)
  (let ((binding (get-binding symbol env)))
    (if binding
        (cond
          ((eq (cdr binding) *special*)
           (setf (symbol-value symbol) value))
          ((eq (cdr binding) *symbol-macro*)
           (error "Tried to set a symbol-macrolet!"))
          (t (setf (cdr binding) value)))
        (case (sb!int:info :variable :kind symbol)
          (:macro (error "Tried to set a symbol-macrolet!"))
          (:alien (let ((type (sb!int:info :variable :alien-info symbol)))
                    (setf (sb!alien::%heap-alien type) value)))
          (t
           (let ((type (sb!c::info :variable :type symbol)))
             (when type
               (let ((type-specifier (sb!kernel:type-specifier type)))
                 (unless (typep value type-specifier)
                   (error 'type-error
                          :datum value
                          :expected-type type-specifier))))
             (setf (symbol-value symbol) value)))))))

;;; Retrieve the value of the binding (either lexical or special) of
;;; the variable named by SYMBOL in the environment ENV. For symbol
;;; macros the expansion is returned instead.
(defun get-variable (symbol env)
  (let ((binding (get-binding symbol env)))
    (if binding
        (cond
          ((eq (cdr binding) *special*)
           (values (symbol-value symbol) :variable))
          ((eq (cdr binding) *symbol-macro*)
           (values (cdr (get-symbol-expansion-binding symbol env))
                   :expansion))
          (t (values (cdr binding) :variable)))
        (case (sb!int:info :variable :kind symbol)
          (:macro (values (macroexpand-1 symbol) :expansion))
          (:alien (values (sb!alien-internals:alien-value symbol) :variable))
          (t (values (symbol-value symbol) :variable))))))

;;; Retrieve the function/macro binding of the symbol NAME in
;;; environment ENV. The second return value will be :MACRO for macro
;;; bindings, :FUNCTION for function bindings.
(defun get-function (name env)
  (let ((binding (get-fbinding name env)))
    (if binding
        (cond
          ((eq (cdr binding) *macro*)
           (values (cdr (get-expander-binding name env)) :macro))
          (t (values (cdr binding) :function)))
        (cond
          ((and (symbolp name) (macro-function name))
           (values (macro-function name) :macro))
          (t (values (%coerce-name-to-fun name) :function))))))

;;; Return true if EXP is a lambda form.
(defun lambdap (exp)
  (case (car exp)
    ((lambda sb!int:named-lambda) t)))

;;; Split off the declarations (and the docstring, if
;;; DOC-STRING-ALLOWED is true) from the actual forms of BODY.
;;; Returns three values: the cons in BODY containing the first
;;; non-header subform, the docstring, and a list of the declarations.
;;;
;;; FIXME: The name of this function is somewhat misleading. It's not
;;; used just for parsing the headers from lambda bodies, but for all
;;; special forms that have attached declarations.
(defun parse-lambda-headers (body &key doc-string-allowed)
  (loop with documentation = nil
        with declarations = nil
        for form on body do
        (cond
          ((and doc-string-allowed (stringp (car form)))
           (if (cdr form)               ; CLHS 3.4.11
               (if documentation
                   (ip-error "~@<Duplicate doc string ~S.~:@>" (car form))
                   (setf documentation (car form)))
               (return (values form documentation declarations))))
          ((and (consp (car form)) (eql (caar form) 'declare))
           (setf declarations (append declarations (cdar form))))
          (t (return (values form documentation declarations))))
        finally (return (values nil documentation declarations))))

;;; Create an interpreted function from the lambda-form EXP evaluated
;;; in the environment ENV.
(defun eval-lambda (exp env)
  (case (car exp)
    ((lambda)
     (multiple-value-bind (body documentation declarations)
         (parse-lambda-headers (cddr exp) :doc-string-allowed t)
       (make-interpreted-function :lambda-list (second exp)
                                  :env env :body body
                                  :documentation documentation
                                  :source-location (sb!c::make-definition-source-location)
                                  :declarations declarations)))
    ((sb!int:named-lambda)
     (multiple-value-bind (body documentation declarations)
         (parse-lambda-headers (cdddr exp) :doc-string-allowed t)
       (make-interpreted-function :name (second exp)
                                  :lambda-list (third exp)
                                  :env env :body body
                                  :documentation documentation
                                  :source-location (sb!c::make-definition-source-location)
                                  :declarations declarations)))))

(defun eval-progn (body env)
  (let ((previous-exp nil))
    (dolist (exp body)
      (if previous-exp
          (%eval previous-exp env))
      (setf previous-exp exp))
    ;; Preserve tail call
    (%eval previous-exp env)))

(defun eval-if (body env)
  (program-destructuring-bind (test if-true &optional if-false) body
    (if (%eval test env)
        (%eval if-true env)
        (%eval if-false env))))

(defun eval-let (body env)
  (program-destructuring-bind (bindings &body body) body
    ;; First evaluate the bindings in parallel
    (let ((bindings (mapcar
                     #'(lambda (binding)
                         (cons (binding-name binding)
                               (%eval (binding-value binding) env)))
                     bindings)))
      (multiple-value-bind (body documentation declarations)
          (parse-lambda-headers body :doc-string-allowed nil)
        (declare (ignore documentation))
        ;; Then establish them into the environment, and evaluate the
        ;; body.
        (call-with-new-env env bindings declarations t
                           #'(lambda (env)
                               (eval-progn body env)))))))

(defun eval-let* (body old-env)
  (program-destructuring-bind (bindings &body body) body
    (multiple-value-bind (body documentation declarations)
        (parse-lambda-headers body :doc-string-allowed nil)
      (declare (ignore documentation))
      ;; First we separate the special declarations into bound and
      ;; free declarations.
      (let ((specials (declared-specials declarations))
            var-specials free-specials)
        (dolist (special specials)
          (if (member special bindings :key #'binding-name)
              (push special var-specials)
              (push special free-specials)))
        (let ((env (make-env :parent old-env
                             :declarations declarations)))
          ;; Then we establish the bindings into the environment
          ;; sequentially.
          (eval-next-let*-binding
           (mapcar #'(lambda (binding)
                       (cons (binding-name binding)
                             (binding-value binding)))
                   bindings)
           var-specials env
           #'(lambda (env)
               ;; Now that we're done evaluating the bindings, add the
               ;; free special declarations. See also
               ;; CALL-WITH-NEW-ENV-FULL-PARSING.
               (dolist (special free-specials)
                 (push-var special *special* env))
               (eval-progn body env))))))))

;; Return a named local function in the environment ENV, made from the
;; definition form FUNCTION-DEF.
(defun eval-local-function-def (function-def env)
  (program-destructuring-bind (name lambda-list &body local-body) function-def
    (multiple-value-bind (local-body documentation declarations)
        (parse-lambda-headers local-body :doc-string-allowed t)
      (%eval `#'(sb!int:named-lambda ,name ,lambda-list
                  ,@(if documentation
                        (list documentation)
                        nil)
                  (declare ,@declarations)
                  (block ,(cond ((consp name) (second name))
                                (t name))
                    ,@local-body))
             env))))

(defun eval-flet (body env)
  (program-destructuring-bind ((&rest local-functions) &body body) body
    (multiple-value-bind (body documentation declarations)
        (parse-lambda-headers body :doc-string-allowed nil)
      (declare (ignore documentation))
      (let* ((specials (declared-specials declarations))
             (new-env (make-env :parent env
                                :vars (special-bindings specials env)
                                :declarations declarations)))
        (dolist (function-def local-functions)
          (push-fun (car function-def)
                    ;; Evaluate the function definitions in ENV.
                    (eval-local-function-def function-def env)
                    ;; Do package-lock checks in ENV.
                    env
                    ;; But add the bindings to the child environment.
                    new-env))
        (eval-progn body new-env)))))

(defun eval-labels (body old-env)
  (program-destructuring-bind ((&rest local-functions) &body body) body
    (multiple-value-bind (body documentation declarations)
        (parse-lambda-headers body :doc-string-allowed nil)
      (declare (ignore documentation))
      ;; Create a child environment, evaluate the function definitions
      ;; in it, and add them into the same environment.
      (let ((env (make-env :parent old-env
                           :declarations declarations)))
        (dolist (function-def local-functions)
          (push-fun (car function-def)
                    (eval-local-function-def function-def env)
                    old-env
                    env))
        ;; And then add an environment for the body of the LABELS.  A
        ;; separate environment from the one where we added the
        ;; functions to is needed, since any special variable
        ;; declarations need to be in effect in the body, but not in
        ;; the bodies of the local functions.
        (let* ((specials (declared-specials declarations))
               (new-env (make-env :parent env
                                  :vars (special-bindings specials env))))
          (eval-progn body new-env))))))

;; Return a local macro-expander in the environment ENV, made from the
;; definition form FUNCTION-DEF.
(defun eval-local-macro-def (function-def env)
  (program-destructuring-bind (name lambda-list &body local-body) function-def
    (multiple-value-bind (local-body documentation declarations)
        (parse-lambda-headers local-body :doc-string-allowed t)
      ;; HAS-ENVIRONMENT and HAS-WHOLE will be either NIL or the name
      ;; of the variable. (Better names?)
      (let (has-environment has-whole)
        ;; Filter out &WHOLE and &ENVIRONMENT from the lambda-list, and
        ;; do some syntax checking.
        (when (eq (car lambda-list) '&whole)
          (setf has-whole (second lambda-list))
          (setf lambda-list (cddr lambda-list)))
        (setf lambda-list
              (loop with skip = 0
                    for element in lambda-list
                    if (cond
                         ((/= skip 0)
                          (decf skip)
                          (setf has-environment element)
                          nil)
                         ((eq element '&environment)
                          (if has-environment
                              (ip-error "Repeated &ENVIRONMENT.")
                              (setf skip 1))
                          nil)
                         ((eq element '&whole)
                          (ip-error "&WHOLE may only appear first ~
                                     in MACROLET lambda-list."))
                         (t t))
                    collect element))
        (let ((outer-whole (gensym "WHOLE"))
              (environment (or has-environment (gensym "ENVIRONMENT")))
              (macro-name (gensym "NAME")))
          (%eval `#'(lambda (,outer-whole ,environment)
                      ,@(if documentation
                            (list documentation)
                            nil)
                      (declare ,@(unless has-environment
                                         `((ignore ,environment))))
                      (program-destructuring-bind
                          (,@(if has-whole
                                 (list '&whole has-whole)
                                 nil)
                             ,macro-name ,@lambda-list)
                          ,outer-whole
                        (declare (ignore ,macro-name)
                                 ,@declarations)
                        (block ,name ,@local-body)))
                 env))))))

(defun eval-macrolet (body env)
  (program-destructuring-bind ((&rest local-functions) &body body) body
    (flet ((generate-fbinding (macro-def)
             (cons (car macro-def) *macro*))
           (generate-mbinding (macro-def)
             (let ((name (car macro-def))
                   (sb!c:*lexenv* (env-native-lexenv env)))
               (when (fboundp name)
                 (program-assert-symbol-home-package-unlocked
                  :eval name "binding ~A as a local macro"))
               (cons name (eval-local-macro-def macro-def env)))))
      (multiple-value-bind (body documentation declarations)
          (parse-lambda-headers body :doc-string-allowed nil)
        (declare (ignore documentation))
        (let* ((specials (declared-specials declarations))
               (new-env (make-env :parent env
                                  :vars (special-bindings specials env)
                                  :funs (mapcar #'generate-fbinding
                                                local-functions)
                                  :expanders (mapcar #'generate-mbinding
                                                     local-functions)
                                  :declarations declarations)))
          (eval-progn body new-env))))))

(defun eval-symbol-macrolet (body env)
  (program-destructuring-bind ((&rest bindings) &body body) body
    (flet ((generate-binding (binding)
             (cons (car binding) *symbol-macro*))
           (generate-sm-binding (binding)
             (let ((name (car binding))
                   (sb!c:*lexenv* (env-native-lexenv env)))
               (when (or (boundp name)
                         (eq (sb!int:info :variable :kind name) :macro))
                 (program-assert-symbol-home-package-unlocked
                  :eval name "binding ~A as a local symbol-macro"))
               (cons name (second binding)))))
      (multiple-value-bind (body documentation declarations)
          (parse-lambda-headers body :doc-string-allowed nil)
        (declare (ignore documentation))
        (let ((specials (declared-specials declarations)))
          (dolist (binding bindings)
            (when (specialp (binding-name binding) specials)
              (ip-error "~@<Can't bind SYMBOL-MACROLET of special ~
                         variable ~S.~:@>"
                        (binding-name binding)))))
        (let* ((specials (declared-specials declarations))
               (new-env (make-env :parent env
                                  :vars (nconc-2 (mapcar #'generate-binding
                                                         bindings)
                                                 (special-bindings specials env))
                                  :symbol-expansions (mapcar
                                                      #'generate-sm-binding
                                                      bindings)
                                  :declarations declarations)))
          (eval-progn body new-env))))))

(defun eval-progv (body env)
  (program-destructuring-bind (vars vals &body body) body
    (progv (%eval vars env) (%eval vals env)
      (eval-progn body env))))

(defun eval-function (body env)
  (program-destructuring-bind (name) body
    (cond
      ;; LAMBDAP assumes that the argument is a cons, so we need the
      ;; initial symbol case, instead of relying on the fall-through
      ;; case that has the same function body.
      ((symbolp name) (nth-value 0 (get-function name env)))
      ((lambdap name) (eval-lambda name env))
      (t (nth-value 0 (get-function name env))))))

(defun eval-eval-when (body env)
  (program-destructuring-bind ((&rest situation) &body body) body
    ;; FIXME: check that SITUATION only contains valid situations
    (if (or (member :execute situation)
            (member 'eval situation))
        (eval-progn body env))))

(defun eval-quote (body env)
  (declare (ignore env))
  (program-destructuring-bind (object) body
    object))

(defun eval-setq (pairs env)
  (when (oddp (length pairs))
    (ip-error "~@<Odd number of args to SETQ: ~S~:@>" (cons 'setq pairs)))
  (let ((last nil))
    (loop for (var new-val) on pairs by #'cddr do
          (handler-case
              (multiple-value-bind (expansion type) (get-variable var env)
                (ecase type
                  (:expansion
                   (setf last
                         (%eval (list 'setf expansion new-val) env)))
                  (:variable
                   (setf last (set-variable var (%eval new-val env)
                                            env)))))
            (unbound-variable (c)
              (declare (ignore c))
              (setf last (setf (symbol-value var)
                               (%eval new-val env))))))
    last))

(defun eval-multiple-value-call (body env)
  (program-destructuring-bind (function-form &body forms) body
    (%apply (%eval function-form env)
            (loop for form in forms
                  nconc (multiple-value-list (%eval form env))))))

(defun eval-multiple-value-prog1 (body env)
  (program-destructuring-bind (first-form &body forms) body
    (multiple-value-prog1 (%eval first-form env)
      (eval-progn forms env))))

(defun eval-catch (body env)
  (program-destructuring-bind (tag &body forms) body
    (catch (%eval tag env)
      (eval-progn forms env))))

(defun eval-tagbody (body old-env)
  (let ((env (make-env :parent old-env))
        (tags nil)
        (start body)
        (target-tag nil))
    (tagbody
       (flet ((go-to-tag (tag)
                (setf target-tag tag)
                (go go-to-tag)))
         ;; For each tag, store a trampoline function into the environment
         ;; and the location in the body into the TAGS alist.
         (do ((form body (cdr form)))
             ((null form) nil)
           (when (atom (car form))
             (when (assoc (car form) tags)
               (ip-error "The tag :A appears more than once in a tagbody."))
             (push (cons (car form) (cdr form)) tags)
             (push (cons (car form) #'go-to-tag) (env-tags env)))))
       ;; And then evaluate the forms in the body, starting from the
       ;; first one.
       (go execute)
     go-to-tag
       ;; The trampoline has set the TARGET-TAG. Restart evaluation of
       ;; the body from the location in body that matches the tag.
       (setf start (cdr (assoc target-tag tags)))
     execute
       (dolist (form start)
         (when (not (atom form))
           (%eval form env))))))

(defun eval-go (body env)
  (program-destructuring-bind (tag) body
    (let ((target (get-tag-binding tag env)))
      (if target
          ;; Call the GO-TO-TAG trampoline
          (funcall (cdr target) tag)
          (ip-error "~@<Attempt to GO to nonexistent tag: ~S~:@>" tag)))))

(defun eval-block (body old-env)
  (flet ((return-from-eval-block (&rest values)
           (return-from eval-block (values-list values))))
    (program-destructuring-bind (name &body body) body
      (unless (symbolp name)
        (ip-error "~@<The block name ~S is not a symbol.~:@>" name))
      (let ((env (make-env
                  :blocks (list (cons name #'return-from-eval-block))
                  :parent old-env)))
        (eval-progn body env)))))

(defun eval-return-from (body env)
  (program-destructuring-bind (name &optional result) body
    (let ((target (get-block-binding name env)))
      (if target
          (multiple-value-call (cdr target) (%eval result env))
          (ip-error "~@<Return for unknown block: ~S~:@>" name)))))

(defun eval-the (body env)
  (program-destructuring-bind (value-type form) body
    (declare (ignore value-type))
    ;; FIXME: We should probably check the types here, even though
    ;; the consequences of the values not being of the asserted types
    ;; are formally undefined.
    (%eval form env)))

(defun eval-unwind-protect (body env)
  (program-destructuring-bind (protected-form &body cleanup-forms) body
    (unwind-protect (%eval protected-form env)
      (eval-progn cleanup-forms env))))

(defun eval-throw (body env)
  (program-destructuring-bind (tag result-form) body
    (throw (%eval tag env)
      (%eval result-form env))))

(defun eval-load-time-value (body env)
  (program-destructuring-bind (form &optional read-only-p) body
    (declare (ignore read-only-p))
    (%eval form env)))

(defun eval-locally (body env)
  (multiple-value-bind (body documentation declarations)
      (parse-lambda-headers body :doc-string-allowed nil)
    (declare (ignore documentation))
    (let* ((specials (declared-specials declarations))
           (new-env (if (or specials declarations)
                        (make-env :parent env
                                  :vars (special-bindings specials env)
                                  :declarations declarations)
                        env)))
      (eval-progn body new-env))))

(defun eval-args (args env)
  (mapcar #'(lambda (arg) (%eval arg env)) args))

;;; The expansion of SB-SYS:WITH-PINNED-OBJECTS on GENCGC uses some
;;; VOPs which can't be reasonably implemented in the interpreter. So
;;; we special-case the macro.
(defun eval-with-pinned-objects (args env)
  (program-destructuring-bind (values &body body) args
    (if (null values)
        (eval-progn body env)
        (sb!sys:with-pinned-objects ((car values))
          (eval-with-pinned-objects (cons (cdr values) body) env)))))

(define-condition macroexpand-hook-type-error (type-error)
  ()
  (:report (lambda (condition stream)
             (format stream "The value of *MACROEXPAND-HOOK* is not a designator for a compiled function: ~A"
                     (type-error-datum condition)))))

(defvar *eval-dispatch-functions* nil)

;;; Dispatch to the appropriate EVAL-FOO function based on the contents of EXP.
(declaim (inline %%eval))
(defun %%eval (exp env)
  (cond
    ((symbolp exp)
     ;; CLHS 3.1.2.1.1 Symbols as Forms
     (multiple-value-bind (value kind) (get-variable exp env)
       (ecase kind
         (:variable value)
         (:expansion (%eval value env)))))
    ;; CLHS 3.1.2.1.3 Self-Evaluating Objects
    ((atom exp) exp)
    ;; CLHS 3.1.2.1.2 Conses as Forms
    ((consp exp)
     (case (car exp)
       ;; CLHS 3.1.2.1.2.1 Special Forms
       ((block)                (eval-block (cdr exp) env))
       ((catch)                (eval-catch (cdr exp) env))
       ((eval-when)            (eval-eval-when (cdr exp) env))
       ((flet)                 (eval-flet (cdr exp) env))
       ((function)             (eval-function (cdr exp) env))
       ((go)                   (eval-go (cdr exp) env))
       ((if)                   (eval-if (cdr exp) env))
       ((labels)               (eval-labels (cdr exp) env))
       ((let)                  (eval-let (cdr exp) env))
       ((let*)                 (eval-let* (cdr exp) env))
       ((load-time-value)      (eval-load-time-value (cdr exp) env))
       ((locally)              (eval-locally (cdr exp) env))
       ((macrolet)             (eval-macrolet (cdr exp) env))
       ((multiple-value-call)  (eval-multiple-value-call (cdr exp) env))
       ((multiple-value-prog1) (eval-multiple-value-prog1 (cdr exp) env))
       ((progn)                (eval-progn (cdr exp) env))
       ((progv)                (eval-progv (cdr exp) env))
       ((quote)                (eval-quote (cdr exp) env))
       ((return-from)          (eval-return-from (cdr exp) env))
       ((setq)                 (eval-setq (cdr exp) env))
       ((symbol-macrolet)      (eval-symbol-macrolet (cdr exp) env))
       ((tagbody)              (eval-tagbody (cdr exp) env))
       ((the)                  (eval-the (cdr exp) env))
       ((throw)                (eval-throw (cdr exp) env))
       ((unwind-protect)       (eval-unwind-protect (cdr exp) env))
       ;; SBCL-specific:
       ((sb!ext:truly-the)     (eval-the (cdr exp) env))
       ;; Not a special form, but a macro whose expansion wouldn't be
       ;; handled correctly by the evaluator.
       ((sb!sys:with-pinned-objects) (eval-with-pinned-objects (cdr exp) env))
       (t
        (let ((dispatcher (getf *eval-dispatch-functions* (car exp))))
          (cond
            (dispatcher
             (funcall dispatcher exp env))
            ;; CLHS 3.1.2.1.2.4 Lambda Forms
            ((and (consp (car exp)) (eq (caar exp) 'lambda))
             (interpreted-apply (eval-function (list (car exp)) env)
                                (eval-args (cdr exp) env)))
            (t
             (multiple-value-bind (function kind) (get-function (car exp) env)
               (ecase kind
                 ;; CLHS 3.1.2.1.2.3 Function Forms
                 (:function (%apply function (eval-args (cdr exp) env)))
                 ;; CLHS 3.1.2.1.2.2 Macro Forms
                 (:macro
                  (let ((hook *macroexpand-hook*))
                    ;; Having an interpreted function as the
                    ;; macroexpander hook could cause an infinite
                    ;; loop.
                    (unless (compiled-function-p
                             (etypecase hook
                               (function hook)
                               (symbol (symbol-function hook))))
                      (error 'macroexpand-hook-type-error
                             :datum hook
                             :expected-type 'compiled-function))
                    (%eval (funcall hook
                                    function
                                    exp
                                    (env-native-lexenv env))
                           env)))))))))))))

(defun %eval (exp env)
  (incf *eval-calls*)
  (if *eval-verbose*
      ;; Dynamically binding *EVAL-LEVEL* will prevent tail call
      ;; optimization. So only do it when its value will be used for
      ;; printing debug output.
      (let ((*eval-level* (1+ *eval-level*)))
        (let ((*print-circle* t))
          (format t "~&~vA~S~%" *eval-level* "" `(%eval ,exp)))
        (%%eval exp env))
      (%%eval exp env)))

(defun %apply (fun args)
  (etypecase fun
    (interpreted-function (interpreted-apply fun args))
    (function (apply fun args))
    (symbol (apply fun args))))

(defun interpreted-apply (fun args)
  (let ((lambda-list (interpreted-function-lambda-list fun))
        (env (interpreted-function-env fun))
        (body (interpreted-function-body fun))
        (declarations (interpreted-function-declarations fun)))
    (call-with-new-env-full-parsing
     env lambda-list args declarations
     #'(lambda (env)
         (eval-progn body env)))))

;;; We need separate conditions for the different *-TOO-COMPLEX-ERRORs to
;;; avoid spuriously triggering the handler in EVAL-IN-NATIVE-ENVIRONMENT
;;; on code like:
;;;
;;;   (let ((sb-ext:*evaluator-mode* :interpret))
;;;     (let ((fun (eval '(let ((a 1)) (lambda () a)))))
;;;         (eval `(compile nil ,fun))))
;;;
;;; FIXME: should these be exported?
(define-condition interpreter-environment-too-complex-error (simple-error)
  ())
(define-condition compiler-environment-too-complex-error (simple-error)
  ())

;;; Try to compile an interpreted function. If the environment
;;; contains local functions or lexical variables we'll punt on
;;; compiling it.
(defun prepare-for-compile (function)
  (let ((env (interpreted-function-env function)))
    (when (or (env-tags env)
              (env-blocks env)
              (find-if-not #'(lambda (x) (eq x *macro*))
                           (env-funs env) :key #'cdr)
              (find-if-not #'(lambda (x) (eq x *symbol-macro*))
                           (env-vars env)
                           :key #'cdr))
      (error 'interpreter-environment-too-complex-error
             :format-control
             "~@<Lexical environment of ~S is too complex to compile.~:@>"
             :format-arguments
             (list function)))
    (values
     `(sb!int:named-lambda ,(interpreted-function-name function)
          ,(interpreted-function-lambda-list function)
        (declare ,@(interpreted-function-declarations function))
        ,@(interpreted-function-body function))
     (env-native-lexenv env))))

;;; Convert a compiler LEXENV to an interpreter ENV. This is needed
;;; for EVAL-IN-LEXENV.
(defun make-env-from-native-environment (lexenv)
  (let ((native-funs (sb!c::lexenv-funs lexenv))
        (native-vars (sb!c::lexenv-vars lexenv)))
    (flet ((is-macro (thing)
             (and (consp thing) (eq (car thing) 'sb!sys:macro))))
      (when (or (sb!c::lexenv-blocks lexenv)
                (sb!c::lexenv-cleanup lexenv)
                (sb!c::lexenv-lambda lexenv)
                (sb!c::lexenv-tags lexenv)
                (sb!c::lexenv-type-restrictions lexenv)
                (find-if-not #'is-macro native-funs :key #'cdr)
                (find-if-not #'is-macro native-vars :key #'cdr))
        (error 'compiler-environment-too-complex-error
               :format-control
               "~@<Lexical environment is too complex to evaluate in: ~S~:@>"
               :format-arguments
               (list lexenv))))
    (flet ((make-binding (native)
             (cons (car native) *symbol-macro*))
           (make-sm-binding (native)
             (cons (car native) (cddr native)))
           (make-fbinding (native)
             (cons (car native) *macro*))
           (make-mbinding (native)
             (cons (car native) (cddr native))))
      (%make-env nil
                 (mapcar #'make-binding native-vars)
                 (mapcar #'make-fbinding native-funs)
                 (mapcar #'make-mbinding native-funs)
                 (mapcar #'make-sm-binding native-vars)
                 nil
                 nil
                 nil
                 lexenv))))

(defun eval-in-environment (form env)
  (%eval form env))

(defun eval-in-native-environment (form lexenv)
  (handler-bind
      ((sb!impl::eval-error
         (lambda (condition)
           (error 'interpreted-program-error
                  :condition (sb!int:encapsulated-condition condition)
                  :form form))))
    (sb!c:with-compiler-error-resignalling
      (handler-case
          (let ((env (make-env-from-native-environment lexenv)))
            (%eval form env))
        (compiler-environment-too-complex-error (condition)
          (declare (ignore condition))
          (sb!int:style-warn 'sb!kernel:lexical-environment-too-complex
                             :form form :lexenv lexenv)
          (sb!int:simple-eval-in-lexenv form lexenv))))))