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227 lines
11 KiB
Racket
227 lines
11 KiB
Racket
#lang racket/base
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(require racket/match
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racket/list
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racket/generator
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(prefix-in lex: br-parser-tools/lex)
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brag/support
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brag/private/internal-support)
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(provide THE-ERROR-HANDLER
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make-permissive-tokenizer
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atomic-datum->syntax
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positions->srcloc
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rule-components->syntax
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remove-rule-name)
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;; The level of indirection here is necessary since the yacc grammar wants a
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;; function value for the error handler up front. We want to delay that decision
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;; till parse time.
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(define (THE-ERROR-HANDLER tok-ok? tok-name tok-value start-pos end-pos)
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(match (positions->srcloc start-pos end-pos)
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[(list src line col offset span)
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((current-parser-error-handler) tok-name
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tok-value
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offset
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line
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col
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span)]))
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(define no-position (lex:position #f #f #f))
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(define (no-position? p)
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(not
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(or (lex:position-line p)
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(lex:position-col p)
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(lex:position-offset p))))
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;; make-permissive-tokenizer: (U (sequenceof (U token token-struct eof void)) (-> (U token token-struct eof void))) hash -> (-> position-token)
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;; Creates a tokenizer from the given value.
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;; FIXME: clean up code.
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(define (make-permissive-tokenizer tokenizer token-type-hash)
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(define tokenizer-thunk (cond
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[(sequence? tokenizer)
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(sequence->generator tokenizer)]
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[(procedure? tokenizer)
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tokenizer]))
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;; lookup: symbol any pos pos -> position-token
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(define (lookup type val start-pos end-pos)
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(lex:position-token
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((hash-ref token-type-hash type
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(lambda ()
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((current-tokenizer-error-handler) (format "~a" type) val
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(lex:position-offset start-pos)
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(lex:position-line start-pos)
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(lex:position-col start-pos)
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(and (number? (lex:position-offset start-pos))
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(number? (lex:position-offset end-pos))
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(- (lex:position-offset end-pos)
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(lex:position-offset start-pos))))))
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val)
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start-pos end-pos))
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(define (permissive-tokenizer)
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(define next-token (tokenizer-thunk))
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(let loop ([next-token next-token][start no-position][end no-position])
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(match next-token
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[(or (? eof-object?) (? void?))
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(lookup 'EOF eof start end)]
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[(? symbol?)
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(lookup next-token next-token start end)]
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[(or (? string?) (? char?))
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(define next-token-str (format "~a" next-token))
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(lookup (string->symbol next-token-str) next-token-str start end)]
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;; Compatibility
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[(? lex:token?)
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(loop (token (lex:token-name next-token)
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(lex:token-value next-token)) start end)]
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[(token-struct type val offset line column span skip?)
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(cond [skip?
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;; skip whitespace, and just tokenize again.
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(permissive-tokenizer)]
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[(hash-has-key? token-type-hash type)
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(define start-pos (lex:position offset line column))
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;; try to synthesize a consistent end position.
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(define end-pos (lex:position (if (and (number? offset) (number? span))
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(+ offset span)
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offset)
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line
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(if (and (number? column) (number? span))
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(+ column span)
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column)))
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(lookup type val start-pos end-pos)]
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[else
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;; We ran into a token of unrecognized type. Let's raise an appropriate error.
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((current-tokenizer-error-handler) type val
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offset line column span)])]
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;; for the next two cases:
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;; carry the token's start and end position into the `a-position-token` recursion
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;; so that if an error arises, it's reported as coming from the location of the containing token
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[(lex:position-token t s e)
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(define a-position-token (loop t s e))
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(lex:position-token (lex:position-token-token a-position-token)
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(if (no-position? (lex:position-token-start-pos a-position-token))
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s
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(lex:position-token-start-pos a-position-token))
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(if (no-position? (lex:position-token-end-pos a-position-token))
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e
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(lex:position-token-end-pos a-position-token)))]
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[(lex:srcloc-token t loc)
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(define s (lex:position (srcloc-position loc) (srcloc-line loc) (srcloc-column loc)))
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(define e (lex:position (+ (srcloc-position loc) (srcloc-span loc)) #f #f))
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(define a-position-token (loop t s e))
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(lex:position-token (lex:position-token-token a-position-token)
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(if (no-position? (lex:position-token-start-pos a-position-token))
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s
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(lex:position-token-start-pos a-position-token))
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(if (no-position? (lex:position-token-start-pos a-position-token))
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e
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(lex:position-token-end-pos a-position-token)))]
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[else
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;; Otherwise, we have no idea how to treat this as a token.
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((current-tokenizer-error-handler) 'unknown-type (format "~a" next-token)
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#f #f #f #f)])))
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permissive-tokenizer)
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;; positions->srcloc: position position -> (list source line column offset span)
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;; Given two positions, returns a srcloc-like structure, where srcloc is the value
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;; consumed as the third argument to datum->syntax.
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(define (positions->srcloc start-pos end-pos)
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(list (current-source)
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(lex:position-line start-pos)
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(lex:position-col start-pos)
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(lex:position-offset start-pos)
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(if (and (number? (lex:position-offset end-pos))
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(number? (lex:position-offset start-pos)))
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(- (lex:position-offset end-pos)
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(lex:position-offset start-pos))
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#f)))
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#|
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MB: the next three functions control the parse tree output.
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This would be the place to check a syntax property for hiding.
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|#
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;; We create a syntax using read-syntax; by definition, it should have the
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;; original? property set to #t, which we then copy over to syntaxes constructed
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;; with atomic-datum->syntax and rule-components->syntax.
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(define stx-with-original?-property
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(read-syntax #f (open-input-string "meaningless-string")))
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;; atomic-datum->syntax: datum position position
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;; Helper that does the ugly work in wrapping a datum into a syntax
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;; with source location.
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(define (atomic-datum->syntax d start-pos end-pos)
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(datum->syntax #f d (positions->srcloc start-pos end-pos) stx-with-original?-property))
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(define (remove-rule-name component-stx #:splice? [splice #f])
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;; when removing a rule name, we apply it as a syntax property to the remaining elements
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;; for possible later usage (aka, why throw away information)
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(syntax-case component-stx ()
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[(name . subcomponents)
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(let ([name-datum (syntax->datum #'name)])
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;; two properties: 'rule returns name-datum, and name-datum returns original #'name stx
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(define (annotate-name stx) (syntax-property (syntax-property stx name-datum #'name) 'rule name-datum))
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(if splice
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;; when splicing, returned list is a regular list, with each element having the property.
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(map annotate-name (syntax->list #'subcomponents))
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;; when hiding, returned list should be a syntaxed list with the property
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;; iow, basically the same as `component-stx`, minus the name
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(annotate-name (datum->syntax component-stx #'subcomponents component-stx component-stx))))]
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[_ (raise-syntax-error 'remove-rule-name "component has no name" component-stx)]))
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(define (preprocess-component component-stx)
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(cond
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;; test splice first in case both hiding and splicing are set, for instance:
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;; /rule : thing @rule
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;; otherwise the hide prevents the splice from being expressed
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[(or (eq? (syntax-property component-stx 'hide-or-splice) 'splice)
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(syntax-property component-stx 'splice-rh-id))
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(remove-rule-name component-stx #:splice? #t)] ; spliced version is lifted out of the sublist
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[(eq? (syntax-property component-stx 'hide-or-splice) 'hide)
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(list (remove-rule-name component-stx))] ; hidden version still wrapped in a sublist
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[else (list component-stx)]))
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(define (preprocess-component-lists component-stxss)
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; "preprocess" means splicing and rule-name-hiding where indicated
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;; inside `component-stx` is a rule name followed by subcomponents
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(append*
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(for*/list ([component-stxs (in-list component-stxss)]
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[component-stx (in-list component-stxs)])
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(preprocess-component component-stx))))
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;; rule-components->syntax: (U symbol false) (listof stx) ... #:srcloc (U #f (list src line column offset span)) -> stx
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;; Creates an stx out of the rule name and its components.
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;; The location information of the rule spans that of its components.
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(define (rule-components->syntax rule-name/false #:srcloc [srcloc #f] #:hide-or-splice? [hide-or-splice #f] . component-lists)
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(define new-rule-name
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;; stash the hide property on rule names so we can use it later if we want
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(syntax-property (datum->syntax #f rule-name/false srcloc stx-with-original?-property) 'hide-or-splice? hide-or-splice))
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(define new-rule-components (preprocess-component-lists component-lists))
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(define rule-result (cons new-rule-name new-rule-components))
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(define syntaxed-rule-result (datum->syntax #f rule-result srcloc stx-with-original?-property))
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;; not 'hide-or-splice-lhs-id, because this will now become a (right-hand) component in a different (left-hand) rule
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;; actual splicing happens when the parent rule is processed (with procedure above)
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(syntax-property syntaxed-rule-result 'hide-or-splice hide-or-splice))
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