[nongnu] elpa/haskell-tng-mode 96609e4 052/385: thoughts on layout inference

[ELPA Syncer]

branch: elpa/haskell-tng-mode
commit 96609e4b9a4b8572c0527dde20657434dbabd4ac
Author: Tseen She <ts33n.sh3@gmail.com>
Commit: Tseen She <ts33n.sh3@gmail.com>

    thoughts on layout inference
---
 haskell-tng-smie.el        | 41 +++++++++++++++++++++++++++++------------
 test/lexer/layout.hs.lexer |  4 ++--
 2 files changed, 31 insertions(+), 14 deletions(-)

diff --git a/haskell-tng-smie.el b/haskell-tng-smie.el
index 576a783..67ac14d 100644
--- a/haskell-tng-smie.el
+++ b/haskell-tng-smie.el
@@ -46,17 +46,27 @@
             (case-fold-search nil)
             (syntax (char-syntax (char-after))))
         (cond
-         ;; TODO brace inference
-         ((and
-           (not (eq start-line this-line))
-           (<=
-            (haskell-tng-smie:indentation-level (point))
-            (haskell-tng-smie:indentation-level start))
-           ";"))
+         ;; layout: semicolon inference
+         ((not (eq start-line this-line))
+          (let ((start-layout (haskell-tng-smie:layout-level start-line))
+                (this-layout (current-indentation)))
+            (cond
+             ((null start-layout) ""
+              (eq start-layout this-layout) ";"
+              t ""))))
 
          ;; parens
          ((member syntax '(?\( ?\) ?\" ?$)) nil)
 
+         ;; TODO brace inference ("offside" rule).
+         ;;
+         ;; Starting braces are trivial, there is a known list of keywords, so
+         ;; we just need to do a lookback when we hit a non-{ lexeme. Ending
+         ;; braces are a lot harder, as we need to calculate "do we need to
+         ;; close a brace here" every time the indentation level decreases. A
+         ;; possible solution is to calculate and cache the closing brace when
+         ;; discovering an open brace, but that just introduces more problems.
+
          ;; regexps
          ((or
            ;; known identifiers
@@ -68,12 +78,19 @@
           (goto-char (match-end 0))
           (match-string-no-properties 0)))))))
 
-(defun haskell-tng-smie:indentation-level (p)
-  "Calculates the indentation level of the most inner part of the given 
point's line."
-  ;; FIXME this is a hack for now, look for `let', `do' and friends according 
to
-  ;; the Haskell2010 report.
+(defun haskell-tng-smie:layout-level (line)
+  "Calculates the layout indentation of the most inner part of
+the given point's line."
+  ;; FIXME should the input be the line numbers?
+  ;;
+  ;; TODO starting at the end of the line, look backwards for wldo (where, 
let, do, of).
+  ;; If the wldo is the last lexeme, then the layout level is set by the next 
line (return nil).
+  ;; If the wldo is followed by a non-brace lexeme, set the layout level.
+  ;;
+  ;; If there is no wldo, the layout level is set by the indentation level
+  ;; (think about this some more)
   (save-excursion
-    (goto-char p)
+    (goto-line line)
     (current-indentation)))
 
 ;; TODO a haskell grammar
diff --git a/test/lexer/layout.hs.lexer b/test/lexer/layout.hs.lexer
index d048eb2..f76687b 100644
--- a/test/lexer/layout.hs.lexer
+++ b/test/lexer/layout.hs.lexer
@@ -64,8 +64,8 @@ where
 stkToLst
 Empty
 =
-[
-]
+SYNTAX_[
+SYNTAX_]
 ;
 stkToLst
 SYNTAX_(