Improve lambda case (#25)

* improve lambda case

correctly indent further cases for a lambda case expression where the first pattern is on the same line as `\case`

* add tests for lambda case on the same line

* update date of last change

* allow space between lambda and case

`\ case`, `\    case`, etc. are allowed in LambdaCase syntax.
Also update test to reflect this.

* include `-` in case pattern

* recognise literal string, character, list

Author: Futarimiti

indent/haskell.vim

@@ -2,7 +2,7 @@
 " Filename: indent/haskell.vim
 " Author: itchyny
 " License: MIT License
-" Last Change: 2023/11/07 19:40:39.
+" Last Change: 2024/08/04 15:46:49.
 " =============================================================================
 
 if exists('b:did_indent')
@@ -178,6 +178,10 @@ function! GetHaskellIndent() abort
     return match(line, '\v^\s*%(<where>|.*<let>)?\s*\zs') + &shiftwidth
   endif
 
+  if line =~# '\v\\\s*<case>\s*[[:alnum:](\-\"''\[]'
+    return match(line, '\v\\\s*<case>\s*\zs\S')
+  endif
+
   if nonblankline =~# '\v^.*[^|]\|[^|].*\='
     return s:after_guard()
   endif

test/case/lambda_case_literal.in.hs

@@ -0,0 +1,6 @@
+f = \case [] -> 0
+"one" -> 1
+'0':_ -> 0
+xs@('-':_) -> g $ read xs
+where g = \case -1 -> -100
+_ -> -1

test/case/lambda_case_literal.out.hs

@@ -0,0 +1,6 @@
+f = \case [] -> 0
+          "one" -> 1
+          '0':_ -> 0
+          xs@('-':_) -> g $ read xs
+  where g = \case -1 -> -100
+                  _ -> -1

test/case/lambda_case_same_line.in.hs

@@ -0,0 +1,5 @@
+f = \case 1 -> 0
+2 -> 1
+x -> g x
+where g = \ case  -1 -> -1
+_ -> 3

test/case/lambda_case_same_line.out.hs

@@ -0,0 +1,5 @@
+f = \case 1 -> 0
+          2 -> 1
+          x -> g x
+  where g = \ case  -1 -> -1
+                    _ -> 3