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+" Vim indent file
+" Language: Rust
+" Author: Chris Morgan <me@chrismorgan.info>
+" Last Change: 2023-09-11
+" For bugs, patches and license go to https://github.com/rust-lang/rust.vim
+
+" Only load this indent file when no other was loaded.
+if exists("b:did_indent")
+ finish
+endif
+let b:did_indent = 1
+
+setlocal cindent
+setlocal cinoptions=L0,(s,Ws,J1,j1,m1
+setlocal cinkeys=0{,0},!^F,o,O,0[,0],0(,0)
+" Don't think cinwords will actually do anything at all... never mind
+setlocal cinwords=for,if,else,while,loop,impl,mod,unsafe,trait,struct,enum,fn,extern,macro
+
+" Some preliminary settings
+setlocal nolisp " Make sure lisp indenting doesn't supersede us
+setlocal autoindent " indentexpr isn't much help otherwise
+" Also do indentkeys, otherwise # gets shoved to column 0 :-/
+setlocal indentkeys=0{,0},!^F,o,O,0[,0],0(,0)
+
+setlocal indentexpr=GetRustIndent(v:lnum)
+
+let b:undo_indent = "setlocal cindent< cinoptions< cinkeys< cinwords< lisp< autoindent< indentkeys< indentexpr<"
+
+" Only define the function once.
+if exists("*GetRustIndent")
+ finish
+endif
+
+" vint: -ProhibitAbbreviationOption
+let s:save_cpo = &cpo
+set cpo&vim
+" vint: +ProhibitAbbreviationOption
+
+" Come here when loading the script the first time.
+
+function! s:get_line_trimmed(lnum)
+ " Get the line and remove a trailing comment.
+ " Use syntax highlighting attributes when possible.
+ " NOTE: this is not accurate; /* */ or a line continuation could trick it
+ let line = getline(a:lnum)
+ let line_len = strlen(line)
+ if has('syntax_items')
+ " If the last character in the line is a comment, do a binary search for
+ " the start of the comment. synID() is slow, a linear search would take
+ " too long on a long line.
+ if synIDattr(synID(a:lnum, line_len, 1), "name") =~? 'Comment\|Todo'
+ let min = 1
+ let max = line_len
+ while min < max
+ let col = (min + max) / 2
+ if synIDattr(synID(a:lnum, col, 1), "name") =~? 'Comment\|Todo'
+ let max = col
+ else
+ let min = col + 1
+ endif
+ endwhile
+ let line = strpart(line, 0, min - 1)
+ endif
+ return substitute(line, "\s*$", "", "")
+ else
+ " Sorry, this is not complete, nor fully correct (e.g. string "//").
+ " Such is life.
+ return substitute(line, "\s*//.*$", "", "")
+ endif
+endfunction
+
+function! s:is_string_comment(lnum, col)
+ if has('syntax_items')
+ for id in synstack(a:lnum, a:col)
+ let synname = synIDattr(id, "name")
+ if synname ==# "rustString" || synname =~# "^rustComment"
+ return 1
+ endif
+ endfor
+ else
+ " without syntax, let's not even try
+ return 0
+ endif
+endfunction
+
+if exists('*shiftwidth')
+ function! s:shiftwidth()
+ return shiftwidth()
+ endfunc
+else
+ function! s:shiftwidth()
+ return &shiftwidth
+ endfunc
+endif
+
+function GetRustIndent(lnum)
+ " Starting assumption: cindent (called at the end) will do it right
+ " normally. We just want to fix up a few cases.
+
+ let line = getline(a:lnum)
+
+ if has('syntax_items')
+ let synname = synIDattr(synID(a:lnum, 1, 1), "name")
+ if synname ==# "rustString"
+ " If the start of the line is in a string, don't change the indent
+ return -1
+ elseif synname =~? '\(Comment\|Todo\)'
+ \ && line !~# '^\s*/\*' " not /* opening line
+ if synname =~? "CommentML" " multi-line
+ if line !~# '^\s*\*' && getline(a:lnum - 1) =~# '^\s*/\*'
+ " This is (hopefully) the line after a /*, and it has no
+ " leader, so the correct indentation is that of the
+ " previous line.
+ return GetRustIndent(a:lnum - 1)
+ endif
+ endif
+ " If it's in a comment, let cindent take care of it now. This is
+ " for cases like "/*" where the next line should start " * ", not
+ " "* " as the code below would otherwise cause for module scope
+ " Fun fact: " /*\n*\n*/" takes two calls to get right!
+ return cindent(a:lnum)
+ endif
+ endif
+
+ " cindent gets second and subsequent match patterns/struct members wrong,
+ " as it treats the comma as indicating an unfinished statement::
+ "
+ " match a {
+ " b => c,
+ " d => e,
+ " f => g,
+ " };
+
+ " Search backwards for the previous non-empty line.
+ let prevlinenum = prevnonblank(a:lnum - 1)
+ let prevline = s:get_line_trimmed(prevlinenum)
+ while prevlinenum > 1 && prevline !~# '[^[:blank:]]'
+ let prevlinenum = prevnonblank(prevlinenum - 1)
+ let prevline = s:get_line_trimmed(prevlinenum)
+ endwhile
+
+ " A standalone '{', '}', or 'where'
+ let l:standalone_open = line =~# '\V\^\s\*{\s\*\$'
+ let l:standalone_close = line =~# '\V\^\s\*}\s\*\$'
+ let l:standalone_where = line =~# '\V\^\s\*where\s\*\$'
+ if l:standalone_open || l:standalone_close || l:standalone_where
+ " ToDo: we can search for more items than 'fn' and 'if'.
+ let [l:found_line, l:col, l:submatch] =
+ \ searchpos('\<\(fn\)\|\(if\)\>', 'bnWp')
+ if l:found_line !=# 0
+ " Now we count the number of '{' and '}' in between the match
+ " locations and the current line (there is probably a better
+ " way to compute this).
+ let l:i = l:found_line
+ let l:search_line = strpart(getline(l:i), l:col - 1)
+ let l:opens = 0
+ let l:closes = 0
+ while l:i < a:lnum
+ let l:search_line2 = substitute(l:search_line, '\V{', '', 'g')
+ let l:opens += strlen(l:search_line) - strlen(l:search_line2)
+ let l:search_line3 = substitute(l:search_line2, '\V}', '', 'g')
+ let l:closes += strlen(l:search_line2) - strlen(l:search_line3)
+ let l:i += 1
+ let l:search_line = getline(l:i)
+ endwhile
+ if l:standalone_open || l:standalone_where
+ if l:opens ==# l:closes
+ return indent(l:found_line)
+ endif
+ else
+ " Expect to find just one more close than an open
+ if l:opens ==# l:closes + 1
+ return indent(l:found_line)
+ endif
+ endif
+ endif
+ endif
+
+ " A standalone 'where' adds a shift.
+ let l:standalone_prevline_where = prevline =~# '\V\^\s\*where\s\*\$'
+ if l:standalone_prevline_where
+ return indent(prevlinenum) + 4
+ endif
+
+ " Handle where clauses nicely: subsequent values should line up nicely.
+ if prevline[len(prevline) - 1] ==# ","
+ \ && prevline =~# '^\s*where\s'
+ return indent(prevlinenum) + 6
+ endif
+
+ let l:last_prevline_character = prevline[len(prevline) - 1]
+
+ " A line that ends with '.<expr>;' is probably an end of a long list
+ " of method operations.
+ if prevline =~# '\V\^\s\*.' && l:last_prevline_character ==# ';'
+ call cursor(a:lnum - 1, 1)
+ let l:scope_start = searchpair('{\|(', '', '}\|)', 'nbW',
+ \ 's:is_string_comment(line("."), col("."))')
+ if l:scope_start != 0 && l:scope_start < a:lnum
+ return indent(l:scope_start) + 4
+ endif
+ endif
+
+ if l:last_prevline_character ==# ","
+ \ && s:get_line_trimmed(a:lnum) !~# '^\s*[\[\]{})]'
+ \ && prevline !~# '^\s*fn\s'
+ \ && prevline !~# '([^()]\+,$'
+ \ && s:get_line_trimmed(a:lnum) !~# '^\s*\S\+\s*=>'
+ " Oh ho! The previous line ended in a comma! I bet cindent will try to
+ " take this too far... For now, let's normally use the previous line's
+ " indent.
+
+ " One case where this doesn't work out is where *this* line contains
+ " square or curly brackets; then we normally *do* want to be indenting
+ " further.
+ "
+ " Another case where we don't want to is one like a function
+ " definition with arguments spread over multiple lines:
+ "
+ " fn foo(baz: Baz,
+ " baz: Baz) // <-- cindent gets this right by itself
+ "
+ " Another case is similar to the previous, except calling a function
+ " instead of defining it, or any conditional expression that leaves
+ " an open paren:
+ "
+ " foo(baz,
+ " baz);
+ "
+ " if baz && (foo ||
+ " bar) {
+ "
+ " Another case is when the current line is a new match arm.
+ "
+ " There are probably other cases where we don't want to do this as
+ " well. Add them as needed.
+ return indent(prevlinenum)
+ endif
+
+ if !has("patch-7.4.355")
+ " cindent before 7.4.355 doesn't do the module scope well at all; e.g.::
+ "
+ " static FOO : &'static [bool] = [
+ " true,
+ " false,
+ " false,
+ " true,
+ " ];
+ "
+ " uh oh, next statement is indented further!
+
+ " Note that this does *not* apply the line continuation pattern properly;
+ " that's too hard to do correctly for my liking at present, so I'll just
+ " start with these two main cases (square brackets and not returning to
+ " column zero)
+
+ call cursor(a:lnum, 1)
+ if searchpair('{\|(', '', '}\|)', 'nbW',
+ \ 's:is_string_comment(line("."), col("."))') == 0
+ if searchpair('\[', '', '\]', 'nbW',
+ \ 's:is_string_comment(line("."), col("."))') == 0
+ " Global scope, should be zero
+ return 0
+ else
+ " At the module scope, inside square brackets only
+ "if getline(a:lnum)[0] == ']' || search('\[', '', '\]', 'nW') == a:lnum
+ if line =~# "^\\s*]"
+ " It's the closing line, dedent it
+ return 0
+ else
+ return &shiftwidth
+ endif
+ endif
+ endif
+ endif
+
+ " Fall back on cindent, which does it mostly right
+ return cindent(a:lnum)
+endfunction
+
+" vint: -ProhibitAbbreviationOption
+let &cpo = s:save_cpo
+unlet s:save_cpo
+" vint: +ProhibitAbbreviationOption
+
+" vim: set et sw=4 sts=4 ts=8: