Support lambda as function

[renkun-ken]

In R 4.1, lambda \(args) { ... } is introduced as a shortcut of function(args) { ... }.

fun1 <- function(var1, var2) {
  var1 + var2
}

fun2 <- \(var1, var2) {
  var1 + var2
}

but the parse data is only different at FUNCTION and \\\\:

> getParseData(e)                                                                                           
   line1 col1 line2 col2 id parent          token terminal     text
29     1    1     3    1 29      0           expr    FALSE         
1      1    1     1    4  1      3         SYMBOL     TRUE     fun1
3      1    1     1    4  3     29           expr    FALSE         
2      1    6     1    7  2     29    LEFT_ASSIGN     TRUE       <-
28     1    9     3    1 28     29           expr    FALSE         
4      1    9     1   16  4     28       FUNCTION     TRUE function
5      1   17     1   17  5     28            '('     TRUE        (
6      1   18     1   21  6     28 SYMBOL_FORMALS     TRUE     var1
7      1   22     1   22  7     28            ','     TRUE        ,
9      1   24     1   27  9     28 SYMBOL_FORMALS     TRUE     var2
10     1   28     1   28 10     28            ')'     TRUE        )
25     1   30     3    1 25     28           expr    FALSE         
12     1   30     1   30 12     25            '{'     TRUE        {
20     2    3     2   13 20     25           expr    FALSE         
14     2    3     2    6 14     16         SYMBOL     TRUE     var1
16     2    3     2    6 16     20           expr    FALSE         
15     2    8     2    8 15     20            '+'     TRUE        +
17     2   10     2   13 17     19         SYMBOL     TRUE     var2
19     2   10     2   13 19     20           expr    FALSE         
23     3    1     3    1 23     25            '}'     TRUE        }
62     5    1     7    1 62      0           expr    FALSE         
34     5    1     5    4 34     36         SYMBOL     TRUE     fun2
36     5    1     5    4 36     62           expr    FALSE         
35     5    6     5    7 35     62    LEFT_ASSIGN     TRUE       <-
61     5    9     7    1 61     62           expr    FALSE         
37     5    9     5    9 37     61         '\\\\'     TRUE       \\
38     5   10     5   10 38     61            '('     TRUE        (
39     5   11     5   14 39     61 SYMBOL_FORMALS     TRUE     var1
40     5   15     5   15 40     61            ','     TRUE        ,
42     5   17     5   20 42     61 SYMBOL_FORMALS     TRUE     var2
43     5   21     5   21 43     61            ')'     TRUE        )
58     5   23     7    1 58     61           expr    FALSE         
45     5   23     5   23 45     58            '{'     TRUE        {
53     6    3     6   13 53     58           expr    FALSE         
47     6    3     6    6 47     49         SYMBOL     TRUE     var1
49     6    3     6    6 49     53           expr    FALSE         
48     6    8     6    8 48     53            '+'     TRUE        +
50     6   10     6   13 50     52         SYMBOL     TRUE     var2
52     6   10     6   13 52     53           expr    FALSE         
56     7    1     7    1 56     58            '}'     TRUE        }

r-lib/xmlparsedata#18 also added support for OP-LAMBDA so that we could work with the XML parse data:

<?xml version="1.0" encoding="UTF-8" standalone="yes" ?>
<exprlist>
  <expr line1="1" col1="1" line2="3" col2="1" start="32" end="94">
    <expr line1="1" col1="1" line2="1" col2="4" start="32" end="35">
      <SYMBOL line1="1" col1="1" line2="1" col2="4" start="32" end="35">fun1</SYMBOL>
    </expr>
    <LEFT_ASSIGN line1="1" col1="6" line2="1" col2="7" start="37" end="38">&lt;-</LEFT_ASSIGN>
    <expr line1="1" col1="9" line2="3" col2="1" start="40" end="94">
      <FUNCTION line1="1" col1="9" line2="1" col2="16" start="40" end="47">function</FUNCTION>
      <OP-LEFT-PAREN line1="1" col1="17" line2="1" col2="17" start="48" end="48">(</OP-LEFT-PAREN>
      <SYMBOL_FORMALS line1="1" col1="18" line2="1" col2="21" start="49" end="52">var1</SYMBOL_FORMALS>
      <OP-COMMA line1="1" col1="22" line2="1" col2="22" start="53" end="53">,</OP-COMMA>
      <SYMBOL_FORMALS line1="1" col1="24" line2="1" col2="27" start="55" end="58">var2</SYMBOL_FORMALS>
      <OP-RIGHT-PAREN line1="1" col1="28" line2="1" col2="28" start="59" end="59">)</OP-RIGHT-PAREN>
      <expr line1="1" col1="30" line2="3" col2="1" start="61" end="94">
        <OP-LEFT-BRACE line1="1" col1="30" line2="1" col2="30" start="61" end="61">{</OP-LEFT-BRACE>
        <expr line1="2" col1="3" line2="2" col2="13" start="65" end="75">
          <expr line1="2" col1="3" line2="2" col2="6" start="65" end="68">
            <SYMBOL line1="2" col1="3" line2="2" col2="6" start="65" end="68">var1</SYMBOL>
          </expr>
          <OP-PLUS line1="2" col1="8" line2="2" col2="8" start="70" end="70">+</OP-PLUS>
          <expr line1="2" col1="10" line2="2" col2="13" start="72" end="75">
            <SYMBOL line1="2" col1="10" line2="2" col2="13" start="72" end="75">var2</SYMBOL>
          </expr>
        </expr>
        <OP-RIGHT-BRACE line1="3" col1="1" line2="3" col2="1" start="94" end="94">}</OP-RIGHT-BRACE>
      </expr>
    </expr>
  </expr>
  <expr line1="5" col1="1" line2="7" col2="1" start="156" end="218">
    <expr line1="5" col1="1" line2="5" col2="4" start="156" end="159">
      <SYMBOL line1="5" col1="1" line2="5" col2="4" start="156" end="159">fun2</SYMBOL>
    </expr>
    <LEFT_ASSIGN line1="5" col1="6" line2="5" col2="7" start="161" end="162">&lt;-</LEFT_ASSIGN>
    <expr line1="5" col1="9" line2="7" col2="1" start="164" end="218">
      <OP-LAMBDA line1="5" col1="9" line2="5" col2="9" start="164" end="164">\</OP-LAMBDA>
      <OP-LEFT-PAREN line1="5" col1="10" line2="5" col2="10" start="165" end="165">(</OP-LEFT-PAREN>
      <SYMBOL_FORMALS line1="5" col1="11" line2="5" col2="14" start="166" end="169">var1</SYMBOL_FORMALS>
      <OP-COMMA line1="5" col1="15" line2="5" col2="15" start="170" end="170">,</OP-COMMA>
      <SYMBOL_FORMALS line1="5" col1="17" line2="5" col2="20" start="172" end="175">var2</SYMBOL_FORMALS>
      <OP-RIGHT-PAREN line1="5" col1="21" line2="5" col2="21" start="176" end="176">)</OP-RIGHT-PAREN>
      <expr line1="5" col1="23" line2="7" col2="1" start="178" end="218">
        <OP-LEFT-BRACE line1="5" col1="23" line2="5" col2="23" start="178" end="178">{</OP-LEFT-BRACE>
        <expr line1="6" col1="3" line2="6" col2="13" start="189" end="199">
          <expr line1="6" col1="3" line2="6" col2="6" start="189" end="192">
            <SYMBOL line1="6" col1="3" line2="6" col2="6" start="189" end="192">var1</SYMBOL>
          </expr>
          <OP-PLUS line1="6" col1="8" line2="6" col2="8" start="194" end="194">+</OP-PLUS>
          <expr line1="6" col1="10" line2="6" col2="13" start="196" end="199">
            <SYMBOL line1="6" col1="10" line2="6" col2="13" start="196" end="199">var2</SYMBOL>
          </expr>
        </expr>
        <OP-RIGHT-BRACE line1="7" col1="1" line2="7" col2="1" start="218" end="218">}</OP-RIGHT-BRACE>
      </expr>
    </expr>
  </expr>
</exprlist>

Looks like we could extend all uses of FUNCTION to also support OP-LAMBDA in all XPaths used in the language providers.