Merge pull request #2503 from ReneSac/arrowLike

Restrict arrow-like operators to those ending with `->`, `~>` or `=>`

compiler/parser.nim

@@ -212,7 +212,8 @@ proc getPrecedence(tok: TToken, strongSpaces: bool): int =
     let relevantChar = tok.ident.s[0]
 
     # arrow like?
-    if L > 1 and tok.ident.s[L-1] == '>': return considerStrongSpaces(1)
+    if L > 1 and tok.ident.s[L-1] == '>' and
+      tok.ident.s[L-2] in {'-', '~', '='}: return considerStrongSpaces(1)
 
     template considerAsgn(value: expr) =
       result = if tok.ident.s[L-1] == '=': 1 else: value

doc/manual/syntax.txt

@@ -15,8 +15,6 @@ Associativity
 Binary operators whose first character is ``^`` are right-associative, all
 other binary operators are left-associative.
 
-Operators ending in ``>`` but longer than a single character are 
-called `arrow like`:idx:.
 
 
 Precedence
@@ -33,9 +31,12 @@ as ``(@x).abc`` whereas ``$x.abc`` is parsed as ``$(x.abc)``.
 For binary operators that are not keywords the precedence is determined by the
 following rules:
 
+Operators ending in either ``->``, ``~>`` or ``=>`` are called
+`arrow like`:idx:, and have the lowest precedence of all operators.
+
 If the operator ends with ``=`` and its first character is none of 
 ``<``, ``>``, ``!``, ``=``, ``~``, ``?``, it is an *assignment operator* which
-has the lowest precedence.
+has the second lowest precedence.
 
 Otherwise precedence is determined by the first character.
 
@@ -43,14 +44,14 @@ Otherwise precedence is determined by the first character.
 Precedence level    Operators                                      First character     Terminal symbol
 ================  ===============================================  ==================  ===============
  10 (highest)                                                      ``$  ^``            OP10
-  9               ``*    /    div   mod   shl  shr  %``            ``* % \  /``        OP9
+  9               ``*    /    div   mod   shl  shr  %``            ``*  %  \  /``      OP9
-  8               ``+    -``                                       ``+  ~  |``         OP8
+  8               ``+    -``                                       ``+  -  ~  |``      OP8
   7               ``&``                                            ``&``               OP7
   6               ``..``                                           ``.``               OP6
-  5               ``==  <= < >= > !=  in notin is isnot not of``   ``= <  > !``        OP5
+  5               ``==  <= < >= > !=  in notin is isnot not of``   ``=  <  >  !``      OP5
   4               ``and``                                                              OP4
   3               ``or xor``                                                           OP3
-  2                                                                ``@  : ?``          OP2
+  2                                                                ``@  :  ?``         OP2
   1               *assignment operator* (like ``+=``, ``*=``)                          OP1
   0 (lowest)      *arrow like operator* (like ``->``, ``=>``)                          OP0
 ================  ===============================================  ==================  ===============
@@ -67,7 +68,7 @@ is still parsed as ``1 + (3 * 4)``, but ``1+3 * 4`` is parsed as ``(1+3) * 4``:
 
 .. code-block:: nim
   #! strongSpaces
-  if foo+4 * 4 == 8 and b&c | 9  ++
+  if foo+4 * 4 == 8  and  b&c | 9  ++
       bar:
     echo ""
   # is parsed as

tests/parser/tstrongspaces.nim

@@ -15,6 +15,10 @@ true
 tester args
 all
 all args
+19
+-3
+false
+-2
 '''
 """
 
@@ -67,3 +71,13 @@ const
 echo tester & " " & args|"all"
 echo "all"  |  tester & " " & args
 echo "all"|tester & " " & args
+
+# Test arrow like operators. See also tests/macros/tclosuremacro.nim
+proc `+->`(a, b: int): int = a + b*4
+template `===>`(a, b: int): expr = a - b shr 1
+
+echo 3 +-> 2 + 2 and 4
+var arrowed = 3+->2 + 2 and 4  # arrowed = 4
+echo arrowed ===> 15
+echo (2 * 3+->2) == (2*3 +-> 2)
+echo arrowed ===> 2 + 3+->2

web/news.txt

@@ -34,6 +34,10 @@ News
     should be used instead.
   - ``nim idetools`` has been replaced by a separate tool `nimsuggest`_.
   - *arrow like* operators are not right associative anymore.
+  - *arrow like* operators are now required to end with either ``->``, ``~>`` or
+    ``=>``, not just ``>``. Examples of operators still considered arrow like:
+    ``->``, ``==>``, ``+=>``. On the other hand, the following operators are now
+    considered regular operators again: ``|>``, ``-+>``, etc.
   - Typeless parameters are now only allowed in templates and macros. The old
     way turned out to be too error-prone.
   - The 'addr' and 'type' operators are now parsed as unary function