prepare for #3898

compiler/parser.nim

@@ -686,11 +686,19 @@ proc primarySuffix(p: var TParser, r: PNode, baseIndent: int): PNode =
   #|       | '{' optInd indexExprList optPar '}'
   #|       | &( '`'|IDENT|literal|'cast'|'addr'|'type') expr # command syntax
   result = r
+
+  template somePar() =
+    if p.tok.strongSpaceA > 0:
+      if p.strongSpaces:
+        break
+      else:
+        parMessage(p, warnDeprecated,
+          "a [b] will be parsed as command syntax; spacing")
   while p.tok.indent < 0 or
        (p.tok.tokType == tkDot and p.tok.indent >= baseIndent):
     case p.tok.tokType
     of tkParLe:
-      if p.strongSpaces and p.tok.strongSpaceA > 0: break
+      somePar()
       result = namedParams(p, result, nkCall, tkParRi)
       if result.len > 1 and result.sons[1].kind == nkExprColonExpr:
         result.kind = nkObjConstr
@@ -705,10 +713,10 @@ proc primarySuffix(p: var TParser, r: PNode, baseIndent: int): PNode =
       result = dotExpr(p, result)
       result = parseGStrLit(p, result)
     of tkBracketLe:
-      if p.strongSpaces and p.tok.strongSpaceA > 0: break
+      somePar()
       result = namedParams(p, result, nkBracketExpr, tkBracketRi)
     of tkCurlyLe:
-      if p.strongSpaces and p.tok.strongSpaceA > 0: break
+      somePar()
       result = namedParams(p, result, nkCurlyExpr, tkCurlyRi)
     of tkSymbol, tkAccent, tkIntLit..tkCharLit, tkNil, tkCast, tkAddr, tkType:
       if p.inPragma == 0:

web/news/version_0_15_released.rst

@@ -17,7 +17,18 @@ Changes affecting backwards compatibility
   no longer strips and splits characters out of the target string
   by the entire set of characters. Instead, it now behaves in a
   similar fashion to ``split`` with ``string`` and ``char``
-  delimiters.
+  delimiters. Use ``splitWhitespace`` to get the old behaviour.
+- The command invocation syntax will soon apply to open brackets
+  and curlies too. This means that code like ``a [i]`` will be
+  interpreted as ``a([i])`` and not as ``a[i]`` anymore. Likewise
+  ``f (a, b)`` means that the tuple ``(a, b)`` is passed to ``f``.
+  The compiler produces a warning for ``a [i]``::
+
+    Warning: a [b] will be parsed as command syntax; spacing is deprecated
+
+  See `https://github.com/nim-lang/Nim/issues/3898`_ for the relevant
+  discussion.
+
 
 Library Additions
 -----------------