language change: change how the experimental dot operators work

changelog.md

@@ -111,3 +111,9 @@ This now needs to be written as:
 - ``strutils.split`` and ``strutils.rsplit`` with an empty string and a
   separator now returns that empty string.
   See issue [#4377](https://github.com/nim-lang/Nim/issues/4377).
+- The experimental overloading of the dot ``.`` operators now take
+  an ``untyped``` parameter as the field name, it used to be
+  a ``static[string]``. You can use ``when defined(nimNewDot)`` to make
+  your code work with both old and new Nim versions.
+  See [special-operators](https://nim-lang.org/docs/manual.html#special-operators)
+  for more information.

compiler/condsyms.nim

@@ -111,3 +111,4 @@ proc initDefines*() =
   defineSymbol("nimNoArrayToCstringConversion")
   defineSymbol("nimNewRoof")
   defineSymbol("nimHasRunnableExamples")
+  defineSymbol("nimNewDot")

compiler/semcall.nim

@@ -235,12 +235,11 @@ proc resolveOverloads(c: PContext, n, orig: PNode,
 
     if nfDotField in n.flags:
       internalAssert f.kind == nkIdent and n.sonsLen >= 2
-      let calleeName = newStrNode(nkStrLit, f.ident.s).withInfo(n.info)
 
       # leave the op head symbol empty,
       # we are going to try multiple variants
-      n.sons[0..1] = [nil, n[1], calleeName]
-      orig.sons[0..1] = [nil, orig[1], calleeName]
+      n.sons[0..1] = [nil, n[1], f]
+      orig.sons[0..1] = [nil, orig[1], f]
 
       template tryOp(x) =
         let op = newIdentNode(getIdent(x), n.info)
@@ -255,8 +254,8 @@ proc resolveOverloads(c: PContext, n, orig: PNode,
         tryOp "."
 
     elif nfDotSetter in n.flags and f.kind == nkIdent and n.len == 3:
-      let calleeName = newStrNode(nkStrLit,
-        f.ident.s[0..f.ident.s.len-2]).withInfo(n.info)
+      # we need to strip away the trailing '=' here:
+      let calleeName = newIdentNode(getIdent(f.ident.s[0..f.ident.s.len-2]), n.info)
       let callOp = newIdentNode(getIdent".=", n.info)
       n.sons[0..1] = [callOp, n[1], calleeName]
       orig.sons[0..1] = [callOp, orig[1], calleeName]

doc/manual/special_ops.txt

@@ -17,8 +17,8 @@ or dynamic file formats such as JSON or XML.
 When Nim encounters an expression that cannot be resolved by the
 standard overload resolution rules, the current scope will be searched
 for a dot operator that can be matched against a re-written form of
-the expression, where the unknown field or proc name is converted to
-an additional static string parameter:
+the expression, where the unknown field or proc name is passed to
+an ``untyped`` parameter:
 
 .. code-block:: nim
   a.b # becomes `.`(a, "b")
@@ -28,7 +28,7 @@ The matched dot operators can be symbols of any callable kind (procs,
 templates and macros), depending on the desired effect:
 
 .. code-block:: nim
-  proc `.` (js: PJsonNode, field: string): JSON = js[field]
+  template `.` (js: PJsonNode, field: untyped): JSON = js[astToStr(field)]
 
   var js = parseJson("{ x: 1, y: 2}")
   echo js.x # outputs 1

lib/js/jsffi.nim

@@ -177,7 +177,7 @@ proc `==`*(x, y: JsRoot): bool {. importcpp: "(# === #)" .}
   ## and not strings or numbers, this is a *comparison of references*.
 
 {. experimental .}
-macro `.`*(obj: JsObject, field: static[cstring]): JsObject =
+macro `.`*(obj: JsObject, field: untyped): JsObject =
   ## Experimental dot accessor (get) for type JsObject.
   ## Returns the value of a property of name `field` from a JsObject `x`.
   ##
@@ -196,14 +196,14 @@ macro `.`*(obj: JsObject, field: static[cstring]): JsObject =
       helper(`obj`)
   else:
     if not mangledNames.hasKey($field):
-      mangledNames[$field] = $mangleJsName(field)
+      mangledNames[$field] = $mangleJsName($field)
     let importString = "#." & mangledNames[$field]
     result = quote do:
       proc helper(o: JsObject): JsObject
         {. importcpp: `importString`, gensym .}
       helper(`obj`)
 
-macro `.=`*(obj: JsObject, field: static[cstring], value: untyped): untyped =
+macro `.=`*(obj: JsObject, field, value: untyped): untyped =
   ## Experimental dot accessor (set) for type JsObject.
   ## Sets the value of a property of name `field` in a JsObject `x` to `value`.
   if validJsName($field):
@@ -214,7 +214,7 @@ macro `.=`*(obj: JsObject, field: static[cstring], value: untyped): untyped =
       helper(`obj`, `value`)
   else:
     if not mangledNames.hasKey($field):
-      mangledNames[$field] = $mangleJsName(field)
+      mangledNames[$field] = $mangleJsName($field)
     let importString = "#." & mangledNames[$field] & " = #"
     result = quote do:
       proc helper(o: JsObject, v: auto)
@@ -222,7 +222,7 @@ macro `.=`*(obj: JsObject, field: static[cstring], value: untyped): untyped =
       helper(`obj`, `value`)
 
 macro `.()`*(obj: JsObject,
-             field: static[cstring],
+             field: untyped,
              args: varargs[JsObject, jsFromAst]): JsObject =
   ## Experimental "method call" operator for type JsObject.
   ## Takes the name of a method of the JavaScript object (`field`) and calls
@@ -245,7 +245,7 @@ macro `.()`*(obj: JsObject,
     importString = "#." & $field & "(@)"
   else:
     if not mangledNames.hasKey($field):
-      mangledNames[$field] = $mangleJsName(field)
+      mangledNames[$field] = $mangleJsName($field)
     importString = "#." & mangledNames[$field] & "(@)"
   result = quote:
     proc helper(o: JsObject): JsObject
@@ -257,7 +257,7 @@ macro `.()`*(obj: JsObject,
     result[1].add args[idx].copyNimTree
 
 macro `.`*[K: string | cstring, V](obj: JsAssoc[K, V],
-                                   field: static[cstring]): V =
+                                   field: untyped): V =
   ## Experimental dot accessor (get) for type JsAssoc.
   ## Returns the value of a property of name `field` from a JsObject `x`.
   var importString: string
@@ -265,7 +265,7 @@ macro `.`*[K: string | cstring, V](obj: JsAssoc[K, V],
     importString = "#." & $field
   else:
     if not mangledNames.hasKey($field):
-      mangledNames[$field] = $mangleJsName(field)
+      mangledNames[$field] = $mangleJsName($field)
     importString = "#." & mangledNames[$field]
   result = quote do:
     proc helper(o: type(`obj`)): `obj`.V
@@ -273,7 +273,7 @@ macro `.`*[K: string | cstring, V](obj: JsAssoc[K, V],
     helper(`obj`)
 
 macro `.=`*[K: string | cstring, V](obj: JsAssoc[K, V],
-                                    field: static[cstring],
+                                    field: untyped,
                                     value: V): untyped =
   ## Experimental dot accessor (set) for type JsAssoc.
   ## Sets the value of a property of name `field` in a JsObject `x` to `value`.
@@ -282,7 +282,7 @@ macro `.=`*[K: string | cstring, V](obj: JsAssoc[K, V],
     importString = "#." & $field & " = #"
   else:
     if not mangledNames.hasKey($field):
-      mangledNames[$field] = $mangleJsName(field)
+      mangledNames[$field] = $mangleJsName($field)
     importString = "#." & mangledNames[$field] & " = #"
   result = quote do:
     proc helper(o: type(`obj`), v: `obj`.V)
@@ -290,7 +290,7 @@ macro `.=`*[K: string | cstring, V](obj: JsAssoc[K, V],
     helper(`obj`, `value`)
 
 macro `.()`*[K: string | cstring, V: proc](obj: JsAssoc[K, V],
-                                           field: static[cstring],
+                                           field: untyped,
                                            args: varargs[untyped]): auto =
   ## Experimental "method call" operator for type JsAssoc.
   ## Takes the name of a method of the JavaScript object (`field`) and calls