syntax compatibility between do blocks and stmt blocks

See the section `do notation` in the manual for more info.

* nkMacroStmt has been removed
   Macro statements are now mapped to regular nkCall nodes.
   The support for additional clauses (such as else, except, of, etc)
   have been restored - they will now appear as additional arguments
   for the nkCall node (as nkElse, nkExcept, etc nodes)

* fixed some regressions in the `is` operator and semCompiles

lib/core/macros.nim

@@ -38,7 +38,7 @@ type
     nnkFastAsgn, nnkGenericParams, nnkFormalParams, nnkOfInherit,
     nnkModule, nnkProcDef, nnkMethodDef, nnkConverterDef,
     nnkMacroDef, nnkTemplateDef, nnkIteratorDef, nnkOfBranch,
-    nnkElifBranch, nnkExceptBranch, nnkElse, nnkMacroStmt,
+    nnkElifBranch, nnkExceptBranch, nnkElse,
     nnkAsmStmt, nnkPragma, nnkPragmaBlock, nnkIfStmt, nnkWhenStmt,
     nnkForStmt, nnkParForStmt, nnkWhileStmt, nnkCaseStmt,
     nnkTypeSection, nnkVarSection, nnkLetSection, nnkConstSection,

lib/impure/graphics.nim

@@ -22,7 +22,7 @@ type
 
   PSurface* = ref TSurface ## a surface to draw onto
   TSurface* {.pure, final.} = object
-    w*, h*: int
+    w*, h*: Natural
     s*: sdl.PSurface
   
   EGraphics* = object of EIO

lib/pure/sockets.nim

@@ -940,7 +940,7 @@ proc readIntoBuf(socket: TSocket, flags: int32): int =
   socket.currPos = 0
 
 template retRead(flags, readBytes: int) =
-  let res = socket.readIntoBuf(flags)
+  let res = socket.readIntoBuf(flags.int32)
   if res <= 0:
     if readBytes > 0:
       return readBytes

lib/pure/unittest.nim

@@ -151,7 +151,7 @@ template require*(conditions: stmt): stmt {.immediate, dirty.} =
     const AbortOnError {.inject.} = true
     check conditions
 
-macro expect*(exp: stmt): stmt {.immediate.} =
+macro expect*(exceptions: varargs[expr], body: stmt): stmt {.immediate.} =
   let exp = callsite()
   template expectBody(errorTypes, lineInfoLit: expr,
                       body: stmt): PNimrodNode {.dirty.} =
@@ -162,12 +162,11 @@ macro expect*(exp: stmt): stmt {.immediate.} =
     except errorTypes:
       nil
 
-  var expectCall = exp[0]
-  var body = exp[1]
-  
+  var body = exp[exp.len - 1]
+
   var errorTypes = newNimNode(nnkBracket)
-  for i in countup(1, expectCall.len - 1):
-    errorTypes.add(expectCall[i])
+  for i in countup(1, exp.len - 2):
+    errorTypes.add(exp[i])
 
   result = getAst(expectBody(errorTypes, exp.lineinfo, body))