C++ backend: use .noInit pragma for non-public default constructors; refs #4687

compiler/ast.nim

@@ -437,7 +437,7 @@ type
     nfExplicitCall # x.y() was used instead of x.y
     nfExprCall  # this is an attempt to call a regular expression
     nfIsRef     # this node is a 'ref' node; used for the VM
-    nfIsCursor  # this node is attached a cursor; used for idetools
+    nfPreventCg # this node should be ignored by the codegen
 
   TNodeFlags* = set[TNodeFlag]
   TTypeFlag* = enum   # keep below 32 for efficiency reasons (now: 28)
@@ -925,7 +925,7 @@ const
     skMacro, skTemplate, skConverter, skEnumField, skLet, skStub, skAlias}
   PersistentNodeFlags*: TNodeFlags = {nfBase2, nfBase8, nfBase16,
                                       nfDotSetter, nfDotField,
-                                      nfIsRef, nfIsCursor, nfLL}
+                                      nfIsRef, nfPreventCg, nfLL}
   namePos* = 0
   patternPos* = 1    # empty except for term rewriting macros
   genericParamsPos* = 2

compiler/ccgexprs.nim

@@ -2084,8 +2084,11 @@ proc expr(p: BProc, n: PNode, d: var TLoc) =
   of nkCaseStmt: genCase(p, n, d)
   of nkReturnStmt: genReturnStmt(p, n)
   of nkBreakStmt: genBreakStmt(p, n)
-  of nkAsgn: genAsgn(p, n, fastAsgn=false)
+  of nkAsgn:
+    if nfPreventCg notin n.flags:
+      genAsgn(p, n, fastAsgn=false)
   of nkFastAsgn:
+    if nfPreventCg notin n.flags:
       # transf is overly aggressive with 'nkFastAsgn', so we work around here.
       # See tests/run/tcnstseq3 for an example that would fail otherwise.
       genAsgn(p, n, fastAsgn=p.prc != nil)

compiler/ccgstmts.nim

@@ -359,6 +359,7 @@ proc blockLeaveActions(p: BProc, howManyTrys, howManyExcepts: int) =
       linefmt(p, cpsStmts, "#popCurrentException();$n")
 
 proc genReturnStmt(p: BProc, t: PNode) =
+  if nfPreventCg in t.flags: return
   p.beforeRetNeeded = true
   genLineDir(p, t)
   if (t.sons[0].kind != nkEmpty): genStmts(p, t.sons[0])

compiler/cgen.nim

@@ -616,6 +616,24 @@ proc closureSetup(p: BProc, prc: PSym) =
   linefmt(p, cpsStmts, "$1 = ($2) ClEnv;$n",
           rdLoc(env.loc), getTypeDesc(p.module, env.typ))
 
+proc easyResultAsgn(n: PNode): PNode =
+  const harmless = {nkConstSection, nkTypeSection, nkEmpty, nkCommentStmt} +
+                    declarativeDefs
+  case n.kind
+  of nkStmtList, nkStmtListExpr:
+    var i = 0
+    while i < n.len and n[i].kind in harmless: inc i
+    if i < n.len: result = easyResultAsgn(n[i])
+  of nkAsgn, nkFastAsgn:
+    if n[0].kind == nkSym and skResult == n[0].sym.kind:
+      incl n.flags, nfPreventCg
+      return n[1]
+  of nkReturnStmt:
+    if n.len > 0:
+      result = easyResultAsgn(n[0])
+      if result != nil: incl n.flags, nfPreventCg
+  else: discard
+
 proc genProcAux(m: BModule, prc: PSym) =
   var p = newProc(prc, m)
   var header = genProcHeader(m, prc)
@@ -627,11 +645,17 @@ proc genProcAux(m: BModule, prc: PSym) =
     var res = prc.ast.sons[resultPos].sym # get result symbol
     if not isInvalidReturnType(prc.typ.sons[0]):
       if sfNoInit in prc.flags: incl(res.flags, sfNoInit)
+      if sfNoInit in prc.flags and p.module.compileToCpp and (let val = easyResultAsgn(prc.getBody); val != nil):
+        var decl = localVarDecl(p, res)
+        var a: TLoc
+        initLocExprSingleUse(p, val, a)
+        linefmt(p, cpsStmts, "$1 = $2;$n", decl, rdLoc(a))
+      else:
         # declare the result symbol:
         assignLocalVar(p, res)
         assert(res.loc.r != nil)
-      returnStmt = rfmt(nil, "\treturn $1;$n", rdLoc(res.loc))
         initLocalVar(p, res, immediateAsgn=false)
+      returnStmt = rfmt(nil, "\treturn $1;$n", rdLoc(res.loc))
     else:
       fillResult(res)
       assignParam(p, res)
@@ -791,12 +815,12 @@ proc addIntTypes(result: var Rope) {.inline.} =
 proc getCopyright(cfile: string): Rope =
   if optCompileOnly in gGlobalOptions:
     result = ("/* Generated by Nim Compiler v$1 */$N" &
-        "/*   (c) 2015 Andreas Rumpf */$N" &
+        "/*   (c) 2016 Andreas Rumpf */$N" &
         "/* The generated code is subject to the original license. */$N") %
         [rope(VersionAsString)]
   else:
     result = ("/* Generated by Nim Compiler v$1 */$N" &
-        "/*   (c) 2015 Andreas Rumpf */$N" &
+        "/*   (c) 2016 Andreas Rumpf */$N" &
         "/* The generated code is subject to the original license. */$N" &
         "/* Compiled for: $2, $3, $4 */$N" &
         "/* Command for C compiler:$n   $5 */$N") %

compiler/suggest.nim

@@ -413,7 +413,6 @@ proc safeSemExpr*(c: PContext, n: PNode): PNode =
     result = ast.emptyNode
 
 proc suggestExpr*(c: PContext, node: PNode) =
-  if nfIsCursor notin node.flags:
   if gTrackPos.line < 0: return
   var cp = inCheckpoint(node.info)
   if cp == cpNone: return
@@ -423,7 +422,7 @@ proc suggestExpr*(c: PContext, node: PNode) =
   inc(c.compilesContextId)
 
   if gIdeCmd == ideSug:
-    var n = if nfIsCursor in node.flags: node else: findClosestDot(node)
+    var n = findClosestDot(node)
     if n == nil: n = node
     if n.kind == nkDotExpr:
       var obj = safeSemExpr(c, n.sons[0])
@@ -436,7 +435,7 @@ proc suggestExpr*(c: PContext, node: PNode) =
       suggestEverything(c, n, outputs)
 
   elif gIdeCmd == ideCon:
-    var n = if nfIsCursor in node.flags: node else: findClosestCall(node)
+    var n = findClosestCall(node)
     if n == nil: n = node
     if n.kind in nkCallKinds:
       var a = copyNode(n)