Default fields for objects

compiler/parser.nim

@@ -1898,11 +1898,7 @@ proc parseObjectCase(p: var TParser): PNode =
   #|             | IND{=} objectBranches)
   result = newNodeP(nkRecCase, p)
   getTokNoInd(p)
-  var a = newNodeP(nkIdentDefs, p)
-  a.add(identWithPragma(p))
-  eat(p, tkColon)
-  a.add(parseTypeDesc(p))
-  a.add(p.emptyNode)
+  var a = parseIdentColonEquals(p, {withPragma})
   result.add(a)
   if p.tok.tokType == tkColon: getTok(p)
   flexComment(p, result)

compiler/semtypes.nim

@@ -596,7 +596,7 @@ proc getIntSetOfType(c: PContext, t: PType): IntSet =
   result = initIntSet()
   if t.enumHasHoles:
     let t = t.skipTypes(abstractRange)
-    for field in t.n.sons:
+    for field in t.n:
       result.incl(field.sym.position)
   else:
     assert(lengthOrd(c.config, t) <= BiggestInt(MaxSetElements))
@@ -607,7 +607,7 @@ iterator processBranchVals(b: PNode): int =
   assert b.kind in {nkOfBranch, nkElifBranch, nkElse}
   if b.kind == nkOfBranch:
     for i in 0..<b.len-1:
-      if b[i].kind == nkIntLit:
+      if b[i].kind in {nkIntLit..nkUInt64Lit}:
         yield b[i].intVal.int
       elif b[i].kind == nkRange:
         for i in b[i][0].intVal..b[i][1].intVal:
@@ -742,18 +742,15 @@ proc semRecordNodeAux(c: PContext, n: PNode, check: var IntSet, pos: var int,
     if a != father: father.add a
   of nkIdentDefs:
     checkMinSonsLen(n, 3, c.config)
-    var a: PNode
-    if father.kind != nkRecList and n.len >= 4: a = newNodeI(nkRecList, n.info)
-    else: a = newNodeI(nkEmpty, n.info)
-    if n[^1].kind != nkEmpty:
-      localError(c.config, n[^1].info, errInitHereNotAllowed)
     var typ: PType
     if n[^2].kind == nkEmpty:
       localError(c.config, n.info, errTypeExpected)
       typ = errorType(c)
     else:
       typ = semTypeNode(c, n[^2], nil)
       propagateToOwner(rectype, typ)
+    var a: PNode = if father.kind != nkRecList and n.len > 3: newNodeI(nkRecList, n.info)
+                   else: newNodeI(nkEmpty, n.info)
     var fieldOwner = if c.inGenericContext > 0: c.getCurrOwner
                      else: rectype.sym
     for i in 0..<n.len-2:
@@ -774,6 +771,12 @@ proc semRecordNodeAux(c: PContext, n: PNode, check: var IntSet, pos: var int,
       inc(pos)
       if containsOrIncl(check, f.name.id):
         localError(c.config, info, "attempt to redefine: '" & f.name.s & "'")
+      var fSym = newSymNode(f)
+      if n[^1].kind != nkEmpty:
+        n[^1] = semConstExpr(c, n[^1])
+        fSym.sym.ast = n[^1]
+      elif typ.kind in {tyRange, tyOrdinal}: #Node flag? Handle embedded objects?
+        fSym.sym.ast = semConstExpr(c, newIntNode(nkIntLit, firstOrd(c.config, typ)))
       if a.kind == nkEmpty: father.add newSymNode(f)
       else: a.add newSymNode(f)
       styleCheckDef(c.config, f)

compiler/transf.nim

@@ -17,6 +17,7 @@
 # * introduces method dispatchers
 # * performs lambda lifting for closure support
 # * transforms 'defer' into a 'try finally' statement
+# * generates default field values for objects and transforms object contructors
 
 import
   options, ast, astalgo, trees, msgs,
@@ -44,7 +45,7 @@ type
     module: PSym
     transCon: PTransCon      # top of a TransCon stack
     inlining: int            # > 0 if we are in inlining context (copy vars)
-    nestedProcs: int         # > 0 if we are in a nested proc
+    genResult: bool          # XXX
     contSyms, breakSyms: seq[PSym]  # to transform 'continue' and 'break'
     deferDetected, tooEarly: bool
     graph: ModuleGraph
@@ -383,7 +384,7 @@ proc transformYield(c: PTransf, n: PNode): PNode =
       let rhs = transform(c, e)
       result.add(asgnTo(lhs, rhs))
 
-  inc(c.transCon.yieldStmts)
+  inc c.transCon.yieldStmts
   if c.transCon.yieldStmts <= 1:
     # common case
     result.add(c.transCon.forLoopBody)
@@ -658,7 +659,7 @@ proc transformFor(c: PTransf, n: PNode): PNode =
 
   let body = transformBody(c.graph, iter, true)
   pushInfoContext(c.graph.config, n.info)
-  inc(c.inlining)
+  inc c.inlining
   stmtList.add(transform(c, body))
   #findWrongOwners(c, stmtList.pnode)
   dec(c.inlining)
@@ -743,13 +744,13 @@ proc transformCall(c: PTransf, n: PNode): PNode =
     var j = 1
     while j < n.len:
       var a = transform(c, n[j])
-      inc(j)
+      inc j
       if isConstExpr(a):
         while (j < n.len):
           let b = transform(c, n[j])
           if not isConstExpr(b): break
           a = evalOp(op.magic, n, a, b, nil, c.graph)
-          inc(j)
+          inc j
       result.add(a)
     if result.len == 2: result = result[1]
   elif magic == mAddr:
@@ -828,13 +829,13 @@ proc commonOptimizations*(g: ModuleGraph; c: PSym, n: PNode): PNode =
     var j = 0
     while j < args.len:
       var a = args[j]
-      inc(j)
+      inc j
       if isConstExpr(a):
         while j < args.len:
           let b = args[j]
           if not isConstExpr(b): break
           a = evalOp(op.magic, result, a, b, nil, g)
-          inc(j)
+          inc j
       result.add(a)
     if result.len == 2: result = result[1]
   else:
@@ -882,6 +883,47 @@ proc hoistParamsUsedInDefault(c: PTransf, call, letSection, defExpr: PNode): PNo
       let hoisted = hoistParamsUsedInDefault(c, call, letSection, defExpr[i])
       if hoisted != nil: defExpr[i] = hoisted
 
+import nimsets
+proc caseBranchMatchesExpr(branch, matched: PNode): bool =
+  for i in 0 ..< branch.len-1:
+    if branch[i].kind == nkRange:
+      if overlap(branch[i], matched): return true
+    elif exprStructuralEquivalent(branch[i], matched):
+      return true
+
+proc pickCaseBranch(caseExpr, matched: PNode): int =
+  let endsWithElse = caseExpr[^1].kind == nkElse
+  for i in 1..<caseExpr.len - endsWithElse.int:
+    if caseExpr[i].caseBranchMatchesExpr(matched):
+      return i
+  if endsWithElse:
+    return caseExpr.len - 1
+
+proc defaultFieldsForTheUninitialized(c: PTransf, recNode: PNode): seq[PNode] =
+  case recNode.kind
+  of nkRecList:
+    for field in recNode:
+      result.add defaultFieldsForTheUninitialized(c, field)
+  of nkRecCase:
+    let discriminator = recNode[0]
+    var selectedBranch: int
+    let defaultValue = discriminator.sym.ast
+    if defaultValue == nil:
+      # None of the branches were explicitly selected by the user and no value
+      # was given to the discrimator. We can assume that it will be initialized
+      # to zero and this will select a particular branch as a result:
+      selectedBranch = recNode.pickCaseBranch newIntNode(nkIntLit#[c.graph]#, 0)
+    else: # Try to use default value
+      selectedBranch = recNode.pickCaseBranch defaultValue
+      result.add newTree(nkExprColonExpr, discriminator, defaultValue)
+    result.add defaultFieldsForTheUninitialized(c, recNode[selectedBranch][^1])
+  of nkSym:
+    let field = recNode.sym
+    if field.ast != nil: #Try to use default value
+      result.add newTree(nkExprColonExpr, recNode, field.ast)
+  else:
+    assert false
+
 proc transform(c: PTransf, n: PNode): PNode =
   when false:
     var oldDeferAnchor: PNode
@@ -890,6 +932,18 @@ proc transform(c: PTransf, n: PNode): PNode =
                   nkBlockStmt, nkBlockExpr}:
       oldDeferAnchor = c.deferAnchor
       c.deferAnchor = n
+  if c.genResult:
+    c.genResult = false
+    result = newNodeIT(nkStmtList, n.info, nil)
+    let toInit = c.getCurrOwner().ast[resultPos]
+    if toInit.typ != nil and toInit.typ.kind == tyObject:
+      var asgnExpr = newTree(nkObjConstr, newNodeIT(nkType, toInit.info, toInit.typ))
+      asgnExpr.typ = toInit.typ
+      #TODO: Once the VM is ready this should be done in injectdestructors so that it can be elided properly
+      asgnExpr.sons.add defaultFieldsForTheUninitialized(c, toInit.typ.n)
+      result.add transform(c, newTree(nkAsgn, toInit, asgnExpr))
+    result.add transform(c, n)
+    return result
   case n.kind
   of nkSym:
     result = transformSym(c, n)
@@ -947,17 +1001,26 @@ proc transform(c: PTransf, n: PNode): PNode =
     result.add(newSymNode(labl))
   of nkBreakStmt: result = transformBreak(c, n)
   of nkCallKinds:
-    result = transformCall(c, n)
-    var call = result
-    if nfDefaultRefsParam in call.flags:
-      # We've found a default value that references another param.
-      # See the notes in `hoistParamsUsedInDefault` for more details.
-      var hoistedParams = newNodeI(nkLetSection, call.info, 0)
-      for i in 1..<call.len:
-        let hoisted = hoistParamsUsedInDefault(c, call, hoistedParams, call[i])
-        if hoisted != nil: call[i] = hoisted
-      result = newTree(nkStmtListExpr, hoistedParams, call)
-      result.typ = call.typ
+    # if (n[0].kind == nkSym) and (n[0].sym.magic == mReset) and (n[1].typ.kind == tyObject):
+    #   result = newNodeIT(nkStmtList, n.info, n.typ)
+    #   result.add transformCall(c, n)
+    #   result.add initDefaultFields(n[1], n[1].typ.n)
+    # elif (n[0].kind == nkSym) and (n[0].sym.magic in {mNew, mNewFinalize}) and (n[1].typ.kind == tyRef):
+    #   result = newNodeIT(nkStmtListExpr, n.info, n.typ)
+    #   result.add transformCall(c, n)
+    #   result.add initDefaultFields(n[1], n[1].typ[0].n)
+    # else:
+      result = transformCall(c, n)
+      var call = result
+      if nfDefaultRefsParam in call.flags:
+        # We've found a default value that references another param.
+        # See the notes in `hoistParamsUsedInDefault` for more details.
+        var hoistedParams = newNodeI(nkLetSection, call.info, 0)
+        for i in 1 ..< call.len:
+          let hoisted = hoistParamsUsedInDefault(c, call, hoistedParams, call[i])
+          if hoisted != nil: call[i] = hoisted
+        result = newTree(nkStmtListExpr, hoistedParams, call)
+        result.typ = call.typ
   of nkAddr, nkHiddenAddr:
     result = transformAddrDeref(c, n, nkDerefExpr, nkHiddenDeref)
   of nkDerefExpr, nkHiddenDeref:
@@ -1013,6 +1076,13 @@ proc transform(c: PTransf, n: PNode): PNode =
     return n
   of nkExceptBranch:
     result = transformExceptBranch(c, n)
+  of nkObjConstr:
+    result = n
+    if result.typ.skipTypes(abstractInst).kind == tyObject or
+       result.typ.skipTypes(abstractInst).kind == tyRef and result.typ.skipTypes(abstractInst)[0].kind == tyObject:
+      result.sons.add result[0].sons
+      result[0] = newNodeIT(nkType, result.info, result.typ)
+    result = transformSons(c, result)
   else:
     result = transformSons(c, n)
   when false:
@@ -1034,6 +1104,7 @@ proc processTransf(c: PTransf, n: PNode, owner: PSym): PNode =
   # nodes into an empty node.
   if nfTransf in n.flags: return n
   pushTransCon(c, newTransCon(owner))
+  c.genResult = c.getCurrOwner().kind in routineKinds and c.transCon.owner.ast.len > resultPos and c.transCon.owner.ast[resultPos] != nil
   result = transform(c, n)
   popTransCon(c)
   incl(result.flags, nfTransf)

compiler/vmgen.nim

@@ -1639,7 +1639,7 @@ proc genRdVar(c: PCtx; n: PNode; dest: var TDest; flags: TGenFlags) =
   else:
     if s.kind == skForVar and c.mode == emRepl: c.setSlot(s)
     if s.position > 0 or (s.position == 0 and
-                          s.kind in {skParam, skResult}):
+                          s.kind in {skParam, skResult, skTemp}):
       if dest < 0:
         dest = s.position + ord(s.kind == skParam)
         internalAssert(c.config, c.prc.slots[dest].kind < slotSomeTemp)

tests/constructors/tinvalid_construction.nim

@@ -65,7 +65,7 @@ accept TObj()
 accept TObj(choice: A)
 reject TObj(choice: A, bc: 10)  # bc is in the wrong branch
 accept TObj(choice: B, bc: 20)
-reject TObj(a: 10)              # branch selected without providing discriminator
+accept TObj(a: 10)              # branch selected with the default value "low(T)" of the discriminator
 reject TObj(choice: x, a: 10)   # the discrimantor must be a compile-time value when a branch is selected
 accept TObj(choice: x)          # it's OK to use run-time value when a branch is not selected
 accept TObj(choice: F, f: "")   # match an else clause

tests/objvariant/trt_discrim.nim

@@ -133,6 +133,12 @@ reject:
 var varkind = k4
 
 reject: # not immutable.
+  case varkind
+  of k1, k2, k3: discard KindObj(kind: varkind, i32: 1)
+  of k4: discard KindObj(kind: varkind, f32: 2.0)
+  else: discard KindObj(kind: varkind, str: "3")
+
+reject: # complete bogus
   case varkind
   of k1, k2, k3: discard KindObj(varkind: kind, i32: 1)
   of k4: discard KindObj(varkind: kind, f32: 2.0)

tests/objvariant/trt_discrim_err0.nim

@@ -1,5 +1,5 @@
 discard """
-  errormsg: "possible values {k1, k3, k4} are in conflict with discriminator values for selected object branch 3"
+  errormsg: "runtime discriminator could select multiple branches, so you can't initialize these fields: str"
   line: 17
 """
 

tests/objvariant/trt_discrim_err1.nim

@@ -1,5 +1,5 @@
 discard """
-  errormsg: "branch initialization with a runtime discriminator is not supported inside of an `elif` branch."
+  errormsg: "runtime discriminator could select multiple branches, so you can't initialize these fields: green"
   line: 16
 """
 type

tests/objvariant/trt_discrim_err3.nim

@@ -1,5 +1,5 @@
 discard """
-  errormsg: "runtime discriminator must be immutable if branch fields are initialized, a 'let' binding is required."
+  errormsg: "runtime discriminator could select multiple branches, so you can't initialize these fields: i32"
   line: 16
 """