better error messages

compiler/semobjconstr.nim

@@ -414,6 +414,7 @@ proc defaultConstructionError(c: PContext, t: PType, info: TLineInfo) =
 
 proc replaceObjConstr(c: PContext; field: PNode, result: PNode, iterField: var int, flags: TExprFlags) =
   if iterField >= result.len:
+    inc iterField
     return
   case field.kind
   of nkRecCase:
@@ -438,7 +439,7 @@ proc replaceObjConstr(c: PContext; field: PNode, result: PNode, iterField: var i
     elif field.sym.name.id == considerQuotedIdent(c, result[iterField][0]).id:
       inc iterField
     else:
-      discard
+      localError(c.config, result.info, "When mixing named fields and unnamed fields, every field needs to be initialized in order")
   of nkRecList:
     for f in field:
       replaceObjConstr(c, f, result, iterField, flags)
@@ -455,6 +456,10 @@ proc expandObjConstr(c: PContext, n: PNode, t: PType, flags: TExprFlags): PNode
   if hasValue:
     var iterField = 1
     replaceObjConstr(c, t.n, result, iterField, flags)
+    if iterField > result.len:
+      localError(c.config, result.info, "When mixing named fields and unnamed fields, every field needs to be initialized in order")
+    elif iterField < result.len:
+      localError(c.config, result.info, "The object construction is given more fields than required")
 
 proc filterObjConstr(c: PContext; field: PNode, n: PNode, iterField: var int, flags: TExprFlags): bool =
   result = true
@@ -469,19 +474,19 @@ proc filterObjConstr(c: PContext; field: PNode, n: PNode, iterField: var int, fl
         semExprFlagDispatched(c, n[iterField][1], flags + {efPreferStatic})
       else:
         semExprFlagDispatched(c, n[iterField], flags + {efPreferStatic})
-    let oldIterField = iterField
+
     if not filterObjConstr(c, field[0], n, iterField, flags):
       return false
 
-    if iterField > oldIterField:
-      doAssert discriminatorVal != nil and discriminatorVal.kind == nkIntLit # todo error messages
-      let matchedBranch = field.pickCaseBranch discriminatorVal
-      if matchedBranch != nil:
-        result = filterObjConstr(c, matchedBranch.lastSon, n, iterField, flags)
-      else:
-        result = false
+    if discriminatorVal == nil or discriminatorVal.kind != nkIntLit:
+      return false
+
+    let matchedBranch = field.pickCaseBranch discriminatorVal
+    if matchedBranch != nil:
+      result = filterObjConstr(c, matchedBranch.lastSon, n, iterField, flags)
     else:
       result = false
+
   of nkSym:
     if n[iterField].kind != nkExprColonExpr:
       inc iterField
@@ -516,6 +521,11 @@ proc useObjConstr(c: PContext, n: PNode, flags: TExprFlags; expectedType: PType
   if t.kind != tyObject:
     return false
 
+
+  for i in 1..<n.len:
+    if n[i].kind == nkExprColonExpr:
+      return true
+
   var iterField = 1
   result = filterObjConstr(c, t.n, n, iterField, flags)
   if iterField != n.len:

tests/spec/tobjectconstr_unnamed.nim

@@ -4,12 +4,12 @@ type
     b, c: int
 
 block: # positional construction
-  ## It specifies all the unnamed parameters
+  ## It specifies all the unnamed fields
   var x = Vector(1, 2, 3)
   doAssert x.b == 2
 
 block:
-  ## unnamed parameters can be mixed with named parameters
+  ## unnamed fields can be mixed with named fields
   block:
     var x = Vector(a: 1, 2, 3)
     doAssert x.c == 3
@@ -22,14 +22,8 @@ block:
     var x = Vector(1, 2, c: 3)
     doAssert x.c == 3
 
-  block:
-    ## Parameters can be omitted before a named parameter
-    var x = Vector(b: 2, 3)
-    doAssert x.c == 3
-
-
 block:
-  ## Object variants support unnamed parameters for tags, which should be known at the compile time.
+  ## Object variants support unnamed fields for tags, which should be known at the compile time.
   type
     Color = enum
       Red, Blue, Yellow
@@ -72,7 +66,3 @@ block:
   block:
     var x = Ciao(12, flag: true, 1, "123")
     doAssert x.num == 1
-
-  block:
-    var x = Ciao(flag: true, 1, "123")
-    doAssert x.num == 1