fixes #25116; default(T) breaks requiresInit requirements

compiler/sem.nim

@@ -710,10 +710,7 @@ proc defaultNodeField(c: PContext, a: PNode, aTyp: PType, checkDefault: bool): P
     else:
       result = nil
   of tyRange:
-    if c.graph.config.isDefined("nimPreviewRangeDefault"):
-      result = firstRange(c.config, aTypSkip)
-    else:
-      result = nil
+    result = firstRange(c.config, aTypSkip)
   else:
     result = nil
 

compiler/semmagic.nim

@@ -580,12 +580,18 @@ proc semPrivateAccess(c: PContext, n: PNode): PNode =
     c.currentScope.allowPrivateAccess.add t.sym
   result = newNodeIT(nkEmpty, n.info, getSysType(c.graph, n.info, tyVoid))
 
-proc checkDefault(c: PContext, n: PNode): PNode =
+proc checkDefault(c: PContext, n: PNode; isDefault: bool): PNode =
   result = n
   c.config.internalAssert result[1].typ.kind == tyTypeDesc
   let constructed = result[1].typ.base
-  if constructed.requiresInit:
-    message(c.config, n.info, warnUnsafeDefault, typeToString(constructed))
+  # allows simple range types because they now have a valid default value
+  if constructed.requiresInit and constructed.skipTypes({tyGenericInst}).kind != tyRange:
+    # TODO: sorts out `nimPreviewRangeDefault` with `ranges` in the future
+    # TODO: be lenient with views and notnil types for now
+    if isDefault and c.config.features * {views, notnil} == {}:
+      localError(c.config, n.info, "The '$1' type doesn't have a valid default value" % typeToString(constructed))
+    else:
+      message(c.config, n.info, warnUnsafeDefault, typeToString(constructed))
 
 proc magicsAfterOverloadResolution(c: PContext, n: PNode,
                                    flags: TExprFlags; expectedType: PType = nil): PNode =
@@ -672,16 +678,18 @@ proc magicsAfterOverloadResolution(c: PContext, n: PNode,
     let seqType = result[1].typ.skipTypes({tyPtr, tyRef, # in case we had auto-dereferencing
                                            tyVar, tyGenericInst, tyOwned, tySink,
                                            tyAlias, tyUserTypeClassInst})
-    if seqType.kind == tySequence and seqType.base.requiresInit:
+    if seqType.kind == tySequence and seqType.base.requiresInit and
+        seqType.base.skipTypes({tyGenericInst}).kind != tyRange:
+      # allows simple range types because they now have a valid default value
       message(c.config, n.info, warnUnsafeSetLen, typeToString(seqType.base))
   of mDefault:
-    result = checkDefault(c, n)
+    result = checkDefault(c, n, true)
     let typ = result[^1].typ.skipTypes({tyTypeDesc})
     let defaultExpr = defaultNodeField(c, result[^1], typ, false)
     if defaultExpr != nil:
       result = defaultExpr
   of mZeroDefault:
-    result = checkDefault(c, n)
+    result = checkDefault(c, n, false)
   of mIsolate:
     if not checkIsolate(n[1]):
       localError(c.config, n.info, "expression cannot be isolated: " & $n[1])

tests/errmsgs/t25116.nim

@@ -0,0 +1,9 @@
+discard """
+  errormsg: "The 'RI' type doesn't have a valid default value"
+"""
+
+
+type RI {.requiresInit.} = object
+  v: int
+
+var v = default(RI) # should be flagged as invalid