Merge branch 'issue-6805' of https://github.com/Veladus/Nim into Veladus-issue-6805

compiler/ast.nim

@@ -639,7 +639,8 @@ type
     mEqIdent, mEqNimrodNode, mSameNodeType, mGetImpl,
     mNHint, mNWarning, mNError,
     mInstantiationInfo, mGetTypeInfo, mNGenSym,
-    mNimvm, mIntDefine, mStrDefine, mRunnableExamples
+    mNimvm, mIntDefine, mStrDefine, mRunnableExamples,
+    mException
 
 # things that we can evaluate safely at compile time, even if not asked for it:
 const

compiler/semstmts.nim

@@ -729,6 +729,16 @@ proc semRaise(c: PContext, n: PNode): PNode =
     var typ = n.sons[0].typ
     if typ.kind != tyRef or typ.lastSon.kind != tyObject:
       localError(n.info, errExprCannotBeRaised)
+    
+    # check if the given object inherits from Exception
+    var base = typ.lastSon
+    while true:
+      if base.sym.magic == mException:
+        break
+      if base.lastSon == nil:
+        localError(n.info, "raised object of type $1 does not inherit from Exception", [typ.sym.name.s])
+        return
+      base = base.lastSon
 
 proc addGenericParamListToScope(c: PContext, n: PNode) =
   if n.kind != nkGenericParams: illFormedAst(n)

lib/system.nim

@@ -463,7 +463,7 @@ type
     line*: int          ## line number of the proc that is currently executing
     filename*: cstring  ## filename of the proc that is currently executing
 
-  Exception* {.compilerproc.} = object of RootObj ## \
+  Exception* {.compilerproc, magic: "Exception".} = object of RootObj ## \
     ## Base exception class.
     ##
     ## Each exception has to inherit from `Exception`. See the full `exception