Compiler now catches when an expression is raised which is no Exception

compiler/msgs.nim

@@ -61,7 +61,7 @@ type
     errBaseTypeMustBeOrdinal, errInheritanceOnlyWithNonFinalObjects,
     errInheritanceOnlyWithEnums, errIllegalRecursionInTypeX,
     errCannotInstantiateX, errExprHasNoAddress, errXStackEscape,
-    errVarForOutParamNeededX,
+    errVarForOutParamNeededX, errExprIsNoException,
     errPureTypeMismatch, errTypeMismatch, errButExpected, errButExpectedX,
     errAmbiguousCallXYZ, errWrongNumberOfArguments,
     errWrongNumberOfArgumentsInCall,
@@ -269,6 +269,7 @@ const
     errExprHasNoAddress: "expression has no address",
     errXStackEscape: "address of '$1' may not escape its stack frame",
     errVarForOutParamNeededX: "for a \'var\' type a variable needs to be passed; but '$1' is immutable",
+    errExprIsNoException: "raised object does not inherit from Exception",
     errPureTypeMismatch: "type mismatch",
     errTypeMismatch: "type mismatch: got (",
     errButExpected: "but expected one of: ",

compiler/semstmts.nim

@@ -721,6 +721,8 @@ proc semFor(c: PContext, n: PNode): PNode =
     result.typ = enforceVoidContext
   closeScope(c)
 
+var exceptionID = -1
+
 proc semRaise(c: PContext, n: PNode): PNode =
   result = n
   checkSonsLen(n, 1)
@@ -729,6 +731,20 @@ 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 exceptionID == -1:
+        if base.sym.name.s == "Exception":
+          exceptionID = base.id
+          break
+      elif base.id == exceptionID:
+        break
+      if base.lastSon == nil:
+        localError(n.info, errExprIsNoException)
+        return
+      base = base.lastSon
 
 proc addGenericParamListToScope(c: PContext, n: PNode) =
   if n.kind != nkGenericParams: illFormedAst(n)