3 files changed, 18 insertions, 12 deletions
diff --git a/compiler/guards.nim b/compiler/guards.nim
index d8441c544..8d271fa6d 100644
--- a/compiler/guards.nim
+++ b/compiler/guards.nim
@@ -187,7 +187,8 @@ proc usefulFact(n: PNode): PNode =
     #   if a:
     #     ...
     # We make can easily replace 'a' by '2 < x' here:
-    result = usefulFact(n.sym.ast)
+    if n.sym.ast != nil:
+      result = usefulFact(n.sym.ast)
   elif n.kind == nkStmtListExpr:
     result = usefulFact(n.lastSon)
 
diff --git a/compiler/sem.nim b/compiler/sem.nim
index bcdfc7939..4396a9093 100644
--- a/compiler/sem.nim
+++ b/compiler/sem.nim
@@ -141,22 +141,24 @@ proc semDirectOp(c: PContext, n: PNode, flags: TExprFlags): PNode
 
 proc semWhen(c: PContext, n: PNode, semCheck: bool = true): PNode
 
-proc evalTypedExpr(c: PContext, e: PNode): PNode =
+proc semConstExpr(c: PContext, n: PNode): PNode =
+  var e = semExprWithType(c, n)
+  if e == nil:
+    LocalError(n.info, errConstExprExpected)
+    return n
   result = getConstExpr(c.module, e)
   if result == nil:
     result = evalConstExpr(c.module, e)
     if result == nil or result.kind == nkEmpty:
-      LocalError(e.info, errConstExprExpected)
+      if e.info != n.info:
+        pushInfoContext(n.info)
+        LocalError(e.info, errConstExprExpected)
+        popInfoContext()
+      else:
+        LocalError(e.info, errConstExprExpected)
       # error correction:
       result = e
 
-proc semConstExpr(c: PContext, n: PNode): PNode =
-  var e = semExprWithType(c, n)
-  if e == nil:
-    LocalError(n.info, errConstExprExpected)
-    return n
-  result = evalTypedExpr(c, e)
-
 include hlo, seminst, semcall
 
 proc symFromType(t: PType, info: TLineInfo): PSym =
diff --git a/compiler/semexprs.nim b/compiler/semexprs.nim
index 28ea50a15..a524e71da 100644
--- a/compiler/semexprs.nim
+++ b/compiler/semexprs.nim
@@ -751,8 +751,11 @@ proc semEcho(c: PContext, n: PNode): PNode =
   checkMinSonsLen(n, 1)
   for i in countup(1, sonsLen(n) - 1): 
     var arg = semExprWithType(c, n.sons[i])
-    n.sons[i] = semExpr(c, buildStringify(c, arg))
-  
+    n.sons[i] = semExprWithType(c, buildStringify(c, arg))
+    let t = n.sons[i].typ
+    if t == nil or t.skipTypes(abstractInst).kind != tyString:  
+      LocalError(n.info, errGenerated,
+                 "implicitly invoked '$' does not return string")
   let t = n.sons[0].typ
   if tfNoSideEffect notin t.flags: incl(c.p.owner.flags, sfSideEffect)
   result = n