Added more tests to toverflw

tests/overflw/toverflw.nim

@@ -1,21 +1,84 @@
 discard """
   file: "toverflw.nim"
-  output: "the computation overflowed"
+  output: "ok"
+  cmd: "nim $target -d:release $options $file"
+
 """
 # Tests nim's ability to detect overflows
 
 {.push overflowChecks: on.}
 
 var
-  a, b: int
+  a = high(int)
-a = high(int)
+  b = -2
-b = -2
+  overflowDetected = false
+
 try:
   writeLine(stdout, b - a)
 except OverflowError:
-  writeLine(stdout, "the computation overflowed")
+  overflowDetected = true
 
 {.pop.} # overflow check
-#OUT the computation overflowed
+
+doAssert(overflowDetected)
+
+block: # Overflow checks in a proc
+  var
+    a = high(int)
+    b = -2
+    overflowDetected = false
+
+  {.push overflowChecks: on.}
+  proc foo() =
+    let c = b - a
+  {.pop.}
+
+  try:
+    foo()
+  except OverflowError:
+    overflowDetected = true
+
+  doAssert(overflowDetected)
+
+block: # Overflow checks in a forward declared proc
+  var
+    a = high(int)
+    b = -2
+    overflowDetected = false
+
+  proc foo()
+
+  {.push overflowChecks: on.}
+  proc foo() =
+    let c = b - a
+  {.pop.}
+
+  try:
+    foo()
+  except OverflowError:
+    overflowDetected = true
+
+  doAssert(overflowDetected)
+
+block: # Overflow checks doesn't affect fwd declaration
+  var
+    a = high(int)
+    b = -2
+    overflowDetected = false
+
+  {.push overflowChecks: on.}
+  proc foo()
+  {.pop.}
+
+  proc foo() =
+    let c = b - a
+
+  try:
+    foo()
+  except OverflowError:
+    overflowDetected = true
+
+  doAssert(not overflowDetected)
 
 
+echo "ok"