use onEnforceFail proc for smaller binaries

Author: timotheecour

lib/std/asserts.nim

@@ -1,19 +1,28 @@
 import system/assertions
 import std/private/miscdollars
 
-template enforce*(cond: untyped, msg: string, typ: typedesc = CatchableError) =
-  ## similar to `doAssert` but defaults to raising `CatchableError` instead of
-  ## `AssertionDefect`, and allows customizing the raised exception type.
+proc onEnforceFail[T](typ: typedesc, prefix: string, arg: T) {.noreturn, noinline.} =
+  ## Making this a proc reduces size of binaries
+  raise newException(typ, prefix & $arg)
+
+template enforce*[T](cond: untyped, arg: T, typ: typedesc = EnforceError) =
+  ## similar to `doAssert` but defaults to raising catchable exception
+  ## instead of `AssertionDefect`, and allows customizing the raised exception type.
+  # `-d:nimLeanMessages` further reduces size of binaries at expense of not
+  # showing location information; in future we can avoid generating un-necessary
+  # strings and forward `TLineInfo` directly (or some equivalent compact type),
+  # and then defer the string rendering until needed in `onEnforceFail`,
+  # reducing binary size while preserving location information. stacktraces
+  # can benefit from the same optimization.
   runnableExamples:
     let a = 1
     enforce a == 1, $(a,)
-    doAssertRaises(CatchableError): enforce a == 2, $(a,)
+    doAssertRaises(EnforceError): enforce a == 2, $(a,)
     doAssertRaises(ValueError): enforce a == 2, $(a,), ValueError
-
-  const
-    loc = instantiationInfo(fullPaths = compileOption("excessiveStackTrace"))
-    ploc = $loc
+  const loc = instantiationInfo(fullPaths = compileOption("excessiveStackTrace"))
   {.line: loc.}:
     if not cond:
-      const expr = astToStr(cond)
-      raise newException(typ, ploc & " `" & expr & "` " & msg)
+      const prefix =
+        when defined(nimLeanMessages): ""
+        else: $loc & " `" & astToStr(cond) & "` "
+      onEnforceFail(typ, prefix, arg)

lib/system/assertions.nim

@@ -83,6 +83,7 @@ template doAssertRaises*(exception: typedesc, code: untyped) =
   const begin = "expected raising '" & astToStr(exception) & "', instead"
   const msgEnd = " by: " & astToStr(code)
   template raisedForeign = raiseAssert(begin & " raised foreign exception" & msgEnd)
+  mixin `$` # for `tests/test_nimscript.nims` (import assertions appears before dollars)
   when Exception is exception:
     try:
       if true:

lib/system/exceptions.nim

@@ -56,6 +56,8 @@ type
 
   CatchableError* = object of Exception ## \
     ## Abstract class for all exceptions that are catchable.
+  EnforceError* = object of Exception ## \
+    ## Default exception raised by `asserts.enforce`.
   IOError* = object of CatchableError ## \
     ## Raised if an IO error occurred.
   EOFError* = object of IOError ## \

tests/stdlib/tasserts.nim

@@ -11,8 +11,11 @@ import std/strutils
 block: ## checks AST isn't transformed as it used to
   let a = 1
   enforce a == 1, $a
+  var raised = false
   try:
     enforce a > 1, $a
-  except CatchableError as e:
-    assert e.msg.endsWith "tasserts.nim(15, 13) `a > 1` 1"
-  doAssertRaises(CatchableError): enforce a > 1, $a
+  except EnforceError as e:
+    raised = true
+    doAssert e.msg.endsWith "tasserts.nim(16, 13) `a > 1` 1"
+  doAssert raised
+  doAssertRaises(EnforceError): enforce a > 1, $a