--hintAsError (#16763)

* --hintAsError

* add test, changelog

* condsyms

tests/misc/twarningaserror.nim

@@ -0,0 +1,35 @@
+discard """
+  joinable: false
+"""
+
+#[
+tests: hintAsError, warningAsError
+]#
+
+template fn1 =
+  {.hintAsError[ConvFromXtoItselfNotNeeded]:on.}
+  proc fn(a: string) = discard a.string
+  {.hintAsError[ConvFromXtoItselfNotNeeded]:off.}
+
+template fn2 =
+  {.hintAsError[ConvFromXtoItselfNotNeeded]:on.}
+  proc fn(a: string) = discard a
+  {.hintAsError[ConvFromXtoItselfNotNeeded]:off.}
+
+template gn1 =
+  {.warningAsError[ProveInit]:on.}
+  proc fn(): var int = discard
+  discard fn()
+  {.warningAsError[ProveInit]:off.}
+
+template gn2 =
+  {.warningAsError[ProveInit]:on.}
+  proc fn(): int = discard
+  discard fn()
+  {.warningAsError[ProveInit]:off.}
+
+doAssert not compiles(fn1())
+doAssert compiles(fn2())
+
+doAssert not compiles(gn1())
+doAssert compiles(gn2())