implicit conversions in Lua -- what is idiomatic?

[Josh Haberman <jhaberman@...>]

I wanted to hear people's opinions about implicit conversion in Lua.

Say I am exposing to Lua a strongly-typed data structure. It behaves
like a table in many ways, but the set of keys is predefined and each
key as a pre-determined type. So for example:

-- Data structure is: name (string), age (integer)

struct.name = "James"
struct.age = 22

-- Throws "no such field"
struct.doesnt_exist = 5

-- Throws "can't assign string to integer field"
struct.age = "XYZ"

So my first question is, does it seem Lua-like to allow implicit
string <-> integer conversion when it is safe?

-- Auto-convert to "12345" or throw an error?
struct.name = 12345

-- Auto-convert to 22 or throw an error?
struct.age = "22"

Secondly, what is the Lua-like way to handle overflow and truncation?

-- Throw an error or truncate? (assume age is uint32_t)
struct.age = <UINT32_MAX + 1>

-- Throw an error or silently truncate to 22?
struct.age = 22.12345

It appears that luaL_checkinteger() in both Lua 5.2 and Lua 5.3 work1
will silently truncate in this latter case.

Pros of auto conversion/truncation:
- "do what I mean", less typing

Cons of auto conversion/truncation:
- can lead to silent data loss/corruption
- throwing errors might help find bugs sooner

Thoughts? What is the "Lua way" here?