Rely on implicit coercion (where makes sense) when coercing arguments

[medikoo]

Currently in some places to normalize arguments we rely on explicit coercion (e.g. String(str)), when it's more accurate to ensure implicit coercion (e.g. +str).

Thing is there are some intentional differences between those two coercion mechanism, and when validating arguments the implicit coercion characteristics should be ensured.