[Help-bash] context sensitive parameter expansion

[Peng Yu]

I have some questions about the design of parameter expansion syntax.

$ echo ${x/a/\"}
"bc
$ echo ${x/a/"}
> ^C

Since " is not used here, why it should be escaped. Based on the
context ${}, it should be clear a double quote should mean a double
quote literally. Wouldn't it be better if " does not have to be
escapped?

$ echo ${x/a/\}}
}bc

This is legitimate, as if } is not escapped, it is not clear whether
it means the end of the parameter expansion.

$ echo ${x/a/\/}
/bc
$ echo ${x/a//}
/bc

Why the last slash is allowed to be escaped (which is equivalent to be
non escaped)? Since there is no point to escape it, isn't that a
syntax error would be better?

$ echo ${x/a/\\}
\bc

-- 
Regards,
Peng