[Issue 19982] padLeft usability issues

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=19982

--- Comment #4 from shove <shove at 163.com> ---
The final step in the internal implementation of padLeft is chain() , and
chain() converts multiple different types into a single type that can be
accommodated via CommonType.

alias X = CommonType!(int, long, short);
assert(is(X == long));
alias Y = CommonType!(int, char[], short);
assert(is(Y == void));

--------------------------

static assert(is(ElementType!(typeof("string".padLeft('0', 10))) == uint));
static assert(is(ElementType!(typeof("string".padLeft(dchar('0'), 10))) ==
dchar));

The corresponding types of these two sentences are transformed as follows:

alias Z1 = CommonType!(char, dchar);
static assert(is(Z1 == uint));
alias Z2 = CommonType!(dchar, dchar);
static assert(is(Z2 == dchar));


So there is no problem with the design here, we can use it flexibly after
mastering this feature.

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