[Issue 19982] New: padLeft usability issues

[d-bugmail at puremagic.com]

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

          Issue ID: 19982
           Summary: padLeft usability issues
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P1
         Component: phobos
          Assignee: nobody at puremagic.com
          Reporter: sgrammer at economicmodeling.com

padLeft appears to be implicitly converting the input string into an array of
uints. The documentation mentions using byGrapheme, but the compiler can't
handle it.

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import std.range : padLeft;
import std.stdio : writeln;
import std.uni : byGrapheme;
import std.array : array;

void main()
{
    string s = "a string";
    writeln(s.padLeft('0', 10));  // [48, 48, 97, 32, 115, 116, 114, 105, 110,
103]
    writeln("a string".padLeft('0', 10));  // [48, 48, 97, 32, 115, 116, 114,
105, 110, 103]
    writeln("a string".padLeft(dchar('0'), 10));  // "00a string" (correct!)

    // example directly from the documentation
    writeln("abc".padLeft('_', 6));  // [95, 95, 95, 97, 98, 99]

    // Error: template std.range.padLeft cannot deduce function from argument
types !()(Result!string, char, int)
    // writeln(byGrapheme("abc").padLeft('_', 6));

    // Error: template std.range.padLeft cannot deduce function from argument
types !()(Grapheme[], char, int),
    // writeln(byGrapheme("abc").array.padLeft('_', 6));
}

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