[Issue 19125] New: IFTI and inout removes head mutability qualifier on by-val parameters

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=19125

          Issue ID: 19125
           Summary: IFTI and inout removes head mutability qualifier on
                    by-val parameters
           Product: D
           Version: D2
          Hardware: x86
                OS: Mac OS X
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: ali.akhtarzada at gmail.com

>From here: https://forum.dlang.org/post/jxcohrtxsfkechfgwrgo@forum.dlang.org


import std.stdio;

struct W(T) {
    T t;
}
auto wrap0(T)(auto ref inout(T) t) {
    return inout(W!T)(t);
}
auto wrap1(T)(auto ref inout(T) t) {
    return t;
}
void main() {
    pragma(msg, typeof(wrap0("foo"))); // removes it
    pragma(msg, typeof(wrap1("bar"))); // keeps it
    immutable int i0;
    pragma(msg, typeof(wrap1(i0))); // keeps it
    string s0 = "baz";
    pragma(msg, typeof(wrap0(s0))); // keeps it
}

prints:

immutable(W!(char[]))
immutable(string)
immutable(int)
W!string

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