[Issue 14035] string concatenation accepts ints in templates

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=14035

--- Comment #6 from yebblies <yebblies at gmail.com> ---
The type of ln doesn't change.

The template expands to something like

enum uint ln = 4;
enum alice = "{ int t_"~ln~" = 42; }";

As the compiler knows the _value_ for ln, it expands alice's initializer to
enum alice = "{ int t_"~4~" = 42; }";

Then, because it knows that 4 can fit in a char, it allows it to become this:

enum alice = "{ int t_"~cast(char)4~" = 42; }";

And then the concatenation is semantically valid.

As I said in my first comment, range propagation is allowed so that code like
this will still work:

enum str = "abc" ~ ('a' + 7);

Here ('a' + 7) has type int, but because we know the value at compile time and
know it will fit in a char, it is allowed to be narrowed.

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