Why can't the compiler properly detect the type of Array!string("something")?

[Adnan]

On Sunday, 15 March 2020 at 00:04:09 UTC, Adnan wrote:
> On Saturday, 14 March 2020 at 23:54:44 UTC, Adam D. Ruppe wrote:
>> On Saturday, 14 March 2020 at 23:39:11 UTC, Adnan wrote:
>>> Full code
>>
>> this worked for me when i copy/pasted it... are you sure that 
>> has the error? if so what compiler version you on?
>
> This is indeed very strange, godbolt says it's alright: 
> https://d.godbolt.org/z/DaaPxX
>
> Now my compiler version:
> $ dmd --version && ldc2 --version
> DMD64 D Compiler v2.090.0
> Copyright (C) 1999-2019 by The D Language Foundation, All 
> Rights Reserved written by Walter Bright
> LDC - the LLVM D compiler (1.18.0):
>   based on DMD v2.088.1 and LLVM 9.0.0
>   built with LDC - the LLVM D compiler (1.18.0)
>   Default target: x86_64-unknown-linux-gnu
>   Host CPU: znver1
>   http://dlang.org - http://wiki.dlang.org/LDC
>
>   Registered Targets:
>     aarch64    - AArch64 (little endian)
>     aarch64_32 - AArch64 (little endian ILP32)
>     aarch64_be - AArch64 (big endian)
>     arm        - ARM
>     arm64      - ARM64 (little endian)
>     arm64_32   - ARM64 (little endian ILP32)
>     armeb      - ARM (big endian)
>     mips       - MIPS (32-bit big endian)
>     mips64     - MIPS (64-bit big endian)
>     mips64el   - MIPS (64-bit little endian)
>     mipsel     - MIPS (32-bit little endian)
>     msp430     - MSP430 [experimental]
>     nvptx      - NVIDIA PTX 32-bit
>     nvptx64    - NVIDIA PTX 64-bit
>     ppc32      - PowerPC 32
>     ppc64      - PowerPC 64
>     ppc64le    - PowerPC 64 LE
>     riscv32    - 32-bit RISC-V
>     riscv64    - 64-bit RISC-V
>     thumb      - Thumb
>     thumbeb    - Thumb (big endian)
>     wasm32     - WebAssembly 32-bit
>     wasm64     - WebAssembly 64-bit
>     x86        - 32-bit X86: Pentium-Pro and above
>     x86-64     - 64-bit X86: EM64T and AMD64
>
>
> Note that both ldc2 and dmd has the same complain

d$ dmd --version && cat source/app.d && dub build
DMD64 D Compiler v2.090.0
Copyright (C) 1999-2019 by The D Language Foundation, All Rights 
Reserved written by Walter Bright
string smallestRepr(const string arg) {
	auto repeated = arg ~ arg;
	string result = arg;
	foreach (i; 1 .. arg.length) {
		const slice = repeated[i .. i + arg.length];
		if (slice < result)
			result = slice;
	}
	return result;
}

unittest {
	assert("cba".smallestRepr() == "acb");
}

void main(const string[] args) {
	import std.stdio : write, File;
	import std.container : Array;

	Array!string[string] wordTable;

	foreach (string word; File(args[1]).byLineCopy()) {
		word = word[0 .. $ - 1]; // strip the newline character
		const string key = word.smallestRepr();
		debug {
			if (key in wordTable)
				wordTable[key] ~= word;
			else
				wordTable[key] = Array!string(word);
		}
		else {
			wordTable.require(key, Array!string()) ~= word;
		}
	}

	foreach (array; wordTable.values) {
		if (array.length == 4) {
			foreach (word; array) {
				write(word, ", ");
			}
			write("\n");
			break;
		}
	}
}
Performing "debug" build using dmd for x86_64.
dbed ~master: building configuration "application"...
source/app.d(29,34): Error: template 
std.container.array.Array!string.Array.__ctor cannot deduce 
function from argument types !()(string), candidates are:
/snap/dmd/99/bin/../import/phobos/std/container/array.d(467,5):   
      __ctor(U)(U[] values...)
   with U = immutable(char)
   must satisfy the following constraint:
        isImplicitlyConvertible!(U, T)
/snap/dmd/99/bin/../import/phobos/std/container/array.d(501,5):   
      __ctor(Range)(Range r)
   with Range = string
   must satisfy the following constraint:
        isImplicitlyConvertible!(ElementType!Range, T)
source/app.d(36,2): Warning: statement is not reachable
dmd failed with exit code 1.