Bug 18472 – [Reg 2.078] betterC: cannot use format at compile time.

import std.format; import std.stdio; void main() { enum s = "%1$s,%2$s".format("foo","bar"); writeln(s); } fails with /dlang/dmd-nightly/linux/bin64/../../src/phobos/std/array.d(2889): Error: TypeInfo cannot be used with -betterC due to the use of Appender at line 2889 is `private struct Data` This did use to work as I have always compiled Dcompute with -betterC, however upgrading to LDC 1.8.0b1 based on v2.078.2 (from LDC master in about December), I hit #18101, and trying run.dlang.io to see how soon it would get fixed and hit this.

The test doesn't compile with 2.078.3. 2.078.3 does not include the TypeInfo check, so at most this is a diagnostic regression. https://run.dlang.io/is/fvj8jb /dlang/dmd/linux/bin64/../../src/phobos/std/range/primitives.d(405): Error: static assert "Cannot put a const(char)[] into a Appender!string." /dlang/dmd/linux/bin64/../../src/phobos/std/format.d(1172): instantiated from here: put!(Appender!string, const(char)[]) /dlang/dmd/linux/bin64/../../src/phobos/std/format.d(473): instantiated from here: writeUpToNextSpec!(Appender!string) /dlang/dmd/linux/bin64/../../src/phobos/std/format.d(5831): instantiated from here: formattedWrite!(Appender!string, char, string, string) onlineapp.d(5): instantiated from here: format!(char, string, string) Do you have a test that will demonstrate a successful build prior to the TypeInfo check introduced in 2.079?

cat > bug.d << CODE import std.format; import std.stdio; void main() { enum s = "%1$s,%2$s".format("foo","bar"); writeln(s); } CODE dmd -c -betterC bug.d ---- /home/dawg/dlang/dmd-2.078.0/linux/bin64/../../src/phobos/std/range/primitives.d(405): Error: static assert "Cannot put a const(char)[] into a Appender!string." /home/dawg/dlang/dmd-2.078.0/linux/bin64/../../src/phobos/std/format.d(1172): instantiated from here: put!(Appender!string, const(char)[]) /home/dawg/dlang/dmd-2.078.0/linux/bin64/../../src/phobos/std/format.d(473): instantiated from here: writeUpToNextSpec!(Appender!string) /home/dawg/dlang/dmd-2.078.0/linux/bin64/../../src/phobos/std/format.d(5831): instantiated from here: formattedWrite!(Appender!string, char, string, string) /home/dawg/Code/D/bug.d(5): instantiated from here: format!(char, string, string) ---- Confirmed that this stopped to work with 2.078.0, the error looks rather weird, as betterC shouldn't change types. Also indeed with 2.079.0-beta.1 the error message is now about using TypeInfo. ---- /home/dawg/dlang/dmd-2.079.0-beta.1/linux/bin64/../../src/phobos/std/array.d(2889): Error: TypeInfo cannot be used with -betterC ---- The test case compiles fine with 2.077.1.

(In reply to Martin Nowak from comment #2) > cat > bug.d << CODE > import std.format; > import std.stdio; > void main() > { > enum s = "%1$s,%2$s".format("foo","bar"); > writeln(s); > } > CODE > dmd -c -betterC bug.d > ---- > /home/dawg/dlang/dmd-2.078.0/linux/bin64/../../src/phobos/std/range/ > primitives.d(405): Error: static assert "Cannot put a const(char)[] into a > Appender!string." > /home/dawg/dlang/dmd-2.078.0/linux/bin64/../../src/phobos/std/format.d(1172): > instantiated from here: put!(Appender!string, const(char)[]) > /home/dawg/dlang/dmd-2.078.0/linux/bin64/../../src/phobos/std/format.d(473): > instantiated from here: writeUpToNextSpec!(Appender!string) > /home/dawg/dlang/dmd-2.078.0/linux/bin64/../../src/phobos/std/format.d(5831): > instantiated from here: formattedWrite!(Appender!string, char, string, > string) > /home/dawg/Code/D/bug.d(5): instantiated from here: format!(char, > string, string) > ---- > > Confirmed that this stopped to work with 2.078.0, the error looks rather > weird, as betterC shouldn't change types. > Indeed that is issue 18101 which was fixed to check typeinfo, but now also fails at compile time. > Also indeed with 2.079.0-beta.1 the error message is now about using > TypeInfo. > ---- > /home/dawg/dlang/dmd-2.079.0-beta.1/linux/bin64/../../src/phobos/std/array. > d(2889): Error: TypeInfo cannot be used with -betterC > ---- > > The test case compiles fine with 2.077.1. That sounds about the right timeframe.

Isn't this then a duplicate of Issue 18101? In other words, if Issue 18101 were solved, there wouldn't be a need for TypeInfo, and therefore the TypeInfo error would not be triggered?

Here's a simpler test case: module betterc; enum b = typeid(size_t) is typeid(uint); >dmd -betterC -c betterc.d betterc.d(2): Error: TypeInfo cannot be used with -betterC

(In reply to Rainer Schuetze from comment #5) > Here's a simpler test case: > > module betterc; > enum b = typeid(size_t) is typeid(uint); At https://dlang.org/spec/betterc.html under the "Not Available" section: > 2. TypeInfo and ModuleInfo So, it is by design that any call to `typeid` is going to fail when compiled with `-betterC`. This specific issue is about not being able to use `format` in `-betterC`. Perhaps the reason for that is because `format` relies on runtime type information (i.e. TypeInfo). So the solution, specific to this issue, would not be allow uses of `typeid` in `-betterC`, but rather to remove the dependency of `format` on runtime type information (if that's even possible). D has excellent facilities for doing introspection at compile-time, so it may be possible to look to those facilities in concert with templates to find a solution that does not rely on runtime type information. It would likely also help to begin replacing compiler-generated calls to runtime hooks that depend on `TypeInfo` with templates. See also https://forum.dlang.org/post/[email protected]

I think the main issue is that the compiler does not distinguish between information needed at compile time and what's necessary inside the object file.

(In reply to Rainer Schuetze from comment #7) > I think the main issue is that the compiler does not distinguish between > information needed at compile time and what's necessary inside the object > file. Ok, I understand now: `enum b = typeid(size_t) is typeid(uint);` should be evaluated at compile time, and I the -betterC limitations should only apply at runtime.

Working on a fix at https://github.com/dlang/dmd/pull/8173

PR 8173 seems to take care of the case... module betterc; enum b = typeid(size_t) is typeid(uint) ... but still fails for ... import std.format; import std.stdio; void main() { enum s = "%1$s,%2$s".format("foo","bar"); writeln(s); } ... with the same TypeInfo error. However, if I comment out the TypeInfo check altogether, the `format` test case fails with... phobos/std/range/primitives.d(405): Error: static assert: "Cannot put a const(char)[] into a Appender!string." phobos/std/format.d(1184): instantiated from here: put!(Appender!string, const(char)[]) /phobos/std/format.d(473): instantiated from here: writeUpToNextSpec!(Appender!string) phobos/std/format.d(6168): instantiated from here: formattedWrite!(Appender!string, char, string, string) main.d(5): instantiated from here: format!(char, string, string) I'm wondering if there was another change to Phobos around the same time frame was the TypeInfo change that prevents the `format` expression from evaluating at compile-time.

Commits pushed to master at https://github.com/dlang/dmd https://github.com/dlang/dmd/commit/cb2b0b848a1c6a2b208ba12257f6204c725744e4 Partial fix for Issue 18472 - permit using typeid at compile-time in betterC https://github.com/dlang/dmd/commit/a402a791694df063d8bd7a5b9d2f6651e9185cee Merge pull request #8173 from JinShil/fix_18472 Partial fix for Issue 18472 - permit using typeid at compile-time in betterC merged-on-behalf-of: Jacob Carlborg <[email protected]>

This appears to work now in nightly: import std.format; import std.stdio; void main() { enum s = "%1$s,%2$s".format("foo","bar"); writeln(s); } https://run.dlang.io/is/BDyoHF It may have been fixed inadvertently by https://github.com/dlang/dmd/pull/8523

(In reply to Mike Franklin from comment #12) > This appears to work now in nightly: > > import std.format; > import std.stdio; > void main() > { > enum s = "%1$s,%2$s".format("foo","bar"); > writeln(s); > } > > https://run.dlang.io/is/BDyoHF > > It may have been fixed inadvertently by > https://github.com/dlang/dmd/pull/8523 Gah, scratch that. Forgot to add the -betterC flag. :-(

A bounty has been set on this issue: https://www.flipcause.com/secure/cause_pdetails/NjU3MTQ=

@etcimon updated dlang/dmd pull request #14676 "Fix 18472: betterC cannot use format at compile time." fixing this issue: - Fix 18472: betterC cannot use format at compile time. https://github.com/dlang/dmd/pull/14676

@WalterBright created dlang/dmd pull request #14930 "fix Issue 18472: betterC cannot use format at compile time" fixing this issue: - fix Issue 18472: betterC cannot use format at compile time https://github.com/dlang/dmd/pull/14930

dlang/dmd pull request #14930 "fix Issue 18472: betterC cannot use format at compile time" was merged into master: - 116d35134cc17fc06fc4b3ad1ed9af65b44e7d39 by Walter Bright: fix Issue 18472: betterC cannot use format at compile time https://github.com/dlang/dmd/pull/14930

Continued with https://issues.dlang.org/show_bug.cgi?id=23754 as a Phobos bug.