REG 1.42.0-beta1: Obj-C related compile error on Linux and misleading error location

[s-ludwig]

Receiving the following error on Linux that doesn't occur for 1.41.0:

app-desktop/source/krtek/desktop/gui/panes/metadata.d(618,55): Error: Runtime function `objc_opt_isKindOfClass` was not found
                            auto btn = cast(ListIconButton)tsi.extraWidgets[0];
                                                                           ^

The location associated with the error does not have anything to do with extern (Objective-C), but there are other parts of the code base that do call Objective-C functions, but obviously only when compiling for Apple platforms. AFAICS, all such code is in version (iOS) or version (OSX) blocks.

[LunaTheFoxgirl]

This issue is related to this
#5034

So it affects more than just TypeInfo.

[s-ludwig]

Finally got a reduced case, unfortunately import std; is part of it.

source/test.d

import imp;

class MetadataPane : Widget {
	void updateUI()
	{
		TreeSheetItem getTreeSheetItem() {
			return null;
		}

		if (auto tsi = getTreeSheetItem) cast(ListIconButton)tsi.extraWidgets[0];
	}
}

import/imp.d

import std;

class TreeItem {
	struct ExtraWidget { Widget widget; }
	ExtraWidget[] m_extraWidgets;
	@property extraWidgets() { return m_extraWidgets.map!(w => w.widget); }
}

class ListIconButton {}

class TreeSheetItem : TreeItem {}

class Widget {}

Compile as ldc2 -Iimport source/test.d

edit: replaced test.zip by inline code

[kinke]

Thx! Reduced further:

class C {}
class D {}
struct S { D d; }

C foo(S[] ss) {
    import std.algorithm;
    return cast(C) (ss.map!(s => s.d)[0]);
}

With a local build, I hit this:

ldc/gen/classes.cpp

Line 381 in 2e9f5be

llvm_unreachable("dynamic cast should have been lowered");

It works without the temporary:

    auto d = ss.map!(s => s.d)[0];
    return cast(C) d;

So looks like an oversight for the new lowering in the frontend.

[kinke]

The problem is:

ldc/dmd/expressionsem.d

Lines 10063 to 10066 in 2e9f5be

	if (auto cex = ex.isCastExp())
	{
	lowerCastExp(cex, sc);
	}

For the testcase, the original CastExp is cast(C)((MapResult!(__lambda_L11_C33, S[]) __dop111 = map(ss);) , __dop111.opIndex(0LU)), which gets converted to (MapResult!(__lambda_L11_C33, S[]) __dop111 = map(ss);) , cast(C)__dop111.opIndex(0LU) in

ldc/dmd/expressionsem.d

Line 9959 in 2e9f5be

Expression ex = exp.e1.castTo(sc, exp.to);

[kinke]

Filed dlang/dmd#22422, with a testcase that fails with DMD too (at runtime).

[kinke]

The upstream fix has landed in master here.

[s-ludwig]

Just tested master and everything works fine now. Thank you for the quick diagnosis and fix implementation!

@LunaTheFoxgirl did this also fix #5034?

[LunaTheFoxgirl]

Currently sick with a nasty parasite, but I'll check once I feel better