assert unittest doesn't respect assertThrown (correction)

[Brother Bill]

On Tuesday, 20 January 2026 at 20:42:21 UTC, Brother Bill wrote:
> In a unittest, we have assertThrown average([1], [1, 2]));
> As assert statement throws an exception.
> But the unittest fails, which seems odd, as an assert did throw.
> Have I found another bug in DMD?
>
> ```
> import std.stdio : writeln;
> import std.exception : enforce, assertThrown, assertNotThrown;
>
> void main()
> {
> 	auto result = average([], []);
>
> 	// assert is not caught in catch block
> 	// enforce is caught in catch block
> 	try
> 	{
> 		result = average([1], [1, 2]);
> 	}
> 	catch (Exception e)
> 	{
> 		writeln("Caught exception: ", e.msg);
> 	}	
> }
>
> int[] average(int[] a, int[] b)
> {
> 	assert( a.length == b.length, "assert:  Input slices must have 
> the same length");	// assert  will not be caught in catch block
> 	// enforce(a.length == b.length, "enforce: Input slices must 
> have the same length");	// enforce will     be caught in catch 
> block
>
> 	// Implementation goes here
> 	return cast(int[])[]; // Initial result, so it compiles
> }
>
> unittest
> {
> 	/* Must throw for uneven slices */
> 	assertThrown(average([1], [1, 2]));
>
> 	/* Must not throw for empty slices */
> 	assertNotThrown(average([], []));
> }
> ```
>
> Running it in Linux Terminal
> ```
> bb at fedora:~/temp/c42_p217_6a_testing_for_exceptions$ dub test 
> --force    # with assert only
>              No source files found in configuration 'library'. 
> Falling back to default configuration for test runner.
>     Starting Performing "unittest" build using /usr/bin/dmd for 
> x86_64.
>     Building c42_6a_testing_for_exceptions ~master: building 
> configuration [application]
>      Linking c42_6a_testing_for_exceptions
>      Running c42_6a_testing_for_exceptions
> core.exception.AssertError at source/app.d(22): assert:  Input 
> slices must have the same length
> ----------------
> ??:? _d_assert_msg [0x40301c]
> source/app.d:22 int[] app.average(int[], int[]) [0x400d6e]
> source/app.d:32 pure @safe int[] 
> app.__unittest_L29_C1().__dgliteral_L32_C22() [0x400e46]
> /usr/include/dmd/phobos/std/exception.d:294 pure nothrow @safe 
> void std.exception.assertThrown!(Exception, 
> int[]).assertThrown(lazy int[], immutable(char)[], 
> immutable(char)[], ulong) [0x4025b2]
> source/app.d:32 void app.__unittest_L29_C1() [0x400daf]
> ??:? void app.__modtest() [0x402cbc]
> ??:? int 
> core.runtime.runModuleUnitTests().__foreachbody_L603_C5(object.ModuleInfo*) [0x40c52e]
> ??:? int object.ModuleInfo.opApply(scope int 
> delegate(object.ModuleInfo*)).__lambda_L2519_C13(immutable(object.ModuleInfo*)) [0x40a087]
> ??:? int rt.minfo.moduleinfos_apply(scope int 
> delegate(immutable(object.ModuleInfo*))).__foreachbody_L585_C5(ref rt.sections_elf_shared.DSO) [0x412593]
> ??:? int rt.sections_elf_shared.DSO.opApply(scope int 
> delegate(ref rt.sections_elf_shared.DSO)) [0x412be5]
> ??:? int rt.minfo.moduleinfos_apply(scope int 
> delegate(immutable(object.ModuleInfo*))) [0x412521]
> ??:? int object.ModuleInfo.opApply(scope int 
> delegate(object.ModuleInfo*)) [0x40a059]
> ??:? runModuleUnitTests [0x40c363]
> ??:? void rt.dmain2._d_run_main2(char[][], ulong, extern (C) 
> int function(char[][])*).runAll() [0x403c0c]
> ??:? void rt.dmain2._d_run_main2(char[][], ulong, extern (C) 
> int function(char[][])*).tryExec(scope void delegate()) 
> [0x403b99]
> ??:? _d_run_main2 [0x403b0f]
> ??:? _d_run_main [0x403917]
> /usr/include/dmd/druntime/import/core/internal/entrypoint.d:29 
> main [0x400e99]
> ??:? [0x7f80e860f5b4]
> ??:? __libc_start_main [0x7f80e860f667]
> ??:? _start [0x400b64]
> 1/1 modules FAILED unittests
> Error Program exited with code 1
> ```