Bug 19691 – ICE on null default value for struct parameter in constructor

This code: struct S1 { this(T...)(T) { S2(""); } } struct S2 { this(string) {} this(S1 s = null) {} } Crashes the compiler (2.084.1). I've not been able to reduce it to a simple overload problem. That is, this does not exhibit the same issue: struct S1 { this(T...)(T) { fun(""); } } void fun(S1 s = null) {} void fun(string s) {}

That's a regression, 2.075.z: https://run.dlang.io/is/vqQyCh - The bug doesn't happen if you change the order of declaration, i.e S2 before S1 - The bug happens because of a null scope: Program received signal SIGSEGV, Segmentation fault. 0x00000000005b6a01 in DsymbolSemanticVisitor::visit(CtorDeclaration*) (this=0x7fffffff97b0, ctd=0x7ffff6d46370) at dmd/dsymbolsem.d:3708 3708 ctd.parent = sc.parent; Missing separate debuginfos, use: dnf debuginfo-install libgcc-8.2.1-6.fc28.x86_64 (gdb) (gdb) bt #0 0x00000000005b6a01 in DsymbolSemanticVisitor::visit(CtorDeclaration*) (this=0x7fffffff97b0, ctd=0x7ffff6d46370) at dmd/dsymbolsem.d:3708 #1 0x000000000060fdf2 in CtorDeclaration::accept(Visitor*) (this=0x7ffff6d46370, v=0x7fffffff97b0) at dmd/func.d:3373 #2 0x00000000005ac291 in dsymbolSemantic(Dsymbol*, Scope*) (dsym=0x7ffff6d46370, sc=0x0) <--- here, null scope at dmd/dsymbolsem.d:365 #3 0x00000000005c345d in _D3dmd9dtemplate15functionResolveFPSQBi11declaration5MatchCQCf7dsymbol7DsymbolSQCz7globals3LocPSQDq6dscope5ScopePSQEi4root5array__T5ArrayTCQFhQz10rootobject10RootObjectZQBmCQGp5mtype4TypePSQHfQCxQCv__TQCsTCQHw10expression10ExpressionZQDzPPxaZ13applyFunctionMFCQJy4func15FuncDeclarationZi (__capture=0x7fffffff9a00, fd=0x7ffff6d46370) at dmd/dtemplate.d:2411 #4 0x00000000005c481e in _D3dmd9dtemplate15functionResolveFPSQBi11declaration5MatchCQCf7dsymbol7DsymbolSQCz7globals3LocPSQDq6dscope5ScopePSQEi4root5array__T5ArrayTCQFhQz10rootobject10RootObjectZQBmCQGp5mtype4TypePSQHfQCxQCv__TQCsTCQHw10expression10ExpressionZQDzPPxaZ10__lambda11MFQHqZi ( __capture=0x7fffffff9a00, s=0x7ffff6d46370) at dmd/dtemplate.d:2814 #5 0x000000000060e20c in _D3dmd4func13overloadApplyFCQBa7dsymbol7DsymbolMDFQxZiPSQCc6dscope5ScopeZi (sc=0x7ffff6aa55f0, dg=..., fstart=0x7ffff6d45e00) at dmd/func.d:2566 ---Type <return> to continue, or q <return> to quit--- #6 0x00000000005c3149 in _D3dmd9dtemplate15functionResolveFPSQBi11declaration5MatchCQCf7dsymbol7DsymbolSQCz7globals3LocPSQDq6dscope5ScopePSQEi4root5array__T5ArrayTCQFhQz10rootobject10RootObjectZQBmCQGp5mtype4TypePSQHfQCxQCv__TQCsTCQHw10expression10ExpressionZQDzPPxaZv (pMessage=0x0, fargs=0x7ffff6aa4b70, tthis=0x7ffff6d46860, tiargs=0x0, sc=0x7ffff6aa55f0, loc=..., dstart=0x7ffff6d45e00, m=0x7fffffff9a48) at dmd/dtemplate.d:2818 #7 0x000000000060e522 in _D3dmd4func15resolveFuncCallFKxSQBe7globals3LocPSQBv6dscope5ScopeCQCm7dsymbol7DsymbolPSQDh4root5array__T5ArrayTCQEgQz10rootobject10RootObjectZQBmCQFo5mtype4TypePSQGeQCxQCv__TQCsTCQGv10expression10ExpressionZQDzEQIbQIa15FuncResolveFlagZCQJaQIz15FuncDeclaration ( flags=0 '\000', fargs=0x7ffff6aa4b70, tthis=0x7ffff6d46860, tiargs=0x0, s=0x7ffff6d45e00, sc=0x7ffff6aa55f0, loc=...) at dmd/func.d:2721 #8 0x00000000005f1eba in ExpressionSemanticVisitor::visit(CallExp*) (this=0x7fffffffa4b8, exp=0x7ffff6aa5950) at dmd/expressionsem.d:4327 #9 0x00000000005e0656 in CallExp::accept(Visitor*) (this=0x7ffff6aa5950, v=0x7fffffffa4b8) at dmd/expression.d:4892 #10 0x0000000000606333 in expressionSemantic(Expression*, Scope*) (e=0x7ffff6aa5950, sc=0x7ffff6aa55f0) at dmd/expressionsem.d:10777 ---Type <return> to continue, or q <return> to quit--- #11 0x00000000005f1972 in ExpressionSemanticVisitor::visit(CallExp*) (this=0x7fffffffac48, exp=0x7ffff6aa4b20) at dmd/expressionsem.d:4193 #12 0x00000000005e0656 in CallExp::accept(Visitor*) (this=0x7ffff6aa4b20, v=0x7fffffffac48) at dmd/expression.d:4892 #13 0x0000000000606333 in expressionSemantic(Expression*, Scope*) (e=0x7ffff6aa4b20, sc=0x7ffff6aa55f0) at dmd/expressionsem.d:10777 #14 0x00000000006a1cce in StatementSemanticVisitor::visit(ExpStatement*) (this=0x7fffffffad18, s=0x7ffff6aa4b00) at dmd/statementsem.d:176 #15 0x00000000006812ae in ExpStatement::accept(Visitor*) (this=0x7ffff6aa4b00, v=0x7fffffffad18) at dmd/statement.d:738 #16 0x00000000006a1bb7 in statementSemantic(Statement*, Scope*) (s=0x7ffff6aa4b00, sc=0x7ffff6aa55f0) at dmd/statementsem.d:125 #17 0x00000000006a1f90 in StatementSemanticVisitor::visit(CompoundStatement*) ( this=0x7fffffffb048, cs=0x7ffff6aa4ac0) at dmd/statementsem.d:234 #18 0x0000000000681b0e in CompoundStatement::accept(Visitor*) (this=0x7ffff6aa4ac0, v=0x7fffffffb048) at dmd/statement.d:935 ---Type <return> to continue, or q <return> to quit--- #19 0x00000000006a1bb7 in statementSemantic(Statement*, Scope*) (s=0x7ffff6aa4ac0, sc=0x7ffff6aa55f0) at dmd/statementsem.d:125 #20 0x00000000006b6e9e in Semantic3Visitor::visit(FuncDeclaration*) (this=0x7fffffffbba0, funcdecl=0x7ffff6aa4680) at dmd/semantic3.d:573 #21 0x00000000006b9c1f in Semantic3Visitor::visit(CtorDeclaration*) (this=0x7fffffffbba0, ctor=0x7ffff6aa4680) at dmd/semantic3.d:1318 #22 0x000000000060fdf2 in CtorDeclaration::accept(Visitor*) (this=0x7ffff6aa4680, v=0x7fffffffbba0) at dmd/func.d:3373 #23 0x00000000006b57b5 in semantic3(Dsymbol*, Scope*) (dsym=0x7ffff6aa4680, sc=0x7ffff6aa3ed0) at dmd/semantic3.d:82 #24 0x0000000000609482 in FuncDeclaration::functionSemantic3() (this=0x7ffff6aa4680) at dmd/func.d:420 #25 0x0000000000609398 in FuncDeclaration::functionSemantic() (this=0x7ffff6aa4680) at dmd/func.d:394 #26 0x000000000060e568 in _D3dmd4func15resolveFuncCallFKxSQBe7globals3LocPSQBv6dscope5ScopeCQCm7dsymbol7DsymbolPSQDh4root5array__T5ArrayTCQEgQz10rootobject10RootObjectZQBmCQFo5mtype4TypePSQGeQCxQCv__T---Type <return> to continue, or q <return> to quit--- QCsTCQGv10expression10ExpressionZQDzEQIbQIa15FuncResolveFlagZCQJaQIz15FuncDeclaration ( flags=0 '\000', fargs=0x7ffff6aa32d0, tthis=0x7ffff6d45b60, tiargs=0x0, s=0x7ffff6d45800, sc=0x7ffff6aa3070, loc=...) at dmd/func.d:2729 #27 0x00000000005f1eba in ExpressionSemanticVisitor::visit(CallExp*) (this=0x7fffffffc6c8, exp=0x7ffff6aa3280) at dmd/expressionsem.d:4327 #28 0x00000000005e0656 in CallExp::accept(Visitor*) (this=0x7ffff6aa3280, v=0x7fffffffc6c8) at dmd/expression.d:4892 #29 0x0000000000606333 in expressionSemantic(Expression*, Scope*) (e=0x7ffff6aa3280, sc=0x7ffff6aa3070) at dmd/expressionsem.d:10777 #30 0x0000000000625005 in _D3dmd7initsem19initializerSemanticRCQBj4init11InitializerPSQCg6dscope5ScopeCQCx5mtype4TypeEQDmQCd13NeedInterpretZ8visitExpMFCQEuQDl14ExpInitializerZQEj ( __capture=0x7fffffffc850, i=0x7ffff6aa3180) at dmd/initsem.d:457 #31 0x0000000000623483 in initializerSemantic(Initializer*, Scope*, Type*, NeedInterpret) ( init=0x7ffff6aa3180, sc=0x7ffff6aa3070, t=0x7ffff6d45b60, needInterpret=<incomplete type>) at dmd/initsem.d:523 #32 0x000000000068b06e in _D3dmd7typesem12typeSemanticRCQBc5mtype4TypeSQBr7globals3LocPSQCi6dscope5S---Type <return> to continue, or q <return> to quit--- copeZ13visitFunctionMFCQDrQCp12TypeFunctionZQDl (__capture=0x7fffffffcb70, mtype=0x7ffff6d462b0) at dmd/typesem.d:1353 #33 0x0000000000688bea in typeSemantic(Type*, Loc, Scope*) (t=0x7ffff6d462b0, loc=..., sc=0x7ffff6aa2d70) at dmd/typesem.d:1814 #34 0x00000000005b4bd7 in DsymbolSemanticVisitor::funcDeclarationSemantic(FuncDeclaration*) ( this=0x7fffffffd240, funcdecl=0x7ffff6d46370) at dmd/dsymbolsem.d:3093 #35 0x00000000005b6b24 in DsymbolSemanticVisitor::visit(CtorDeclaration*) (this=0x7fffffffd240, ctd=0x7ffff6d46370) at dmd/dsymbolsem.d:3735 #36 0x000000000060fdf2 in CtorDeclaration::accept(Visitor*) (this=0x7ffff6d46370, v=0x7fffffffd240) at dmd/func.d:3373 #37 0x00000000005ac291 in dsymbolSemantic(Dsymbol*, Scope*) (dsym=0x7ffff6d46370, sc=0x7ffff6aa2680) at dmd/dsymbolsem.d:365 #38 0x00000000005b8f34 in _D3dmd10dsymbolsem22DsymbolSemanticVisitor5visitMRCQBx7dstruct17StructDeclarationZ__T9__lambda5TCQDr7dsymbol7DsymbolZQBgMFQBaZv (__capture=0x7fffffffd440, s=0x7ffff6d46370) at dmd/dsymbolsem.d:4295 #39 0x00000000005a66bc in _D3dmd7dsymbol14foreachDsymbolFPSQBf4root5array__T5ArrayTCQCeQCd7DsymbolZQ---Type <return> to continue, or q <return> to quit--- xMDFQvZvZv (dg=..., symbols=0x7ffff6d45c10) at dmd/dsymbol.d:97 #40 0x00000000005b88a6 in DsymbolSemanticVisitor::visit(StructDeclaration*) (this=0x7fffffffd490, sd=0x7ffff6d46620) at dmd/dsymbolsem.d:4295 #41 0x00000000005a6142 in StructDeclaration::accept(Visitor*) (this=0x7ffff6d46620, v=0x7fffffffd490) at dmd/dstruct.d:592 #42 0x00000000005ac291 in dsymbolSemantic(Dsymbol*, Scope*) (dsym=0x7ffff6d46620, sc=0x7ffff6d46af0) at dmd/dsymbolsem.d:365 #43 0x00000000005b16a8 in _D3dmd10dsymbolsem22DsymbolSemanticVisitor5visitMRCQBx7dmodule6ModuleZ__T9__lambda2TCQDf7dsymbol7DsymbolZQBgMFQBaZv (__capture=0x7fffffffd540, s=0x7ffff6d46620) at dmd/dsymbolsem.d:1979 #44 0x00000000005a66bc in _D3dmd7dsymbol14foreachDsymbolFPSQBf4root5array__T5ArrayTCQCeQCd7DsymbolZQxMDFQvZvZv (dg=..., symbols=0x7ffff6d45030) at dmd/dsymbol.d:97 #45 0x00000000005b1634 in DsymbolSemanticVisitor::visit(Module*) (this=0x7fffffffd590, m=0x7ffff6d44d80) at dmd/dsymbolsem.d:1976 #46 0x0000000000594d7a in Module::accept(Visitor*) (this=0x7ffff6d44d80, v=0x7fffffffd590) at dmd/dmodule.d:1290 ---Type <return> to continue, or q <return> to quit--- #47 0x00000000005ac291 in dsymbolSemantic(Dsymbol*, Scope*) (dsym=0x7ffff6d44d80, sc=0x0) at dmd/dsymbolsem.d:365 #48 0x0000000000649553 in _D3dmd4mars7tryMainFmPPxaKSQz7globals5ParamZi (params=..., argv=0x7fffffffdf98, argc=2) at dmd/mars.d:560 #49 0x000000000064aaf5 in D main () at dmd/mars.d:859 Maybe it's possible at some point to launch the semantic of the other thing when the scope is null probably at step #3 or #4

reduced : module b19691; struct S1 { this(T)(T) { S2(""); } } struct S2 { this(S1 s = ""){} }

The reduction is actually slightly different. With the upcoming fix the initial test case will pass an fall back on the string overload (even if with a dep message) but the reduction will fail.

@Basile-z created dlang/dmd pull request #9397 "fix issue 19691 - ICE on null default value for struct parameter in constructor" fixing this issue: - fix issue 19691 - ICE on null default value for struct parameter in constructor https://github.com/dlang/dmd/pull/9397

dlang/dmd pull request #9397 "fix issue 19691 - ICE on null default value for struct parameter in constructor" was merged into master: - 81b0ed15918bfc3608b28e443121fa7bc982f5d8 by Basile Burg: fix issue 19691 - ICE on null default value for struct parameter in constructor https://github.com/dlang/dmd/pull/9397

dlang/dmd pull request #10046 "[dmd-cxx] Backport semanticRun refactoring and recursive semantic SEGV bug fixes" was merged into dmd-cxx: - b90e1fdd85d62c535f22944540ab7ca525d57bb2 by Basile Burg: fix issue 19691 - ICE on null default value for struct parameter in constructor https://github.com/dlang/dmd/pull/10046