Bug 21229 – [REG 2.080.2] Constructor flow analysis doesn't understand unions

Example program: --- struct NeedsInit { int n; @disable this(); } union U { NeedsInit a; } struct S { U u; this(NeedsInit arg){ u.a = arg; } } --- Compiler output, from run.dlang.io: Up to 2.060 : Failure with output: ----- onlineapp.d(15): Error: can only initialize const member a inside constructor onlineapp.d(15): Error: can only initialize const member a inside constructor onlineapp.d(15): Error: constructor onlineapp.S.this field u must be initialized in constructor ----- 2.061 to 2.080.1: Success and no output Since 2.081.2: Failure with output: onlineapp.d(15): Error: field `u` must be initialized in constructor This appears to be a known bug, since there is a comment about unions in `dmd.semantic3.Semantic3Visitor.visit(FuncDeclaration)`: /* Current bugs in the flow analysis: * 1. union members should not produce error messages even if * not assigned to * 2. structs should recognize delegating opAssign calls as well * as delegating calls to other constructors */

@MoonlightSentinel updated dlang/dmd pull request #12402 "Fix 21229 - Accept construction of union member as initialization" fixing this issue: - Fix 21229 - Accept construction of a unions member as initialization Because the `union` is initialised when one of its members has been constructed. https://github.com/dlang/dmd/pull/12402

dlang/dmd pull request #12402 "Fix 21229 - Accept construction of union member as initialization" was merged into stable: - d123fabb47d7c64a25997b8d2dcc2f1a7e981469 by MoonlightSentinel: Fix 21229 - Accept construction of a unions member as initialization Because the `union` is initialised when one of its members has been constructed. https://github.com/dlang/dmd/pull/12402

dlang/dmd pull request #12408 "Merge stable into master" was merged into master: - 655278312e2851b74b1f88dd71c7ffdb47224c20 by MoonlightSentinel: Fix 21229 - Accept construction of a unions member as initialization Because the `union` is initialised when one of its members has been constructed. https://github.com/dlang/dmd/pull/12408