Fix __traits(getMember, this, ...) not capturing enclosing this in nested functions - #23437
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Fix __traits(getMember, this, ...) not capturing enclosing this in nested functions#23437niy-ati wants to merge 1 commit into
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…sted functions getMember with wantsym returns the member VarDeclaration without a ThisExp use, so nested functions that only access a field through getMember(this, ...) never register a nested reference to the enclosing this and the compiler omits vthis from the closure frame. After expressionSemantic on the resolved member, when the lookup object is this, call checkNestedReference on te.var so closure building matches a direct field access. Fixes dlang#23436.
dkorpel
requested changes
Jul 20, 2026
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| // getMember with wantsym returns the member VarDeclaration | ||
| // without a ThisExp use, so nested functions that only access | ||
| // a field through getMember(this, ...) never register a nested | ||
| // reference to the enclosing `this`. Force that here. | ||
| if (ex && !ex.isErrorExp()) | ||
| { | ||
| if (auto e0 = isExpression(o)) | ||
| { | ||
| e0 = e0.expressionSemantic(sc); | ||
| if (auto te = e0.isThisExp()) | ||
| { | ||
| if (te.var && te.var.checkNestedReference(sc, e.loc)) | ||
| return ErrorExp.get(); | ||
| } | ||
| } | ||
| } |
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This kind of "if (code == issue) fix();" patch is not robust
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Summary
__traits(getMember, this, "field")inside a nested function does not register a nested reference to the enclosing memberthis. The compiler then omitsvthisfrom the closure frame, causing a segfault when the delegate runs.getMemberwithwantsymreturns the memberVarDeclarationwithout keeping aThisExpuse. AfterexpressionSemanticon the resolved member, when the lookup object isthis, this patch callscheckNestedReferenceonte.varso closure building matches a direct field access.Test plan
Added
compiler/test/runnable/test_getMember_nested_this.d: nested function returned as a delegate that reads a field viagetMemberonthis.Fixes #23436.
Also fixes ldc-developers/ldc#5203.