fix Issue 17784 - [scope][DIP1000] Confusing error message for escapi… #8054
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Thanks for your pull request, @WalterBright! Bugzilla references
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WalterBright
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| if (global.params.vsafe) // https://issues.dlang.org/show_bug.cgi?id=17029 | ||
| { | ||
| if (!gag) | ||
| error(e.loc, "scope variable `%s` may not be copied into allocated memory", v.toChars()); |
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I suggest using the term "GC-allocated memory" to be more precise. The problem isn't about memory (per se) or its allocation but about the lifetimes of objects under the jurisdiction of the GC. I suggest something like:
scope variable
%smay not be copied into GC-allocated memory because doing so would cause it to escape
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I didn't use that term because the message could apply to any allocated memory.
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We run the risk of turning D into Rust, where instead of users fighting the borrow checker, they'll be fighting the scope checker. The wording of the error messages will become increasingly important to help users understand precisely what the problem is. |
| if (tb.ty == Tarray || tb.ty == Tsarray) | ||
| { | ||
| if (!gag) | ||
| error(e.loc, "copying `%s` into allocated memory escapes a reference to variadic parameter `%s`", e.toChars(), v.toChars()); |
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My suggestion:
copying
%sinto GC-allocated memory escapes a reference to variadic parameter%s
| if (!gag) | ||
| { | ||
| const(char)* kind = (v.storage_class & STC.parameter) ? "parameter" : "local"; | ||
| error(e.loc, "copying `%s` into allocated memory escapes a reference to %s variable `%s`", |
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I suggest:
copying
%sinto GC-allocated memory escapes a reference to %s variable%s
src/dmd/escape.d
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| if (tf.isref) | ||
| { | ||
| if (!gag) | ||
| error(e.loc, "storing reference to outer local variable `%s` into allocated memory", v.toChars()); |
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Not sure I understand what the intention is, but if my understanding is correct I suggest:
storing a reference to outer local variable
%sinto GC-allocated memory causes it to escape
src/dmd/escape.d
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| { | ||
| if (log) printf("byexp %s\n", ee.toChars()); | ||
| if (!gag) | ||
| error(ee.loc, "storing reference to stack allocated value returned by `%s` into allocated memory", |
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I suggest:
storing a reference to a stack allocated value returned by
%sinto GC-allocated memory causes it to escape
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In principle I agree with @JinShil, but I think that the source of the momery allocation (e.g. GC vs malloc vs static) doesn't matter, so it's better to simply say "storing / copying [..] to an object with greater lifetime". |
…ng local via new-expression
I tend to think of lifetimes in relationship to lexical scopes, so I prefer using "allocated memory" instead. |
…ng local via new-expression
This splits off
checkNewEscape()fromcheckReturnEscapeImpl()which enables customizing the error messages and removes confusing logic trying to deal with both Return and New.