From fe528829866f08bac8cf6615085ec4609db352e9 Mon Sep 17 00:00:00 2001 From: Ezra Shaw Date: Fri, 16 Dec 2022 18:24:14 +1300 Subject: [PATCH] docs: add long error explanation for error E0320 --- compiler/rustc_error_codes/src/error_codes.rs | 2 +- .../src/error_codes/E0320.md | 27 +++++++++++++++++++ .../dropck_no_diverge_on_nonregular_1.stderr | 1 + .../dropck_no_diverge_on_nonregular_2.stderr | 1 + .../dropck_no_diverge_on_nonregular_3.stderr | 1 + ...-38591-non-regular-dropck-recursion.stderr | 1 + 6 files changed, 32 insertions(+), 1 deletion(-) create mode 100644 compiler/rustc_error_codes/src/error_codes/E0320.md diff --git a/compiler/rustc_error_codes/src/error_codes.rs b/compiler/rustc_error_codes/src/error_codes.rs index 31a709c36d4..67c512e98d6 100644 --- a/compiler/rustc_error_codes/src/error_codes.rs +++ b/compiler/rustc_error_codes/src/error_codes.rs @@ -163,6 +163,7 @@ E0311: include_str!("./error_codes/E0311.md"), E0312: include_str!("./error_codes/E0312.md"), E0316: include_str!("./error_codes/E0316.md"), E0317: include_str!("./error_codes/E0317.md"), +E0320: include_str!("./error_codes/E0320.md"), E0321: include_str!("./error_codes/E0321.md"), E0322: include_str!("./error_codes/E0322.md"), E0323: include_str!("./error_codes/E0323.md"), @@ -575,7 +576,6 @@ E0791: include_str!("./error_codes/E0791.md"), // E0314, // closure outlives stack frame // E0315, // cannot invoke closure outside of its lifetime // E0319, // trait impls for defaulted traits allowed just for structs/enums - E0320, // recursive overflow during dropck // E0372, // coherence not object safe E0377, // the trait `CoerceUnsized` may only be implemented for a coercion // between structures with the same definition diff --git a/compiler/rustc_error_codes/src/error_codes/E0320.md b/compiler/rustc_error_codes/src/error_codes/E0320.md new file mode 100644 index 00000000000..e6e1b7c19a5 --- /dev/null +++ b/compiler/rustc_error_codes/src/error_codes/E0320.md @@ -0,0 +1,27 @@ +Recursion limit reached while creating drop-check rules. + +Example of erroneous code: + +```compile_fail,E0320 +enum A { + B, + C(T, Box>) +} + +fn foo() { + A::::B; // error: overflow while adding drop-check rules for A +} +``` + +The Rust compiler must be able to reason about how a type is [`Drop`]ped, and +by extension the types of its fields, to be able to generate the glue to +properly drop a value. The code example above shows a type where this inference +is impossible because it is recursive. Note that this is *not* the same as +[E0072](E0072.html), where a type has an infinite size; the type here has a +finite size but any attempt to `Drop` it would recurse infinitely. For more +information, read [the `Drop` docs](../std/ops/trait.Drop.html). + +It is not possible to define a type with recursive drop-check rules. All such +recursion must be removed. + +[`Drop`]: ../std/ops/trait.Drop.html diff --git a/src/test/ui/dropck/dropck_no_diverge_on_nonregular_1.stderr b/src/test/ui/dropck/dropck_no_diverge_on_nonregular_1.stderr index c447e2f7987..3e39d15f9b0 100644 --- a/src/test/ui/dropck/dropck_no_diverge_on_nonregular_1.stderr +++ b/src/test/ui/dropck/dropck_no_diverge_on_nonregular_1.stderr @@ -8,3 +8,4 @@ LL | let ft = error: aborting due to previous error +For more information about this error, try `rustc --explain E0320`. diff --git a/src/test/ui/dropck/dropck_no_diverge_on_nonregular_2.stderr b/src/test/ui/dropck/dropck_no_diverge_on_nonregular_2.stderr index cd4706dd903..dbb74354471 100644 --- a/src/test/ui/dropck/dropck_no_diverge_on_nonregular_2.stderr +++ b/src/test/ui/dropck/dropck_no_diverge_on_nonregular_2.stderr @@ -8,3 +8,4 @@ LL | let ft = error: aborting due to previous error +For more information about this error, try `rustc --explain E0320`. diff --git a/src/test/ui/dropck/dropck_no_diverge_on_nonregular_3.stderr b/src/test/ui/dropck/dropck_no_diverge_on_nonregular_3.stderr index 18cd1b6cd41..deaf116b647 100644 --- a/src/test/ui/dropck/dropck_no_diverge_on_nonregular_3.stderr +++ b/src/test/ui/dropck/dropck_no_diverge_on_nonregular_3.stderr @@ -16,3 +16,4 @@ LL | Some(Wrapper::Simple::); error: aborting due to 2 previous errors +For more information about this error, try `rustc --explain E0320`. diff --git a/src/test/ui/recursion/issue-38591-non-regular-dropck-recursion.stderr b/src/test/ui/recursion/issue-38591-non-regular-dropck-recursion.stderr index 1da29be43db..002dfe115b0 100644 --- a/src/test/ui/recursion/issue-38591-non-regular-dropck-recursion.stderr +++ b/src/test/ui/recursion/issue-38591-non-regular-dropck-recursion.stderr @@ -8,3 +8,4 @@ LL | fn f(x: S) {} error: aborting due to previous error +For more information about this error, try `rustc --explain E0320`.