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bors d4d129d566 Auto merge of #85012 - FabianWolff:struct-rec, r=davidtwco 
Fix stack overflow when checking for structural recursion

This pull request aims to fix #74224 and fix #84611. The current logic for detecting ADTs with structural recursion is flawed because it only looks at the root type, and then for exact matches. What I mean by this is that for examples such as:
```rust
struct A<T> {
    x: T,
    y: A<A<T>>,
}

struct B {
    z: A<usize>
}

fn main() {}
```
When checking `A`, the compiler correctly determines that it has an infinite size (because the "root" type is `A`, and `A` occurs, albeit with different type arguments, as a nested type in `A`).

However, when checking `B`, it also recurses into `A`, but now `B` is the root type, and it only checks for _exact_ matches of `A`, but since `A` never precisely contains itself (only `A<A<T>>`, `A<A<A<T>>>`, etc.), an endless recursion ensues until the stack overflows.

In this PR, I have attempted to fix this behavior by implementing a two-phase checking: When checking `B`, my code first checks `A` _separately_ and stops if `A` already turns out to be infinite. If not (such as for `Option<T>`), the second phase checks whether the root type (`B`) is ever nested inside itself, e.g.:
```rust
struct Foo { x: Option<Option<Foo>> }
```

Special care needs to be taken for mutually recursive types, e.g.:
```rust
struct A<T> {
    z: T,
    x: B<T>,
}

struct B<T> {
    y: A<T>
}
```
Here, both `A` and `B` both _are_ `SelfRecursive` and _contain_ a recursive type. The current behavior, which I have maintained, is to treat both `A` and `B` as `SelfRecursive`, and accordingly report errors for both.
2021-05-11 00:00:53 +00:00
..
auxiliary tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
struct-rec Implement changes suggested by tmiasko and davidtwco 2021-05-10 17:47:50 +02:00
align-enum.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
align-struct.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
borrow-tuple-fields.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
class-cast-to-trait-cross-crate-2.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
class-cast-to-trait-multiple-types.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
class-cast-to-trait.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
class-dtor.rs Update code to account for extern ABI requirement 2021-01-13 07:49:45 -05:00
class-exports.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
class-impl-very-parameterized-trait.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
class-implement-trait-cross-crate.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
class-implement-traits.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
class-method-cross-crate.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
class-methods-cross-crate.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
class-methods.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
class-poly-methods-cross-crate.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
class-poly-methods.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
class-separate-impl.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
class-str-field.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
class-typarams.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
classes-cross-crate.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
classes-self-referential.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
classes-simple-cross-crate.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
classes-simple-method.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
classes-simple.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
classes.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
codegen-tag-static-padding.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
compare-generic-enums.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
discrim-explicit-23030.rs Remove compile-fail test suite 2020-12-29 23:39:56 +03:00
empty-struct-braces.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
empty-tag.rs update tests 2020-03-31 19:01:49 +02:00
enum-alignment.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
enum-clike-ffi-as-int.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
enum-discr.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
enum-discrim-autosizing.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
enum-discrim-manual-sizing.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
enum-discrim-range-overflow.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
enum-discrim-width-stuff.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
enum-disr-val-pretty.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
enum-export-inheritance.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
enum-layout-optimization.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
enum-non-c-like-repr-c-and-int.rs Remove mem::uninitalized from tests 2019-12-22 21:58:12 -05:00
enum-non-c-like-repr-c.rs Remove mem::uninitalized from tests 2019-12-22 21:58:12 -05:00
enum-non-c-like-repr-int.rs Remove mem::uninitalized from tests 2019-12-22 21:58:12 -05:00
enum-null-pointer-opt.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
enum-nullable-const-null-with-fields.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
enum-nullable-simplifycfg-misopt.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
enum-univariant-repr.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
enum-variants.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
enum-vec-initializer.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
export-abstract-tag.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
export-tag-variant.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
expr-if-struct.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
expr-match-struct.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
field-destruction-order.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
foreign-struct.rs Update tests for extern block linting 2021-01-13 07:49:16 -05:00
functional-struct-upd.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
issue-1701.rs Move some tests to more reasonable directories - 5 2021-03-20 11:41:24 -03:00
ivec-tag.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
module-qualified-struct-destructure.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
namespaced-enum-emulate-flat-xc.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
namespaced-enum-emulate-flat.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
namespaced-enum-glob-import-xcrate.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
namespaced-enum-glob-import.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
namespaced-enums-xcrate.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
namespaced-enums.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
nested-enum-same-names.rs Fix new 'unnecessary trailing semicolon' warnings 2020-11-26 17:08:36 -05:00
newtype-struct-drop-run.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
newtype-struct-with-dtor.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
newtype-struct-xc-2.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
newtype-struct-xc.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
nonzero-enum.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
numeric-fields.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
object-lifetime-default-from-ref-struct.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
object-lifetime-default-from-rptr-struct.rs Remove compile-fail test suite 2020-12-29 23:39:56 +03:00
rec-align-u32.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
rec-align-u64.rs Fix up/ignore failing ui tests on fuchsia 2021-05-06 02:49:34 +00:00
rec-auto.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
rec-extend.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
rec-tup.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
rec.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
record-pat.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
resource-in-struct.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
simple-generic-tag.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
simple-match-generic-tag.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
small-enum-range-edge.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
small-enums-with-fields.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
struct-aliases-xcrate.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
struct-aliases.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
struct-destructuring-cross-crate.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
struct-field-shorthand.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
struct-like-variant-construct.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
struct-like-variant-match.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
struct-lit-functional-no-fields.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
struct-literal-dtor.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
struct-new-as-field-name.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
struct-order-of-eval-1.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
struct-order-of-eval-2.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
struct-order-of-eval-3.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
struct-order-of-eval-4.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
struct-partial-move-1.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
struct-partial-move-2.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
struct-path-associated-type.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
struct-path-self.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
struct-pattern-matching.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
struct-variant-field-visibility.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
struct_variant_xc.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
struct_variant_xc_match.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
tag-align-dyn-u64.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
tag-align-dyn-variants.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
tag-align-shape.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
tag-align-u64.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
tag-disr-val-shape.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
tag-exports.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
tag-in-block.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
tag-variant-disr-type-mismatch.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
tag-variant-disr-val.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
tag.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
tuple-struct-construct.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
tuple-struct-constructor-pointer.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
tuple-struct-destructuring.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
tuple-struct-matching.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
tuple-struct-trivial.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
type-sizes.rs Move some tests to more reasonable directories 2021-02-16 21:22:21 -03:00
uninstantiable-struct.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
unit-like-struct-drop-run.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
unit-like-struct.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00
variant-structs-trivial.rs tests: Move run-pass tests without naming conflicts to ui 2019-07-27 18:56:16 +03:00