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inline_const
blocks type inference
#89964
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C-bug
Category: This is a bug.
F-inline_const
Inline constants (aka: const blocks, const expressions, anonymous constants)
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scottmcm
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C-bug
Category: This is a bug.
F-inline_const
Inline constants (aka: const blocks, const expressions, anonymous constants)
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Oct 16, 2021
cc @lcnr |
this is a known issue and fixed by #89561 |
matthiaskrgr
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Nov 8, 2021
Type inference for inline consts Fixes rust-lang#78132 Fixes rust-lang#78174 Fixes rust-lang#81857 Fixes rust-lang#89964 Perform type checking/inference of inline consts in the same context as the outer def, similar to what is currently done to closure. Doing so would require `closure_base_def_id` of the inline const to return the outer def, and since `closure_base_def_id` can be called on non-local crate (and thus have no HIR available), a new `DefKind` is created for inline consts. The type of the generated anon const can capture lifetime of outer def, so we couldn't just use the typeck result as the type of the inline const's def. Closure has a similar issue, and it uses extra type params `CK, CS, U` to capture closure kind, input/output signature and upvars. I use a similar approach for inline consts, letting it have an extra type param `R`, and then `typeof(InlineConst<[paremt generics], R>)` would just be `R`. In borrowck region requirements are also propagated to the outer MIR body just like it's currently done for closure. With this PR, inline consts in expression position are quitely usable now; however the usage in pattern position is still incomplete -- since those does not remain in the MIR borrowck couldn't verify the lifetime there. I have left an ignored test as a FIXME. Some disucssions can be found on [this Zulip thread](https://rust-lang.zulipchat.com/#narrow/stream/260443-project-const-generics/topic/inline.20consts.20typeck). cc `@spastorino` `@lcnr` r? `@nikomatsakis` `@rustbot` label A-inference F-inline_const T-compiler
matthiaskrgr
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Nov 8, 2021
Type inference for inline consts Fixes rust-lang#78132 Fixes rust-lang#78174 Fixes rust-lang#81857 Fixes rust-lang#89964 Perform type checking/inference of inline consts in the same context as the outer def, similar to what is currently done to closure. Doing so would require `closure_base_def_id` of the inline const to return the outer def, and since `closure_base_def_id` can be called on non-local crate (and thus have no HIR available), a new `DefKind` is created for inline consts. The type of the generated anon const can capture lifetime of outer def, so we couldn't just use the typeck result as the type of the inline const's def. Closure has a similar issue, and it uses extra type params `CK, CS, U` to capture closure kind, input/output signature and upvars. I use a similar approach for inline consts, letting it have an extra type param `R`, and then `typeof(InlineConst<[paremt generics], R>)` would just be `R`. In borrowck region requirements are also propagated to the outer MIR body just like it's currently done for closure. With this PR, inline consts in expression position are quitely usable now; however the usage in pattern position is still incomplete -- since those does not remain in the MIR borrowck couldn't verify the lifetime there. I have left an ignored test as a FIXME. Some disucssions can be found on [this Zulip thread](https://rust-lang.zulipchat.com/#narrow/stream/260443-project-const-generics/topic/inline.20consts.20typeck). cc ``@spastorino`` ``@lcnr`` r? ``@nikomatsakis`` ``@rustbot`` label A-inference F-inline_const T-compiler
matthiaskrgr
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Nov 8, 2021
Type inference for inline consts Fixes rust-lang#78132 Fixes rust-lang#78174 Fixes rust-lang#81857 Fixes rust-lang#89964 Perform type checking/inference of inline consts in the same context as the outer def, similar to what is currently done to closure. Doing so would require `closure_base_def_id` of the inline const to return the outer def, and since `closure_base_def_id` can be called on non-local crate (and thus have no HIR available), a new `DefKind` is created for inline consts. The type of the generated anon const can capture lifetime of outer def, so we couldn't just use the typeck result as the type of the inline const's def. Closure has a similar issue, and it uses extra type params `CK, CS, U` to capture closure kind, input/output signature and upvars. I use a similar approach for inline consts, letting it have an extra type param `R`, and then `typeof(InlineConst<[paremt generics], R>)` would just be `R`. In borrowck region requirements are also propagated to the outer MIR body just like it's currently done for closure. With this PR, inline consts in expression position are quitely usable now; however the usage in pattern position is still incomplete -- since those does not remain in the MIR borrowck couldn't verify the lifetime there. I have left an ignored test as a FIXME. Some disucssions can be found on [this Zulip thread](https://rust-lang.zulipchat.com/#narrow/stream/260443-project-const-generics/topic/inline.20consts.20typeck). cc ```@spastorino``` ```@lcnr``` r? ```@nikomatsakis``` ```@rustbot``` label A-inference F-inline_const T-compiler
matthiaskrgr
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Nov 8, 2021
Type inference for inline consts Fixes rust-lang#78132 Fixes rust-lang#78174 Fixes rust-lang#81857 Fixes rust-lang#89964 Perform type checking/inference of inline consts in the same context as the outer def, similar to what is currently done to closure. Doing so would require `closure_base_def_id` of the inline const to return the outer def, and since `closure_base_def_id` can be called on non-local crate (and thus have no HIR available), a new `DefKind` is created for inline consts. The type of the generated anon const can capture lifetime of outer def, so we couldn't just use the typeck result as the type of the inline const's def. Closure has a similar issue, and it uses extra type params `CK, CS, U` to capture closure kind, input/output signature and upvars. I use a similar approach for inline consts, letting it have an extra type param `R`, and then `typeof(InlineConst<[paremt generics], R>)` would just be `R`. In borrowck region requirements are also propagated to the outer MIR body just like it's currently done for closure. With this PR, inline consts in expression position are quitely usable now; however the usage in pattern position is still incomplete -- since those does not remain in the MIR borrowck couldn't verify the lifetime there. I have left an ignored test as a FIXME. Some disucssions can be found on [this Zulip thread](https://rust-lang.zulipchat.com/#narrow/stream/260443-project-const-generics/topic/inline.20consts.20typeck). cc ````@spastorino```` ````@lcnr```` r? ````@nikomatsakis```` ````@rustbot```` label A-inference F-inline_const T-compiler
flip1995
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Nov 23, 2021
Type inference for inline consts Fixes rust-lang#78132 Fixes rust-lang#78174 Fixes rust-lang#81857 Fixes rust-lang#89964 Perform type checking/inference of inline consts in the same context as the outer def, similar to what is currently done to closure. Doing so would require `closure_base_def_id` of the inline const to return the outer def, and since `closure_base_def_id` can be called on non-local crate (and thus have no HIR available), a new `DefKind` is created for inline consts. The type of the generated anon const can capture lifetime of outer def, so we couldn't just use the typeck result as the type of the inline const's def. Closure has a similar issue, and it uses extra type params `CK, CS, U` to capture closure kind, input/output signature and upvars. I use a similar approach for inline consts, letting it have an extra type param `R`, and then `typeof(InlineConst<[paremt generics], R>)` would just be `R`. In borrowck region requirements are also propagated to the outer MIR body just like it's currently done for closure. With this PR, inline consts in expression position are quitely usable now; however the usage in pattern position is still incomplete -- since those does not remain in the MIR borrowck couldn't verify the lifetime there. I have left an ignored test as a FIXME. Some disucssions can be found on [this Zulip thread](https://rust-lang.zulipchat.com/#narrow/stream/260443-project-const-generics/topic/inline.20consts.20typeck). cc `````@spastorino````` `````@lcnr````` r? `````@nikomatsakis````` `````@rustbot````` label A-inference F-inline_const T-compiler
GuillaumeGomez
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Apr 22, 2024
Stabilise inline_const # Stabilisation Report ## Summary This PR will stabilise `inline_const` feature in expression position. `inline_const_pat` is still unstable and will *not* be stabilised. The feature will allow code like this: ```rust foo(const { 1 + 1 }) ``` which is roughly desugared into ```rust struct Foo; impl Foo { const FOO: i32 = 1 + 1; } foo(Foo::FOO) ``` This feature is from rust-lang/rfcs#2920 and is tracked in rust-lang#76001 (the tracking issue should *not* be closed as it needs to track inline const in pattern position). The initial implementation is done in rust-lang#77124. ## Difference from RFC There are two major differences (enhancements) as implemented from the RFC. First thing is that the RFC says that the type of an inline const block inferred from the content *within* it, but we currently can infer the type using the information from outside the const block as well. This is a frequently requested feature to the initial implementation (e.g. rust-lang#89964). The inference is implemented in rust-lang#89561 and is done by treating inline const similar to a closure and therefore share inference context with its parent body. This allows code like: ```rust let v: Vec<i32> = const { Vec::new() }; ``` Another enhancement that differs from the RFC is that we currently allow inline consts to reference generic parameters. This is implemented in rust-lang#96557. This allows code like: ```rust fn create_none_array<T, const N: usize>() -> [Option<T>; N] { [const { None::<T> }; N] } ``` This enhancement also makes inline const usable as static asserts: ```rust fn require_zst<T>() { const { assert!(std::mem::size_of::<T>() == 0) } } ``` ## Documentation Reference: rust-lang/reference#1295 ## Unresolved issues We still have a few issues that are not resolved, but I don't think it necessarily has to block stabilisation: * expr fragment specifier issue: rust-lang#86730 * ~~`const {}` behaves similar to `async {}` but not to `{}` and `unsafe {}` (they are treated as `ExpressionWithoutBlock` rather than `ExpressionWithBlock`): https://rust-lang.zulipchat.com/#narrow/stream/213817-t-lang/topic/const.20blocks.20differ.20from.20normal.20and.20from.20unsafe.20blocks/near/290229453~~ ## Tests There are a few tests in https://github.com/rust-lang/rust/tree/master/src/test/ui/inline-const
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Apr 22, 2024
Stabilise inline_const # Stabilisation Report ## Summary This PR will stabilise `inline_const` feature in expression position. `inline_const_pat` is still unstable and will *not* be stabilised. The feature will allow code like this: ```rust foo(const { 1 + 1 }) ``` which is roughly desugared into ```rust struct Foo; impl Foo { const FOO: i32 = 1 + 1; } foo(Foo::FOO) ``` This feature is from rust-lang/rfcs#2920 and is tracked in rust-lang#76001 (the tracking issue should *not* be closed as it needs to track inline const in pattern position). The initial implementation is done in rust-lang#77124. ## Difference from RFC There are two major differences (enhancements) as implemented from the RFC. First thing is that the RFC says that the type of an inline const block inferred from the content *within* it, but we currently can infer the type using the information from outside the const block as well. This is a frequently requested feature to the initial implementation (e.g. rust-lang#89964). The inference is implemented in rust-lang#89561 and is done by treating inline const similar to a closure and therefore share inference context with its parent body. This allows code like: ```rust let v: Vec<i32> = const { Vec::new() }; ``` Another enhancement that differs from the RFC is that we currently allow inline consts to reference generic parameters. This is implemented in rust-lang#96557. This allows code like: ```rust fn create_none_array<T, const N: usize>() -> [Option<T>; N] { [const { None::<T> }; N] } ``` This enhancement also makes inline const usable as static asserts: ```rust fn require_zst<T>() { const { assert!(std::mem::size_of::<T>() == 0) } } ``` ## Documentation Reference: rust-lang/reference#1295 ## Unresolved issues We still have a few issues that are not resolved, but I don't think it necessarily has to block stabilisation: * expr fragment specifier issue: rust-lang#86730 * ~~`const {}` behaves similar to `async {}` but not to `{}` and `unsafe {}` (they are treated as `ExpressionWithoutBlock` rather than `ExpressionWithBlock`): https://rust-lang.zulipchat.com/#narrow/stream/213817-t-lang/topic/const.20blocks.20differ.20from.20normal.20and.20from.20unsafe.20blocks/near/290229453~~ ## Tests There are a few tests in https://github.com/rust-lang/rust/tree/master/src/test/ui/inline-const
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Apr 24, 2024
Stabilise inline_const # Stabilisation Report ## Summary This PR will stabilise `inline_const` feature in expression position. `inline_const_pat` is still unstable and will *not* be stabilised. The feature will allow code like this: ```rust foo(const { 1 + 1 }) ``` which is roughly desugared into ```rust struct Foo; impl Foo { const FOO: i32 = 1 + 1; } foo(Foo::FOO) ``` This feature is from rust-lang/rfcs#2920 and is tracked in rust-lang#76001 (the tracking issue should *not* be closed as it needs to track inline const in pattern position). The initial implementation is done in rust-lang#77124. ## Difference from RFC There are two major differences (enhancements) as implemented from the RFC. First thing is that the RFC says that the type of an inline const block inferred from the content *within* it, but we currently can infer the type using the information from outside the const block as well. This is a frequently requested feature to the initial implementation (e.g. rust-lang#89964). The inference is implemented in rust-lang#89561 and is done by treating inline const similar to a closure and therefore share inference context with its parent body. This allows code like: ```rust let v: Vec<i32> = const { Vec::new() }; ``` Another enhancement that differs from the RFC is that we currently allow inline consts to reference generic parameters. This is implemented in rust-lang#96557. This allows code like: ```rust fn create_none_array<T, const N: usize>() -> [Option<T>; N] { [const { None::<T> }; N] } ``` This enhancement also makes inline const usable as static asserts: ```rust fn require_zst<T>() { const { assert!(std::mem::size_of::<T>() == 0) } } ``` ## Documentation Reference: rust-lang/reference#1295 ## Unresolved issues We still have a few issues that are not resolved, but I don't think it necessarily has to block stabilisation: * expr fragment specifier issue: rust-lang#86730 * ~~`const {}` behaves similar to `async {}` but not to `{}` and `unsafe {}` (they are treated as `ExpressionWithoutBlock` rather than `ExpressionWithBlock`): https://rust-lang.zulipchat.com/#narrow/stream/213817-t-lang/topic/const.20blocks.20differ.20from.20normal.20and.20from.20unsafe.20blocks/near/290229453~~ ## Tests There are a few tests in https://github.com/rust-lang/rust/tree/master/src/test/ui/inline-const
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Apr 24, 2024
Stabilise inline_const # Stabilisation Report ## Summary This PR will stabilise `inline_const` feature in expression position. `inline_const_pat` is still unstable and will *not* be stabilised. The feature will allow code like this: ```rust foo(const { 1 + 1 }) ``` which is roughly desugared into ```rust struct Foo; impl Foo { const FOO: i32 = 1 + 1; } foo(Foo::FOO) ``` This feature is from rust-lang/rfcs#2920 and is tracked in rust-lang#76001 (the tracking issue should *not* be closed as it needs to track inline const in pattern position). The initial implementation is done in rust-lang#77124. ## Difference from RFC There are two major differences (enhancements) as implemented from the RFC. First thing is that the RFC says that the type of an inline const block inferred from the content *within* it, but we currently can infer the type using the information from outside the const block as well. This is a frequently requested feature to the initial implementation (e.g. rust-lang#89964). The inference is implemented in rust-lang#89561 and is done by treating inline const similar to a closure and therefore share inference context with its parent body. This allows code like: ```rust let v: Vec<i32> = const { Vec::new() }; ``` Another enhancement that differs from the RFC is that we currently allow inline consts to reference generic parameters. This is implemented in rust-lang#96557. This allows code like: ```rust fn create_none_array<T, const N: usize>() -> [Option<T>; N] { [const { None::<T> }; N] } ``` This enhancement also makes inline const usable as static asserts: ```rust fn require_zst<T>() { const { assert!(std::mem::size_of::<T>() == 0) } } ``` ## Documentation Reference: rust-lang/reference#1295 ## Unresolved issues We still have a few issues that are not resolved, but I don't think it necessarily has to block stabilisation: * expr fragment specifier issue: rust-lang#86730 * ~~`const {}` behaves similar to `async {}` but not to `{}` and `unsafe {}` (they are treated as `ExpressionWithoutBlock` rather than `ExpressionWithBlock`): https://rust-lang.zulipchat.com/#narrow/stream/213817-t-lang/topic/const.20blocks.20differ.20from.20normal.20and.20from.20unsafe.20blocks/near/290229453~~ ## Tests There are a few tests in https://github.com/rust-lang/rust/tree/master/src/test/ui/inline-const
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Apr 24, 2024
Stabilise inline_const # Stabilisation Report ## Summary This PR will stabilise `inline_const` feature in expression position. `inline_const_pat` is still unstable and will *not* be stabilised. The feature will allow code like this: ```rust foo(const { 1 + 1 }) ``` which is roughly desugared into ```rust struct Foo; impl Foo { const FOO: i32 = 1 + 1; } foo(Foo::FOO) ``` This feature is from rust-lang/rfcs#2920 and is tracked in rust-lang#76001 (the tracking issue should *not* be closed as it needs to track inline const in pattern position). The initial implementation is done in rust-lang#77124. ## Difference from RFC There are two major differences (enhancements) as implemented from the RFC. First thing is that the RFC says that the type of an inline const block inferred from the content *within* it, but we currently can infer the type using the information from outside the const block as well. This is a frequently requested feature to the initial implementation (e.g. rust-lang#89964). The inference is implemented in rust-lang#89561 and is done by treating inline const similar to a closure and therefore share inference context with its parent body. This allows code like: ```rust let v: Vec<i32> = const { Vec::new() }; ``` Another enhancement that differs from the RFC is that we currently allow inline consts to reference generic parameters. This is implemented in rust-lang#96557. This allows code like: ```rust fn create_none_array<T, const N: usize>() -> [Option<T>; N] { [const { None::<T> }; N] } ``` This enhancement also makes inline const usable as static asserts: ```rust fn require_zst<T>() { const { assert!(std::mem::size_of::<T>() == 0) } } ``` ## Documentation Reference: rust-lang/reference#1295 ## Unresolved issues We still have a few issues that are not resolved, but I don't think it necessarily has to block stabilisation: * expr fragment specifier issue: rust-lang#86730 * ~~`const {}` behaves similar to `async {}` but not to `{}` and `unsafe {}` (they are treated as `ExpressionWithoutBlock` rather than `ExpressionWithBlock`): https://rust-lang.zulipchat.com/#narrow/stream/213817-t-lang/topic/const.20blocks.20differ.20from.20normal.20and.20from.20unsafe.20blocks/near/290229453~~ ## Tests There are a few tests in https://github.com/rust-lang/rust/tree/master/src/test/ui/inline-const
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Apr 24, 2024
Stabilise inline_const # Stabilisation Report ## Summary This PR will stabilise `inline_const` feature in expression position. `inline_const_pat` is still unstable and will *not* be stabilised. The feature will allow code like this: ```rust foo(const { 1 + 1 }) ``` which is roughly desugared into ```rust struct Foo; impl Foo { const FOO: i32 = 1 + 1; } foo(Foo::FOO) ``` This feature is from rust-lang/rfcs#2920 and is tracked in rust-lang#76001 (the tracking issue should *not* be closed as it needs to track inline const in pattern position). The initial implementation is done in rust-lang#77124. ## Difference from RFC There are two major differences (enhancements) as implemented from the RFC. First thing is that the RFC says that the type of an inline const block inferred from the content *within* it, but we currently can infer the type using the information from outside the const block as well. This is a frequently requested feature to the initial implementation (e.g. rust-lang#89964). The inference is implemented in rust-lang#89561 and is done by treating inline const similar to a closure and therefore share inference context with its parent body. This allows code like: ```rust let v: Vec<i32> = const { Vec::new() }; ``` Another enhancement that differs from the RFC is that we currently allow inline consts to reference generic parameters. This is implemented in rust-lang#96557. This allows code like: ```rust fn create_none_array<T, const N: usize>() -> [Option<T>; N] { [const { None::<T> }; N] } ``` This enhancement also makes inline const usable as static asserts: ```rust fn require_zst<T>() { const { assert!(std::mem::size_of::<T>() == 0) } } ``` ## Documentation Reference: rust-lang/reference#1295 ## Unresolved issues We still have a few issues that are not resolved, but I don't think it necessarily has to block stabilisation: * expr fragment specifier issue: rust-lang#86730 * ~~`const {}` behaves similar to `async {}` but not to `{}` and `unsafe {}` (they are treated as `ExpressionWithoutBlock` rather than `ExpressionWithBlock`): https://rust-lang.zulipchat.com/#narrow/stream/213817-t-lang/topic/const.20blocks.20differ.20from.20normal.20and.20from.20unsafe.20blocks/near/290229453~~ ## Tests There are a few tests in https://github.com/rust-lang/rust/tree/master/src/test/ui/inline-const
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Apr 24, 2024
Stabilise inline_const # Stabilisation Report ## Summary This PR will stabilise `inline_const` feature in expression position. `inline_const_pat` is still unstable and will *not* be stabilised. The feature will allow code like this: ```rust foo(const { 1 + 1 }) ``` which is roughly desugared into ```rust struct Foo; impl Foo { const FOO: i32 = 1 + 1; } foo(Foo::FOO) ``` This feature is from rust-lang/rfcs#2920 and is tracked in rust-lang#76001 (the tracking issue should *not* be closed as it needs to track inline const in pattern position). The initial implementation is done in rust-lang#77124. ## Difference from RFC There are two major differences (enhancements) as implemented from the RFC. First thing is that the RFC says that the type of an inline const block inferred from the content *within* it, but we currently can infer the type using the information from outside the const block as well. This is a frequently requested feature to the initial implementation (e.g. rust-lang#89964). The inference is implemented in rust-lang#89561 and is done by treating inline const similar to a closure and therefore share inference context with its parent body. This allows code like: ```rust let v: Vec<i32> = const { Vec::new() }; ``` Another enhancement that differs from the RFC is that we currently allow inline consts to reference generic parameters. This is implemented in rust-lang#96557. This allows code like: ```rust fn create_none_array<T, const N: usize>() -> [Option<T>; N] { [const { None::<T> }; N] } ``` This enhancement also makes inline const usable as static asserts: ```rust fn require_zst<T>() { const { assert!(std::mem::size_of::<T>() == 0) } } ``` ## Documentation Reference: rust-lang/reference#1295 ## Unresolved issues We still have a few issues that are not resolved, but I don't think it necessarily has to block stabilisation: * expr fragment specifier issue: rust-lang#86730 * ~~`const {}` behaves similar to `async {}` but not to `{}` and `unsafe {}` (they are treated as `ExpressionWithoutBlock` rather than `ExpressionWithBlock`): https://rust-lang.zulipchat.com/#narrow/stream/213817-t-lang/topic/const.20blocks.20differ.20from.20normal.20and.20from.20unsafe.20blocks/near/290229453~~ ## Tests There are a few tests in https://github.com/rust-lang/rust/tree/master/src/test/ui/inline-const
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Labels
C-bug
Category: This is a bug.
F-inline_const
Inline constants (aka: const blocks, const expressions, anonymous constants)
I tried this code: https://play.rust-lang.org/?version=nightly&mode=debug&edition=2018&gist=b628c24337168091d1c20e62ff6e31e8
I expected to see this happen: It compiles, the same as the following (without the
const{}
) does https://play.rust-lang.org/?version=nightly&mode=debug&edition=2018&gist=2da5b1d9926024223ba6dff77a647f17Instead, this happened: type inference fails
(Spotted after looking at https://internals.rust-lang.org/t/should-clippy-warn-about-function-calls-outside-closures-if-those-are-const-answered/15452/4?u=scottmcm)
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