Consteval cannot handle non-scalar identity casts #37448

nagisa · 2016-10-28T14:48:05Z

struct A;
&A as A;

results in

warning: can't cast this type, #[warn(const_err)] on by default
 --> <anon>:3:5
  |
3 |     A as A;
  |     ^^^^^^

The text was updated successfully, but these errors were encountered:

@eddyb

Replace all const evaluation with miri * error reporting in constants prints a stacktrace through all called const fns * Trivial constant propagation and folding in MIR (always active, irrelevant of the optimization level) * can now use floating constants in patterns (previously only floating point literals were allowed) * the future compat lint is still produced for both cases * can index into constant arrays during const eval (previously feature gated) * can create a constant union value with field `a` and read from field `b` * can dereference references into constants * can create references inside constants (`const X: &u32 = &22`) * Tuple struct constructors can be used in constants * regression in const eval errors spans (some of these need improvements in mir debug info) * can cast floats to ints and vice versa (in constants, and even nan/inf constants) * Mir dump prints false/true instead of 0u8/1u8 * `1i8 >> [8][0]` does not lint about exceeding bitshifts anymore. * Needs const propagation across projections * `foo[I]` produces a const eval lint if `foo: [T; N]` and `N < I` * Essentially all builtin panics produce lints if they can be statically proven to trigger at runtime. This is on a best effort basis, so there might be some complex cases that don't trigger. (The runtime panic stays there, irrelevant of whether the lint is produced or not) fixes #34997 (stack overflow with many constants) fixes #25574 (deref byte strings in patterns) fixes #27918 (broken mir ICE) fixes #46114 (ICE on struct constructors in patterns) fixes #37448 (`SomeStruct { foo } as SomeStruct`) fixes #43754 (`return` in const fn) fixes #41898 (tuple struct constructors) fixes #31364 (infinite recursion with const fn, fixed by miri's recursion limit) closes #29947 (const indexing stabilization) r? @eddyb

@eddyb

Replace all const evaluation with miri * error reporting in constants prints a stacktrace through all called const fns * Trivial constant propagation and folding in MIR (always active, irrelevant of the optimization level) * can now use floating constants in patterns (previously only floating point literals were allowed) * the future compat lint is still produced for both cases * can index into constant arrays during const eval (previously feature gated) * can create a constant union value with field `a` and read from field `b` * can dereference references into constants * can create references inside constants (`const X: &u32 = &22`) * Tuple struct constructors can be used in constants * regression in const eval errors spans (some of these need improvements in mir debug info) * can cast floats to ints and vice versa (in constants, and even nan/inf constants) * Mir dump prints false/true instead of 0u8/1u8 * `1i8 >> [8][0]` does not lint about exceeding bitshifts anymore. * Needs const propagation across projections * `foo[I]` produces a const eval lint if `foo: [T; N]` and `N < I` * Essentially all builtin panics produce lints if they can be statically proven to trigger at runtime. This is on a best effort basis, so there might be some complex cases that don't trigger. (The runtime panic stays there, irrelevant of whether the lint is produced or not) fixes #34997 (stack overflow with many constants) fixes #25574 (deref byte strings in patterns) fixes #27918 (broken mir ICE) fixes #46114 (ICE on struct constructors in patterns) fixes #37448 (`SomeStruct { foo } as SomeStruct`) fixes #43754 (`return` in const fn) fixes #41898 (tuple struct constructors) fixes #31364 (infinite recursion with const fn, fixed by miri's recursion limit) closes #29947 (const indexing stabilization) fixes #45044 (pattern matching repeat expressions) r? @eddyb

@eddyb

Replace all const evaluation with miri * error reporting in constants prints a stacktrace through all called const fns * Trivial constant propagation and folding in MIR (always active, irrelevant of the optimization level) * can now use floating constants in patterns (previously only floating point literals were allowed) * the future compat lint is still produced for both cases * can index into constant arrays during const eval (previously feature gated) * can create a constant union value with field `a` and read from field `b` * can dereference references into constants * can create references inside constants (`const X: &u32 = &22`) * Tuple struct constructors can be used in constants * regression in const eval errors spans (some of these need improvements in mir debug info) * can cast floats to ints and vice versa (in constants, and even nan/inf constants) * Mir dump prints false/true instead of 0u8/1u8 * `1i8 >> [8][0]` does not lint about exceeding bitshifts anymore. * Needs const propagation across projections * `foo[I]` produces a const eval lint if `foo: [T; N]` and `N < I` * Essentially all builtin panics produce lints if they can be statically proven to trigger at runtime. This is on a best effort basis, so there might be some complex cases that don't trigger. (The runtime panic stays there, irrelevant of whether the lint is produced or not) * can use `union`s to implement `transmute` for `Copy` types in constants without a feature gate. With all the greatness and nasal demons that come with this. fixes #34997 (stack overflow with many constants) fixes #25574 (deref byte strings in patterns) fixes #27918 (broken mir ICE) fixes #46114 (ICE on struct constructors in patterns) fixes #37448 (`SomeStruct { foo } as SomeStruct`) fixes #43754 (`return` in const fn) fixes #41898 (tuple struct constructors) fixes #31364 (infinite recursion with const fn, fixed by miri's recursion limit) closes #29947 (const indexing stabilization) fixes #45044 (pattern matching repeat expressions) fixes #47971 (ICE on const fn + references) r? @eddyb

@eddyb

Replace all const evaluation with miri * error reporting in constants prints a stacktrace through all called const fns * Trivial constant propagation and folding in MIR (always active, irrelevant of the optimization level) * can now use floating constants in patterns (previously only floating point literals were allowed) * the future compat lint is still produced for both cases * can index into constant arrays during const eval (previously feature gated) * can create a constant union value with field `a` and read from field `b` * can dereference references into constants * can create references inside constants (`const X: &u32 = &22`) * Tuple struct constructors can be used in constants * regression in const eval errors spans (some of these need improvements in mir debug info) * can cast floats to ints and vice versa (in constants, and even nan/inf constants) * Mir dump prints false/true instead of 0u8/1u8 * `1i8 >> [8][0]` does not lint about exceeding bitshifts anymore. * Needs const propagation across projections * `foo[I]` produces a const eval lint if `foo: [T; N]` and `N < I` * Essentially all builtin panics produce lints if they can be statically proven to trigger at runtime. This is on a best effort basis, so there might be some complex cases that don't trigger. (The runtime panic stays there, irrelevant of whether the lint is produced or not) * can use `union`s to implement `transmute` for `Copy` types in constants without a feature gate. With all the greatness and nasal demons that come with this. * can convert integers to `&'static T` in constants (useful for embedded) fixes #34997 (stack overflow with many constants) fixes #25574 (deref byte strings in patterns) fixes #27918 (broken mir ICE) fixes #46114 (ICE on struct constructors in patterns) fixes #37448 (`SomeStruct { foo } as SomeStruct`) fixes #43754 (`return` in const fn) fixes #41898 (tuple struct constructors) fixes #31364 (infinite recursion with const fn, fixed by miri's recursion limit) closes #29947 (const indexing stabilization) fixes #45044 (pattern matching repeat expressions) fixes #47971 (ICE on const fn + references) fixes #48081 (ICE on cyclic assoc const error) fixes #48746 (nonhelpful error message with unions) r? @eddyb even though 1k loc are added in tests, this PR reduces the loc in this repository by 700

@eddyb

Replace all const evaluation with miri * error reporting in constants prints a stacktrace through all called const fns * Trivial constant propagation and folding in MIR (always active, irrelevant of the optimization level) * can now use floating constants in patterns (previously only floating point literals were allowed) * the future compat lint is still produced for both cases * can index into constant arrays during const eval (previously feature gated) * can create a constant union value with field `a` and read from field `b` * can dereference references into constants * can create references inside constants (`const X: &u32 = &22`) * Tuple struct constructors can be used in constants * regression in const eval errors spans (some of these need improvements in mir debug info) * can cast floats to ints and vice versa (in constants, and even nan/inf constants) * Mir dump prints false/true instead of 0u8/1u8 * `1i8 >> [8][0]` does not lint about exceeding bitshifts anymore. * Needs const propagation across projections * `foo[I]` produces a const eval lint if `foo: [T; N]` and `N < I` * Essentially all builtin panics produce lints if they can be statically proven to trigger at runtime. This is on a best effort basis, so there might be some complex cases that don't trigger. (The runtime panic stays there, irrelevant of whether the lint is produced or not) * can use `union`s to implement `transmute` for `Copy` types in constants without a feature gate. With all the greatness and nasal demons that come with this. * can convert integers to `&'static T` in constants (useful for embedded) fixes #34997 (stack overflow with many constants) fixes #25574 (deref byte strings in patterns) fixes #27918 (broken mir ICE) fixes #46114 (ICE on struct constructors in patterns) fixes #37448 (`SomeStruct { foo } as SomeStruct`) fixes #43754 (`return` in const fn) fixes #41898 (tuple struct constructors) fixes #31364 (infinite recursion with const fn, fixed by miri's recursion limit) closes #29947 (const indexing stabilization) fixes #45044 (pattern matching repeat expressions) fixes #47971 (ICE on const fn + references) fixes #48081 (ICE on cyclic assoc const error) fixes #48746 (nonhelpful error message with unions) r? @eddyb even though 1k loc are added in tests, this PR reduces the loc in this repository by 700

Mark-Simulacrum added the A-const-fn Area: const fn foo(..) {..}. Pure functions which can be applied at compile time. label May 15, 2017

Mark-Simulacrum added the C-bug Category: This is a bug. label Jul 26, 2017

oli-obk mentioned this issue Jan 16, 2018

Replace all const evaluation with miri #46882

Merged

bors closed this as completed in #46882 Mar 8, 2018

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Consteval cannot handle non-scalar identity casts #37448

Consteval cannot handle non-scalar identity casts #37448

nagisa commented Oct 28, 2016 •

edited

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Consteval cannot handle non-scalar identity casts #37448

Consteval cannot handle non-scalar identity casts #37448

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nagisa commented Oct 28, 2016 • edited Loading

nagisa commented Oct 28, 2016 •

edited

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