Auto merge of #46882 - oli-obk:miri3, r=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

1 files changed, 10 insertions, 0 deletions

diff --git a/src/test/compile-fail/const-integer-bool-ops.rs b/src/test/compile-fail/const-integer-bool-ops.rs
index 29bc665a22e..3065122af6a 100644
--- a/src/test/compile-fail/const-integer-bool-ops.rs
+++ b/src/test/compile-fail/const-integer-bool-ops.rs
@@ -16,6 +16,7 @@ const X: usize = 42 && 39;
 //~| ERROR mismatched types
 //~| expected usize, found bool
 const ARR: [i32; X] = [99; 34];
+//~^ ERROR constant evaluation error
 
 const X1: usize = 42 || 39;
 //~^ ERROR mismatched types
@@ -25,6 +26,7 @@ const X1: usize = 42 || 39;
 //~| ERROR mismatched types
 //~| expected usize, found bool
 const ARR1: [i32; X1] = [99; 47];
+//~^ ERROR constant evaluation error
 
 const X2: usize = -42 || -39;
 //~^ ERROR mismatched types
@@ -34,6 +36,7 @@ const X2: usize = -42 || -39;
 //~| ERROR mismatched types
 //~| expected usize, found bool
 const ARR2: [i32; X2] = [99; 18446744073709551607];
+//~^ ERROR constant evaluation error
 
 const X3: usize = -42 && -39;
 //~^ ERROR mismatched types
@@ -43,36 +46,43 @@ const X3: usize = -42 && -39;
 //~| ERROR mismatched types
 //~| expected usize, found bool
 const ARR3: [i32; X3] = [99; 6];
+//~^ ERROR constant evaluation error
 
 const Y: usize = 42.0 == 42.0;
 //~^ ERROR mismatched types
 //~| expected usize, found bool
 const ARRR: [i32; Y] = [99; 1];
+//~^ ERROR constant evaluation error
 
 const Y1: usize = 42.0 >= 42.0;
 //~^ ERROR mismatched types
 //~| expected usize, found bool
 const ARRR1: [i32; Y1] = [99; 1];
+//~^ ERROR constant evaluation error
 
 const Y2: usize = 42.0 <= 42.0;
 //~^ ERROR mismatched types
 //~| expected usize, found bool
 const ARRR2: [i32; Y2] = [99; 1];
+//~^ ERROR constant evaluation error
 
 const Y3: usize = 42.0 > 42.0;
 //~^ ERROR mismatched types
 //~| expected usize, found bool
 const ARRR3: [i32; Y3] = [99; 0];
+//~^ ERROR constant evaluation error
 
 const Y4: usize = 42.0 < 42.0;
 //~^ ERROR mismatched types
 //~| expected usize, found bool
 const ARRR4: [i32; Y4] = [99; 0];
+//~^ ERROR constant evaluation error
 
 const Y5: usize = 42.0 != 42.0;
 //~^ ERROR mismatched types
 //~| expected usize, found bool
 const ARRR5: [i32; Y5] = [99; 0];
+//~^ ERROR constant evaluation error
 
 fn main() {
     let _ = ARR;