Auto merge of #58403 - eddyb:requalify, r=oli-obk

rustc_mir: split qualify_consts' "value qualification" bitflags into separate computations.

Prerequisite for computing those bits through a dataflow algorithm ~~(which I might do in this PR later)~~.

This PR should not change behavior overall, other than treating `simd_shuffle*` identically to `#[rustc_args_required_const]` (maybe we should just have `#[rustc_args_required_const]` on the intrinsic imports of `simd_shuffle*`? cc @gnzlbg)

cc @oli-obk @alexreg

Cargo.lock

@@ -2822,7 +2822,6 @@ name = "rustc_mir"
 version = "0.0.0"
 dependencies = [
  "arena 0.0.0",
- "bitflags 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "byteorder 1.2.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "either 1.5.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "graphviz 0.0.0",

src/librustc_mir/Cargo.toml

@@ -11,7 +11,6 @@ crate-type = ["dylib"]
 
 [dependencies]
 arena = { path = "../libarena" }
-bitflags = "1.0"
 either = "1.5.0"
 dot = { path = "../libgraphviz", package = "graphviz" }
 log = "0.4"

src/test/ui/error-codes/E0017.nll.stderr

@@ -4,18 +4,18 @@ error[E0017]: references in constants may only refer to immutable values
 LL | const CR: &'static mut i32 = &mut C; //~ ERROR E0017
    |                              ^^^^^^ constants require immutable values
 
-error: cannot mutate statics in the initializer of another static
-  --> $DIR/E0017.rs:5:39
-   |
-LL | static STATIC_REF: &'static mut i32 = &mut X; //~ ERROR E0017
-   |                                       ^^^^^^
-
 error[E0017]: references in statics may only refer to immutable values
   --> $DIR/E0017.rs:5:39
    |
 LL | static STATIC_REF: &'static mut i32 = &mut X; //~ ERROR E0017
    |                                       ^^^^^^ statics require immutable values
 
+error: cannot mutate statics in the initializer of another static
+  --> $DIR/E0017.rs:5:39
+   |
+LL | static STATIC_REF: &'static mut i32 = &mut X; //~ ERROR E0017
+   |                                       ^^^^^^
+
 error[E0596]: cannot borrow immutable static item `X` as mutable
   --> $DIR/E0017.rs:5:39
    |

src/test/ui/error-codes/E0017.stderr

@@ -4,18 +4,18 @@ error[E0017]: references in constants may only refer to immutable values
 LL | const CR: &'static mut i32 = &mut C; //~ ERROR E0017
    |                              ^^^^^^ constants require immutable values
 
-error: cannot mutate statics in the initializer of another static
-  --> $DIR/E0017.rs:5:39
-   |
-LL | static STATIC_REF: &'static mut i32 = &mut X; //~ ERROR E0017
-   |                                       ^^^^^^
-
 error[E0017]: references in statics may only refer to immutable values
   --> $DIR/E0017.rs:5:39
    |
 LL | static STATIC_REF: &'static mut i32 = &mut X; //~ ERROR E0017
    |                                       ^^^^^^ statics require immutable values
 
+error: cannot mutate statics in the initializer of another static
+  --> $DIR/E0017.rs:5:39
+   |
+LL | static STATIC_REF: &'static mut i32 = &mut X; //~ ERROR E0017
+   |                                       ^^^^^^
+
 error[E0596]: cannot borrow immutable static item as mutable
   --> $DIR/E0017.rs:5:44
    |

src/test/ui/error-codes/E0388.nll.stderr

@@ -4,18 +4,18 @@ error[E0017]: references in constants may only refer to immutable values
 LL | const CR: &'static mut i32 = &mut C; //~ ERROR E0017
    |                              ^^^^^^ constants require immutable values
 
-error: cannot mutate statics in the initializer of another static
-  --> $DIR/E0388.rs:5:39
-   |
-LL | static STATIC_REF: &'static mut i32 = &mut X; //~ ERROR E0017
-   |                                       ^^^^^^
-
 error[E0017]: references in statics may only refer to immutable values
   --> $DIR/E0388.rs:5:39
    |
 LL | static STATIC_REF: &'static mut i32 = &mut X; //~ ERROR E0017
    |                                       ^^^^^^ statics require immutable values
 
+error: cannot mutate statics in the initializer of another static
+  --> $DIR/E0388.rs:5:39
+   |
+LL | static STATIC_REF: &'static mut i32 = &mut X; //~ ERROR E0017
+   |                                       ^^^^^^
+
 error[E0596]: cannot borrow immutable static item `X` as mutable
   --> $DIR/E0388.rs:5:39
    |

src/test/ui/error-codes/E0388.stderr

@@ -4,18 +4,18 @@ error[E0017]: references in constants may only refer to immutable values
 LL | const CR: &'static mut i32 = &mut C; //~ ERROR E0017
    |                              ^^^^^^ constants require immutable values
 
-error: cannot mutate statics in the initializer of another static
-  --> $DIR/E0388.rs:5:39
-   |
-LL | static STATIC_REF: &'static mut i32 = &mut X; //~ ERROR E0017
-   |                                       ^^^^^^
-
 error[E0017]: references in statics may only refer to immutable values
   --> $DIR/E0388.rs:5:39
    |
 LL | static STATIC_REF: &'static mut i32 = &mut X; //~ ERROR E0017
    |                                       ^^^^^^ statics require immutable values
 
+error: cannot mutate statics in the initializer of another static
+  --> $DIR/E0388.rs:5:39
+   |
+LL | static STATIC_REF: &'static mut i32 = &mut X; //~ ERROR E0017
+   |                                       ^^^^^^
+
 error[E0596]: cannot borrow immutable static item as mutable
   --> $DIR/E0388.rs:5:44
    |

src/test/ui/issues/issue-17718-const-bad-values.stderr

@@ -4,18 +4,18 @@ error[E0017]: references in constants may only refer to immutable values
 LL | const C1: &'static mut [usize] = &mut [];
    |                                  ^^^^^^^ constants require immutable values
 
-error[E0013]: constants cannot refer to statics, use a constant instead
-  --> $DIR/issue-17718-const-bad-values.rs:5:41
-   |
-LL | const C2: &'static mut usize = unsafe { &mut S };
-   |                                         ^^^^^^
-
 error[E0017]: references in constants may only refer to immutable values
   --> $DIR/issue-17718-const-bad-values.rs:5:41
    |
 LL | const C2: &'static mut usize = unsafe { &mut S };
    |                                         ^^^^^^ constants require immutable values
 
+error[E0013]: constants cannot refer to statics, use a constant instead
+  --> $DIR/issue-17718-const-bad-values.rs:5:41
+   |
+LL | const C2: &'static mut usize = unsafe { &mut S };
+   |                                         ^^^^^^
+
 error: aborting due to 3 previous errors
 
 Some errors occurred: E0013, E0017.