Auto merge of #75697 - lzutao:mir-dumb-const-prefix, r=oli-obk

Suppress "const" prefix of FnDef constants in MIR dump

I [was asked][1] to suppress the `const` infront of `FnDef`.
I tried to suppress comments for other types, but turned out that `const ()` and `()` is different: #75697 (comment)

[1]: #75670 (comment)

Author: bors

src/librustc_middle/mir/mod.rs

@@ -2452,7 +2452,10 @@ impl<'tcx> Debug for Constant<'tcx> {
 
 impl<'tcx> Display for Constant<'tcx> {
     fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
-        write!(fmt, "const ")?;
+        match self.literal.ty.kind {
+            ty::FnDef(..) => {}
+            _ => write!(fmt, "const ")?,
+        }
         pretty_print_const(self.literal, fmt, true)
     }
 }

src/test/mir-opt/array_index_is_temporary.main.SimplifyCfg-elaborate-drops.after.mir.32bit

@@ -36,7 +36,7 @@ fn main() -> () {
         StorageLive(_5);                 // scope 3 at $DIR/array-index-is-temporary.rs:16:12: 16:29
         StorageLive(_6);                 // scope 4 at $DIR/array-index-is-temporary.rs:16:25: 16:26
         _6 = _3;                         // scope 4 at $DIR/array-index-is-temporary.rs:16:25: 16:26
-        _5 = const foo(move _6) -> bb1;  // scope 4 at $DIR/array-index-is-temporary.rs:16:21: 16:27
+        _5 = foo(move _6) -> bb1;        // scope 4 at $DIR/array-index-is-temporary.rs:16:21: 16:27
                                          // mir::Constant
                                          // + span: $DIR/array-index-is-temporary.rs:16:21: 16:24
                                          // + literal: Const { ty: unsafe fn(*mut usize) -> u32 {foo}, val: Value(Scalar(<ZST>)) }

src/test/mir-opt/array_index_is_temporary.main.SimplifyCfg-elaborate-drops.after.mir.64bit

@@ -36,7 +36,7 @@ fn main() -> () {
         StorageLive(_5);                 // scope 3 at $DIR/array-index-is-temporary.rs:16:12: 16:29
         StorageLive(_6);                 // scope 4 at $DIR/array-index-is-temporary.rs:16:25: 16:26
         _6 = _3;                         // scope 4 at $DIR/array-index-is-temporary.rs:16:25: 16:26
-        _5 = const foo(move _6) -> bb1;  // scope 4 at $DIR/array-index-is-temporary.rs:16:21: 16:27
+        _5 = foo(move _6) -> bb1;        // scope 4 at $DIR/array-index-is-temporary.rs:16:21: 16:27
                                          // mir::Constant
                                          // + span: $DIR/array-index-is-temporary.rs:16:21: 16:24
                                          // + literal: Const { ty: unsafe fn(*mut usize) -> u32 {foo}, val: Value(Scalar(<ZST>)) }

src/test/mir-opt/box_expr.main.ElaborateDrops.before.mir

@@ -14,7 +14,7 @@ fn main() -> () {
         StorageLive(_1);                 // scope 0 at $DIR/box_expr.rs:7:9: 7:10
         StorageLive(_2);                 // scope 0 at $DIR/box_expr.rs:7:13: 7:25
         _2 = Box(S);                     // scope 0 at $DIR/box_expr.rs:7:13: 7:25
-        (*_2) = const S::new() -> [return: bb2, unwind: bb3]; // scope 0 at $DIR/box_expr.rs:7:17: 7:25
+        (*_2) = S::new() -> [return: bb2, unwind: bb3]; // scope 0 at $DIR/box_expr.rs:7:17: 7:25
                                          // mir::Constant
                                          // + span: $DIR/box_expr.rs:7:17: 7:23
                                          // + literal: Const { ty: fn() -> S {S::new}, val: Value(Scalar(<ZST>)) }
@@ -38,7 +38,7 @@ fn main() -> () {
         StorageLive(_3);                 // scope 1 at $DIR/box_expr.rs:8:5: 8:12
         StorageLive(_4);                 // scope 1 at $DIR/box_expr.rs:8:10: 8:11
         _4 = move _1;                    // scope 1 at $DIR/box_expr.rs:8:10: 8:11
-        _3 = const std::mem::drop::<std::boxed::Box<S>>(move _4) -> [return: bb5, unwind: bb7]; // scope 1 at $DIR/box_expr.rs:8:5: 8:12
+        _3 = std::mem::drop::<std::boxed::Box<S>>(move _4) -> [return: bb5, unwind: bb7]; // scope 1 at $DIR/box_expr.rs:8:5: 8:12
                                          // mir::Constant
                                          // + span: $DIR/box_expr.rs:8:5: 8:9
                                          // + literal: Const { ty: fn(std::boxed::Box<S>) {std::mem::drop::<std::boxed::Box<S>>}, val: Value(Scalar(<ZST>)) }

src/test/mir-opt/const_promotion_extern_static.BAR.PromoteTemps.diff

@@ -33,7 +33,7 @@
 +                                          // + literal: Const { ty: &[&i32; 1], val: Unevaluated(WithOptConstParam { did: DefId(0:6 ~ const_promotion_extern_static[317d]::BAR[0]), const_param_did: None }, [], Some(promoted[0])) }
 +         _2 = &(*_6);                     // scope 0 at $DIR/const-promotion-extern-static.rs:9:31: 9:35
           _1 = move _2 as &[&i32] (Pointer(Unsize)); // scope 0 at $DIR/const-promotion-extern-static.rs:9:31: 9:35
-          _0 = const core::slice::<impl [&i32]>::as_ptr(move _1) -> [return: bb2, unwind: bb1]; // scope 0 at $DIR/const-promotion-extern-static.rs:9:31: 9:44
+          _0 = core::slice::<impl [&i32]>::as_ptr(move _1) -> [return: bb2, unwind: bb1]; // scope 0 at $DIR/const-promotion-extern-static.rs:9:31: 9:44
                                            // mir::Constant
                                            // + span: $DIR/const-promotion-extern-static.rs:9:36: 9:42
                                            // + literal: Const { ty: for<'r> fn(&'r [&i32]) -> *const &i32 {core::slice::<impl [&i32]>::as_ptr}, val: Value(Scalar(<ZST>)) }

src/test/mir-opt/const_promotion_extern_static.FOO.PromoteTemps.diff

@@ -35,7 +35,7 @@
 +                                          // + literal: Const { ty: &[&i32; 1], val: Unevaluated(WithOptConstParam { did: DefId(0:7 ~ const_promotion_extern_static[317d]::FOO[0]), const_param_did: None }, [], Some(promoted[0])) }
 +         _2 = &(*_6);                     // scope 0 at $DIR/const-promotion-extern-static.rs:13:31: 13:46
           _1 = move _2 as &[&i32] (Pointer(Unsize)); // scope 0 at $DIR/const-promotion-extern-static.rs:13:31: 13:46
-          _0 = const core::slice::<impl [&i32]>::as_ptr(move _1) -> [return: bb2, unwind: bb1]; // scope 0 at $DIR/const-promotion-extern-static.rs:13:31: 13:55
+          _0 = core::slice::<impl [&i32]>::as_ptr(move _1) -> [return: bb2, unwind: bb1]; // scope 0 at $DIR/const-promotion-extern-static.rs:13:31: 13:55
                                            // mir::Constant
                                            // + span: $DIR/const-promotion-extern-static.rs:13:47: 13:53
                                            // + literal: Const { ty: for<'r> fn(&'r [&i32]) -> *const &i32 {core::slice::<impl [&i32]>::as_ptr}, val: Value(Scalar(<ZST>)) }

src/test/mir-opt/const_prop/const_prop_fails_gracefully.main.ConstProp.diff

@@ -30,7 +30,7 @@
           StorageLive(_4);                 // scope 1 at $DIR/const_prop_fails_gracefully.rs:8:5: 8:12
           StorageLive(_5);                 // scope 1 at $DIR/const_prop_fails_gracefully.rs:8:10: 8:11
           _5 = _1;                         // scope 1 at $DIR/const_prop_fails_gracefully.rs:8:10: 8:11
-          _4 = const read(move _5) -> bb1; // scope 1 at $DIR/const_prop_fails_gracefully.rs:8:5: 8:12
+          _4 = read(move _5) -> bb1;       // scope 1 at $DIR/const_prop_fails_gracefully.rs:8:5: 8:12
                                            // mir::Constant
                                            // + span: $DIR/const_prop_fails_gracefully.rs:8:5: 8:9
                                            // + literal: Const { ty: fn(usize) {read}, val: Value(Scalar(<ZST>)) }

src/test/mir-opt/const_prop/control_flow_simplification.hello.ConstProp.diff

@@ -22,7 +22,7 @@
 
       bb2: {
           StorageLive(_2);                 // scope 0 at $SRC_DIR/std/src/macros.rs:LL:COL
-          const std::rt::begin_panic::<&str>(const "explicit panic"); // scope 0 at $SRC_DIR/std/src/macros.rs:LL:COL
+          std::rt::begin_panic::<&str>(const "explicit panic"); // scope 0 at $SRC_DIR/std/src/macros.rs:LL:COL
                                            // mir::Constant
                                            // + span: $SRC_DIR/std/src/macros.rs:LL:COL
                                            // + literal: Const { ty: fn(&str) -> ! {std::rt::begin_panic::<&str>}, val: Value(Scalar(<ZST>)) }

src/test/mir-opt/const_prop/issue_66971.main.ConstProp.diff

@@ -16,7 +16,7 @@
           (_2.1: u8) = const 0_u8;         // scope 0 at $DIR/issue-66971.rs:16:12: 16:22
           (_2.2: u8) = const 0_u8;         // scope 0 at $DIR/issue-66971.rs:16:12: 16:22
           StorageDead(_3);                 // scope 0 at $DIR/issue-66971.rs:16:21: 16:22
-          _1 = const encode(move _2) -> bb1; // scope 0 at $DIR/issue-66971.rs:16:5: 16:23
+          _1 = encode(move _2) -> bb1;     // scope 0 at $DIR/issue-66971.rs:16:5: 16:23
                                            // mir::Constant
                                            // + span: $DIR/issue-66971.rs:16:5: 16:11
                                            // + literal: Const { ty: fn(((), u8, u8)) {encode}, val: Value(Scalar(<ZST>)) }

src/test/mir-opt/const_prop/issue_67019.main.ConstProp.diff

@@ -22,7 +22,7 @@
 +                                          // + span: $DIR/issue-67019.rs:11:10: 11:19
 +                                          // + literal: Const { ty: (u8, u8), val: Value(ByRef { alloc: Allocation { bytes: [1, 2], relocations: Relocations(SortedMap { data: [] }), init_mask: InitMask { blocks: [3], len: Size { raw: 2 } }, size: Size { raw: 2 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, offset: Size { raw: 0 } }) }
           StorageDead(_3);                 // scope 0 at $DIR/issue-67019.rs:11:18: 11:19
-          _1 = const test(move _2) -> bb1; // scope 0 at $DIR/issue-67019.rs:11:5: 11:20
+          _1 = test(move _2) -> bb1;       // scope 0 at $DIR/issue-67019.rs:11:5: 11:20
                                            // mir::Constant
                                            // + span: $DIR/issue-67019.rs:11:5: 11:9
                                            // + literal: Const { ty: fn(((u8, u8),)) {test}, val: Value(Scalar(<ZST>)) }