MGCA: Fix incorrect pretty printing of valtree arrays #151296

Human9000-bit · 2026-01-18T13:01:04Z

add failing test
fix: additional check whether const array could be printed as raw bytes

As I figured out, the problem was in pretty_print_const_valtree, where it tried to print unevaluated consts as if they were evaluated, which resulted in ICE.

rustbot · 2026-01-18T13:01:09Z

r? @fee1-dead

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BoxyUwU · 2026-01-18T16:58:38Z

r? BoxyUwU

compiler/rustc_middle/src/ty/print/pretty.rs

tests/mir-opt/dump_mir_const_generics.rs

BoxyUwU · 2026-01-19T10:46:48Z

@rustbot author

rustbot · 2026-01-19T10:46:53Z

Reminder, once the PR becomes ready for a review, use @rustbot ready.

Human9000-bit · 2026-01-21T09:01:24Z

@rustbot ready

Human9000-bit · 2026-01-21T12:01:23Z

Alright, try_to_raw_bytes seems working now, at least none of examples ICEs.

BoxyUwU · 2026-01-21T12:44:09Z

I think you didn't push your local changes ^^

Human9000-bit · 2026-01-21T13:22:53Z

That's right, because I am confused abt test's error message:

stderr

[ui] tests/ui/const-generics/mgca/wrong_type_const_arr_diag.rs ... F

failures:

---- [ui] tests/ui/const-generics/mgca/wrong_type_const_arr_diag.rs stdout ----
Saved the actual stderr to /home/human9000/contributions/rust/build/x86_64-unknown-linux-gnu/test/ui/const-generics/mgca/wrong_type_const_arr_diag/wrong_type_const_arr_diag.stderr
normalized stderr:
error[E0308]: mismatched types
--> $DIR/wrong_type_const_arr_diag.rs:7:32
|
LL | let _: TakesArr<{ [N] }> = TakesArr::<{ [1] }>;
| ----------------- ^^^^^^^^^^^^^^^^^^^ expected [N], found *b"\x01"
| |
| expected due to this
|
= note: expected struct TakesArr<[N]>
found struct TakesArr<*b"\x01">

error: aborting due to 1 previous error

For more information about this error, try rustc --explain E0308.

note: expected struct TakesArr<[N]>

found struct TakesArr<*b"\x01">

Is that expected error message?

tests/ui/const-generics/mgca/wrong_type_const_arr_diag.rs

Human9000-bit · 2026-01-21T17:14:16Z

that's fine, just had to re-bless tests

Human9000-bit · 2026-01-22T02:59:46Z

@BoxyUwU , I guess we are ready to merge

BoxyUwU · 2026-01-22T09:41:31Z

can you squash your commits

Human9000-bit · 2026-01-22T10:07:34Z

✔️

BoxyUwU · 2026-01-22T11:39:21Z

@bors r+ rollup

rust-bors · 2026-01-22T11:39:24Z

📌 Commit ff97a6a has been approved by BoxyUwU

It is now in the queue for this repository.

@ghost

…uwer Rollup of 11 pull requests Successful merges: - #151001 (rustdoc: render doc(hidden) as a code attribute) - #151042 (fix fallback impl for select_unpredictable intrinsic) - #151220 (option: Use Option::map in Option::cloned) - #151260 (Handle unevaluated ConstKind in in_operand) - #151296 (MGCA: Fix incorrect pretty printing of valtree arrays) - #151423 (Move assert_matches to planned stable path) - #151441 (Fix ICE: Don't try to evaluate type_consts when eagerly collecting items) - #151465 (codegen: clarify some variable names around function calls) - #151468 (fix `f16` doctest FIXMEs) - #151469 (llvm: Tolerate dead_on_return attribute changes) - #151476 (Avoid `-> ()` in derived functions.) r? @ghost

@ghost

…uwer Rollup of 11 pull requests Successful merges: - #151001 (rustdoc: render doc(hidden) as a code attribute) - #151042 (fix fallback impl for select_unpredictable intrinsic) - #151220 (option: Use Option::map in Option::cloned) - #151260 (Handle unevaluated ConstKind in in_operand) - #151296 (MGCA: Fix incorrect pretty printing of valtree arrays) - #151423 (Move assert_matches to planned stable path) - #151441 (Fix ICE: Don't try to evaluate type_consts when eagerly collecting items) - #151465 (codegen: clarify some variable names around function calls) - #151468 (fix `f16` doctest FIXMEs) - #151469 (llvm: Tolerate dead_on_return attribute changes) - #151476 (Avoid `-> ()` in derived functions.) r? @ghost

@ghost

…uwer Rollup of 11 pull requests Successful merges: - #151001 (rustdoc: render doc(hidden) as a code attribute) - #151042 (fix fallback impl for select_unpredictable intrinsic) - #151220 (option: Use Option::map in Option::cloned) - #151260 (Handle unevaluated ConstKind in in_operand) - #151296 (MGCA: Fix incorrect pretty printing of valtree arrays) - #151423 (Move assert_matches to planned stable path) - #151441 (Fix ICE: Don't try to evaluate type_consts when eagerly collecting items) - #151465 (codegen: clarify some variable names around function calls) - #151468 (fix `f16` doctest FIXMEs) - #151469 (llvm: Tolerate dead_on_return attribute changes) - #151476 (Avoid `-> ()` in derived functions.) r? @ghost

Rollup merge of #151296 - Human9000-bit:const-array-mir-dump-fix, r=BoxyUwU MGCA: Fix incorrect pretty printing of valtree arrays Fixes #151126 - **add failing test** - **fix: additional check whether const array could be printed as raw bytes** As I figured out, the problem was in `pretty_print_const_valtree`, where it tried to print unevaluated consts as if they were evaluated, which resulted in ICE.

@ghost

…uwer Rollup of 11 pull requests Successful merges: - rust-lang/rust#151001 (rustdoc: render doc(hidden) as a code attribute) - rust-lang/rust#151042 (fix fallback impl for select_unpredictable intrinsic) - rust-lang/rust#151220 (option: Use Option::map in Option::cloned) - rust-lang/rust#151260 (Handle unevaluated ConstKind in in_operand) - rust-lang/rust#151296 (MGCA: Fix incorrect pretty printing of valtree arrays) - rust-lang/rust#151423 (Move assert_matches to planned stable path) - rust-lang/rust#151441 (Fix ICE: Don't try to evaluate type_consts when eagerly collecting items) - rust-lang/rust#151465 (codegen: clarify some variable names around function calls) - rust-lang/rust#151468 (fix `f16` doctest FIXMEs) - rust-lang/rust#151469 (llvm: Tolerate dead_on_return attribute changes) - rust-lang/rust#151476 (Avoid `-> ()` in derived functions.) r? @ghost

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Human9000-bit force-pushed the const-array-mir-dump-fix branch from 054805e to f0205aa Compare January 21, 2026 17:13

BoxyUwU approved these changes Jan 22, 2026

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fix: allow to print const array as raw bytes only if possible to do so

ff97a6a

Human9000-bit force-pushed the const-array-mir-dump-fix branch from f0205aa to ff97a6a Compare January 22, 2026 10:07

rust-bors bot added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jan 22, 2026

BoxyUwU changed the title ~~MGCA: Fix incorrect MIR const array printing~~ MGCA: Fix incorrect pretty printing of valtree arrays Jan 22, 2026

JonathanBrouwer mentioned this pull request Jan 22, 2026

Rollup of 11 pull requests #151490

Merged

rust-bors bot merged commit 96a40e9 into rust-lang:main Jan 22, 2026
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rustbot added this to the 1.95.0 milestone Jan 22, 2026

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MGCA: Fix incorrect pretty printing of valtree arrays #151296

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