mGCA: Validate const literal against expected type#152001
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reddevilmidzy wants to merge 1 commit intorust-lang:mainfrom
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mGCA: Validate const literal against expected type#152001reddevilmidzy wants to merge 1 commit intorust-lang:mainfrom
reddevilmidzy wants to merge 1 commit intorust-lang:mainfrom
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| tcx.at(span).lit_to_const(input) | ||
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| fn const_lit_matches_ty(&self, kind: &LitKind, ty: Ty<'tcx>, neg: bool) -> bool { |
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I think in most cases we actually don't want to emit errors during HIR ty lowering for type mismatches here. E.g. if we have a true literal it doesn't really matter if the expected type is u32, we can still lower to a 0x1 valtree of type bool and then get a type checking error later.
Separately from this, we already do these checks in fn lit_to_const (just ICEing if they don't hold instead of a proper error) so it probably doesn't make sense to duplicate them here too 🤔
I think it would make sense for lit_to_const to return an Option<ty::Value<'tcx>> and stop ICEing/erroring altogether.
You could then:
- Move
const_lit_matches_tyto THIR building for patterns (the only place other than const-generics that callslit_to_const) and create aty::ConstKind::Errorif it'sfalse(or iflit_to_constreturnsNone) - Here in HIR ty lowering we can emit a proper error about needing more type information for the literal if
lit_to_constreturnsNone. And we can entirely ignore the possibility of type mismatches because type checking should take care of that for us
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very cool :) thanks for working on this |
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☔ The latest upstream changes (presumably #152213) made this pull request unmergeable. Please resolve the merge conflicts. |
This was referenced Feb 6, 2026
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…=oli-obk Dont strip const blocks in array lengths r? oli-obk mGCA now handles const blocks by *always* handling them during `lower_expr_to_const_arg_direct` instead of *sometimes* stripping them out at parse time. This is just generally a lot clearer/nicer but also means parsing isn't lossy which is just straight up wrong. We now use `MgcaDisambiguation::Direct` for const blocks because we "directly" represent a const block as `hir::ConstArgKind::Anon` :> The only time that an anon const for const generics uses `MgcaDisambiguation::AnonConst` is for unbraced literals. Once we properly support literals in `hir::ConstArgKind` (see rust-lang#152139 rust-lang#152001) then `MgcaDisambiguation` can be renamed to `AnonConstKind` with `TypeSystem` and `NonTypeSystem` variants. We can also get rid of `mgca_direct_lit_hack`. I expect this to be a very nice cleanup :) Fixes rust-lang/rustfmt#6788 The diff relating to passing spans around is to avoid a bunch of mGCA diagnostics changing from `const {}` to `{}`. I'm not entirely sure why this was happening. cc @rust-lang/rustfmt How do I run the tests in the rustfmt repo from here? `x test rustfmt` only seems to run like 100 tests and doesn't result in a `target/issue-6788.rs` getting created. I've verified locally that this formats correctly though
JonathanBrouwer
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…=oli-obk Dont strip const blocks in array lengths r? oli-obk mGCA now handles const blocks by *always* handling them during `lower_expr_to_const_arg_direct` instead of *sometimes* stripping them out at parse time. This is just generally a lot clearer/nicer but also means parsing isn't lossy which is just straight up wrong. We now use `MgcaDisambiguation::Direct` for const blocks because we "directly" represent a const block as `hir::ConstArgKind::Anon` :> The only time that an anon const for const generics uses `MgcaDisambiguation::AnonConst` is for unbraced literals. Once we properly support literals in `hir::ConstArgKind` (see rust-lang#152139 rust-lang#152001) then `MgcaDisambiguation` can be renamed to `AnonConstKind` with `TypeSystem` and `NonTypeSystem` variants. We can also get rid of `mgca_direct_lit_hack`. I expect this to be a very nice cleanup :) Fixes rust-lang/rustfmt#6788 The diff relating to passing spans around is to avoid a bunch of mGCA diagnostics changing from `const {}` to `{}`. I'm not entirely sure why this was happening. cc @rust-lang/rustfmt How do I run the tests in the rustfmt repo from here? `x test rustfmt` only seems to run like 100 tests and doesn't result in a `target/issue-6788.rs` getting created. I've verified locally that this formats correctly though
JonathanBrouwer
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Feb 6, 2026
…=oli-obk Dont strip const blocks in array lengths r? oli-obk mGCA now handles const blocks by *always* handling them during `lower_expr_to_const_arg_direct` instead of *sometimes* stripping them out at parse time. This is just generally a lot clearer/nicer but also means parsing isn't lossy which is just straight up wrong. We now use `MgcaDisambiguation::Direct` for const blocks because we "directly" represent a const block as `hir::ConstArgKind::Anon` :> The only time that an anon const for const generics uses `MgcaDisambiguation::AnonConst` is for unbraced literals. Once we properly support literals in `hir::ConstArgKind` (see rust-lang#152139 rust-lang#152001) then `MgcaDisambiguation` can be renamed to `AnonConstKind` with `TypeSystem` and `NonTypeSystem` variants. We can also get rid of `mgca_direct_lit_hack`. I expect this to be a very nice cleanup :) Fixes rust-lang/rustfmt#6788 The diff relating to passing spans around is to avoid a bunch of mGCA diagnostics changing from `const {}` to `{}`. I'm not entirely sure why this was happening. cc @rust-lang/rustfmt How do I run the tests in the rustfmt repo from here? `x test rustfmt` only seems to run like 100 tests and doesn't result in a `target/issue-6788.rs` getting created. I've verified locally that this formats correctly though
JonathanBrouwer
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Feb 7, 2026
…=oli-obk Dont strip const blocks in array lengths r? oli-obk mGCA now handles const blocks by *always* handling them during `lower_expr_to_const_arg_direct` instead of *sometimes* stripping them out at parse time. This is just generally a lot clearer/nicer but also means parsing isn't lossy which is just straight up wrong. We now use `MgcaDisambiguation::Direct` for const blocks because we "directly" represent a const block as `hir::ConstArgKind::Anon` :> The only time that an anon const for const generics uses `MgcaDisambiguation::AnonConst` is for unbraced literals. Once we properly support literals in `hir::ConstArgKind` (see rust-lang#152139 rust-lang#152001) then `MgcaDisambiguation` can be renamed to `AnonConstKind` with `TypeSystem` and `NonTypeSystem` variants. We can also get rid of `mgca_direct_lit_hack`. I expect this to be a very nice cleanup :) Fixes rust-lang/rustfmt#6788 The diff relating to passing spans around is to avoid a bunch of mGCA diagnostics changing from `const {}` to `{}`. I'm not entirely sure why this was happening. cc @rust-lang/rustfmt How do I run the tests in the rustfmt repo from here? `x test rustfmt` only seems to run like 100 tests and doesn't result in a `target/issue-6788.rs` getting created. I've verified locally that this formats correctly though
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Rollup merge of #152234 - BoxyUwU:dont_strip_const_blocks, r=oli-obk Dont strip const blocks in array lengths r? oli-obk mGCA now handles const blocks by *always* handling them during `lower_expr_to_const_arg_direct` instead of *sometimes* stripping them out at parse time. This is just generally a lot clearer/nicer but also means parsing isn't lossy which is just straight up wrong. We now use `MgcaDisambiguation::Direct` for const blocks because we "directly" represent a const block as `hir::ConstArgKind::Anon` :> The only time that an anon const for const generics uses `MgcaDisambiguation::AnonConst` is for unbraced literals. Once we properly support literals in `hir::ConstArgKind` (see #152139 #152001) then `MgcaDisambiguation` can be renamed to `AnonConstKind` with `TypeSystem` and `NonTypeSystem` variants. We can also get rid of `mgca_direct_lit_hack`. I expect this to be a very nice cleanup :) Fixes rust-lang/rustfmt#6788 The diff relating to passing spans around is to avoid a bunch of mGCA diagnostics changing from `const {}` to `{}`. I'm not entirely sure why this was happening. cc @rust-lang/rustfmt How do I run the tests in the rustfmt repo from here? `x test rustfmt` only seems to run like 100 tests and doesn't result in a `target/issue-6788.rs` getting created. I've verified locally that this formats correctly though
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close: #151625
close: #150983