I try to reduce the code of <a class="issue-link js-issue-link" data-error-text="Fail

Because this hack, I think. <div class

program A set tainted_by_errors to <code class="notra

ICE: Unexpected type for constructor `Variant(1)` about rust HOT 3 OPEN

Luv-Ray commented on August 24, 2024

ICE: Unexpected type for constructor `Variant(1)`

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Comments (3)

Luv-Ray commented on August 24, 2024

My thought after some debug:
There are some ways to trigger panic in compiler/rustc_pattern_analysis, because we trust that the type analysed here are all correct but they may not.

Consider two programs below:

// program A
enum NestedEnum {
    First,
    Second,
}

enum Enum {
    Variant(*const ()),
    // Variant(*const &'a ()),
}

fn foo(x: Enum) {
    match x {
        Enum::Variant(NestedEnum::Second) => {}
    }
}

// program B
enum NestedEnum {
    First,
    Second,
}

enum Enum {
    // Variant(*const ()),
    Variant(*const &'a ()),
}

fn foo(x: Enum) {
    match x {
        Enum::Variant(NestedEnum::Second) => {}
    }
}

program B will panic at compile while program A not. The difference occurs here:

rust/compiler/rustc_mir_build/src/thir/pattern/check_match.rs

Lines 29 to 32 in 6a207f4

 pub(crate) fn check_match(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Result<(), ErrorGuaranteed> { 

 let typeck_results = tcx.typeck(def_id); 

 let (thir, expr) = tcx.thir_body(def_id)?; 

 let thir = thir.borrow();

program A will early return at tcx.thir_body(def_id)?, but program B will not and cause the panic.
I have checked the typeck_results of two programs, and there is a key different between them: in program A typeck_results.tainted_by_errors is Some(ErrorGuaranteed(())), and in program B that is None.

TypeckResults { hir_owner: DefId(0:12 ~ tmp[d0fa]::foo), type_dependent_defs: UnordMap { inner: {} }, field_indices: UnordMap { inner: {} }, nested_fields: UnordMap { inner: {} }, node_types: UnordMap { inner: {16: (), 13: (), 10: NestedEnum, 4: Enum, 1: Enum, 14: (), 11: Enum, 2: Enum, 15: (), 3: ()} }, node_args: UnordMap { inner: {} }, user_provided_types: UnordMap { inner: {} }, user_provided_sigs: UnordMap { inner: {} }, adjustments: UnordMap { inner: {} }, pat_binding_modes: UnordMap { inner: {2: BindingMode(No, Not)} }, rust_2024_migration_desugared_pats: UnordSet { inner: {} }, pat_adjustments: UnordMap { inner: {} }, skipped_ref_pats: UnordSet { inner: {} }, closure_kind_origins: UnordMap { inner: {} }, liberated_fn_sigs: UnordMap { inner: {0: fn(Enum)} }, fru_field_types: UnordMap { inner: {} }, coercion_casts: UnordSet { inner: {} }, used_trait_imports: UnordSet { inner: {} }, tainted_by_errors: Some(ErrorGuaranteed(())), concrete_opaque_types: {}, closure_min_captures: UnordMap { inner: {} }, closure_fake_reads: UnordMap { inner: {} }, rvalue_scopes: RvalueScopes { map: UnordMap { inner: {} } }, coroutine_stalled_predicates: {}, treat_byte_string_as_slice: UnordSet { inner: {} }, closure_size_eval: UnordMap { inner: {} }, offset_of_data: UnordMap { inner: {} }, inline_consts: {} }

TypeckResults { hir_owner: DefId(0:12 ~ tmp2[62c9]::foo), type_dependent_defs: UnordMap { inner: {} }, field_indices: UnordMap { inner: {} }, nested_fields: UnordMap { inner: {} }, node_types: UnordMap { inner: {16: (), 13: (), 10: NestedEnum, 4: Enum, 1: Enum, 14: (), 11: Enum, 2: Enum, 15: (), 3: ()} }, node_args: UnordMap { inner: {} }, user_provided_types: UnordMap { inner: {} }, user_provided_sigs: UnordMap { inner: {} }, adjustments: UnordMap { inner: {} }, pat_binding_modes: UnordMap { inner: {2: BindingMode(No, Not)} }, rust_2024_migration_desugared_pats: UnordSet { inner: {} }, pat_adjustments: UnordMap { inner: {} }, skipped_ref_pats: UnordSet { inner: {} }, closure_kind_origins: UnordMap { inner: {} }, liberated_fn_sigs: UnordMap { inner: {0: fn(Enum)} }, fru_field_types: UnordMap { inner: {} }, coercion_casts: UnordSet { inner: {} }, used_trait_imports: UnordSet { inner: {} }, tainted_by_errors: None, concrete_opaque_types: {}, closure_min_captures: UnordMap { inner: {} }, closure_fake_reads: UnordMap { inner: {} }, rvalue_scopes: RvalueScopes { map: UnordMap { inner: {} } }, coroutine_stalled_predicates: {}, treat_byte_string_as_slice: UnordSet { inner: {} }, closure_size_eval: UnordMap { inner: {} }, offset_of_data: UnordMap { inner: {} }, inline_consts: {} }

In TyCtxt::thir_body's comment, it says: If typeck for that body failed, returns an empty Thir., but seems that it return ErrorGuaranteed rather than empty Thir if typeck failed. Is the description wrong here?

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Luv-Ray commented on August 24, 2024

Because this hack, I think.

rust/compiler/rustc_hir_typeck/src/writeback.rs

Lines 125 to 130 in 76c7382

 // HACK: We specifically don't want the (opaque) error from tainting our 

 // inference context. That'll prevent us from doing opaque type inference 

 // later on in borrowck, which affects diagnostic spans pretty negatively. 

 if let Some(e) = fcx.tainted_by_errors() { 

 wbcx.typeck_results.tainted_by_errors = Some(e); 

 }

from rust.

Luv-Ray commented on August 24, 2024

program A set tainted_by_errors to Some(ErrorGuaranteed(())) here, but program B not.

rust/compiler/rustc_hir_typeck/src/pat.rs

Line 1165 in 921645c

e.emit();

from rust.

ICE: Unexpected type for constructor `Variant(1)` about rust HOT 3 OPEN

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	pub(crate) fn check_match(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Result<(), ErrorGuaranteed> {
	let typeck_results = tcx.typeck(def_id);
	let (thir, expr) = tcx.thir_body(def_id)?;
	let thir = thir.borrow();

	// HACK: We specifically don't want the (opaque) error from tainting our
	// inference context. That'll prevent us from doing opaque type inference
	// later on in borrowck, which affects diagnostic spans pretty negatively.
	if let Some(e) = fcx.tainted_by_errors() {
	wbcx.typeck_results.tainted_by_errors = Some(e);
	}