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Rollup merge of #68314 - oli-obk:true_unwind, r=eddyb

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Stop treating `FalseEdges` and `FalseUnwind` as having semantic value for const eval

This change does not expose loops or conditions to stable const fns because we check those at the HIR level and in the regular const validity checks.

cc @ecstatic-morse

r? @eddyb
This commit is contained in:
Tyler Mandry 2020-01-17 17:28:22 -08:00 • committed by GitHub
commit dd6a83875e
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GPG key ID: 4AEE18F83AFDEB23
1 changed files with 6 additions and 13 deletions
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19
src/librustc_mir/transform/qualify_min_const_fn.rs
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@ -309,7 +309,11 @@ fn check_terminator(
) -> McfResult {
let span = terminator.source_info.span;
match &terminator.kind {
TerminatorKind::Goto { .. } | TerminatorKind::Return | TerminatorKind::Resume => Ok(()),
TerminatorKind::FalseEdges { .. }
| TerminatorKind::FalseUnwind { .. }
| TerminatorKind::Goto { .. }
| TerminatorKind::Return
| TerminatorKind::Resume => Ok(()),
TerminatorKind::Drop { location, .. } => check_place(tcx, location, span, def_id, body),
TerminatorKind::DropAndReplace { location, value, .. } => {
@ -317,13 +321,10 @@ fn check_terminator(
check_operand(tcx, value, span, def_id, body)
}
TerminatorKind::FalseEdges { .. } | TerminatorKind::SwitchInt { .. }
if !feature_allowed(tcx, def_id, sym::const_if_match) =>
{
TerminatorKind::SwitchInt { .. } if !feature_allowed(tcx, def_id, sym::const_if_match) => {
Err((span, "loops and conditional expressions are not stable in const fn".into()))
}
TerminatorKind::FalseEdges { .. } => Ok(()),
TerminatorKind::SwitchInt { discr, switch_ty: _, values: _, targets: _ } => {
check_operand(tcx, discr, span, def_id, body)
}
@ -367,13 +368,5 @@ fn check_terminator(
TerminatorKind::Assert { cond, expected: _, msg: _, target: _, cleanup: _ } => {
check_operand(tcx, cond, span, def_id, body)
}
TerminatorKind::FalseUnwind { .. } if feature_allowed(tcx, def_id, sym::const_loop) => {
Ok(())
}
TerminatorKind::FalseUnwind { .. } => {
Err((span, "loops are not allowed in const fn".into()))
}
}
}