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gccrs: Fix negative bounds in RangePattern being handled incorrectly #4243

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merged 2 commits into from
Oct 31, 2025
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gccrs: Fix negative bounds in RangePattern being handled incorrectly #4243

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gccrs: Fix `RangePattern` negative literal bounds being treated as po…
Polygonalr Oct 26, 2025
8ee2b15
gccrs: Implement E0579 error checking in RangePattern compilation
Polygonalr Oct 20, 2025
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26 changes: 26 additions & 0 deletions gcc/rust/backend/rust-compile-pattern.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -119,6 +119,8 @@ compile_range_pattern_bound (HIR::RangePatternBound &bound,

HIR::LiteralExpr litexpr (mappings, ref.get_literal (), locus,
std::vector<AST::Attribute> ());
if (ref.get_has_minus ())
litexpr.set_negative ();

result = CompileExpr::Compile (litexpr, ctx);
}
Expand Down Expand Up @@ -159,6 +161,30 @@ CompilePatternCheckExpr::visit (HIR::RangePattern &pattern)
pattern.get_mappings (),
pattern.get_locus (), ctx);

rust_assert (
(TREE_CODE (upper) == REAL_CST && TREE_CODE (lower) == REAL_CST)
|| (TREE_CODE (upper) == INTEGER_CST && TREE_CODE (lower) == INTEGER_CST));
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Does 1f32..1.2f32 break anything?

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Triggers an error that shouldn't be triggered lol, maybe we can create a new issue for it.

error: mismatched types, expected ‘f32’ but got ‘<integer>’ [E0308]
    7 |         1f32..1.2f32 => 1,
      |         ^~~~

Anyways, 1.0f32..1.2f32 compiles properly and does not trigger E0579 but -1.2f32..-1.0f32 triggers E0579... not sure what went wrong here :/

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probably something thats doing a unify but should be doing a cast_site which can fall back to a coercion possibly


bool error_E0579 = false;
if (TREE_CODE (upper) == REAL_CST)
{
REAL_VALUE_TYPE upper_r = TREE_REAL_CST (upper);
REAL_VALUE_TYPE lower_r = TREE_REAL_CST (lower);
if (real_compare (GE_EXPR, &lower_r, &upper_r))
error_E0579 = true;
}
else if (TREE_CODE (upper) == INTEGER_CST)
{
auto upper_wi = wi::to_wide (upper).to_shwi ();
auto lower_wi = wi::to_wide (lower).to_shwi ();
if (lower_wi >= upper_wi)
error_E0579 = true;
}

if (error_E0579)
rust_error_at (pattern.get_locus (), ErrorCode::E0579,
"lower range bound must be less than upper");

ComparisonOperator upper_cmp = pattern.is_inclusive_range ()
? ComparisonOperator::LESS_OR_EQUAL
: ComparisonOperator::LESS_THAN;
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10 changes: 10 additions & 0 deletions gcc/testsuite/rust/compile/issue-3659.rs
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@@ -0,0 +1,10 @@
#![feature(exclusive_range_pattern)]

fn main() {
let x = 3;

match x {
0..-1 => 2, // { dg-error "lower range bound must be less than upper .E0579." }
_ => 3,
};
}
10 changes: 10 additions & 0 deletions gcc/testsuite/rust/compile/issue-4242.rs
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@@ -0,0 +1,10 @@
#![feature(exclusive_range_pattern)]

fn main() {
let x = 1;

match x {
-55..0 => 2,
-99..-55 => 3,
};
}
11 changes: 11 additions & 0 deletions gcc/testsuite/rust/execute/torture/issue-4242.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,11 @@
#![feature(exclusive_range_pattern)]

fn main() -> i32 {
let x = -77;

match x {
-55..99 => 1,
-99..-55 => 0, // the correct case
_ => 1,
}
}
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