gccrs: Implement rest pattern support for slice patterns #4062
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powerboat9
approved these changes
Aug 11, 2025
This patch adds support for compiling rest patterns present in slice patterns
(e.g. `[1, .., 2]`). 006t.original output from compiling match-slicepattern-slice-2.rs
for first 2 match arms:
...
if (RUSTTMP.3.len > 1 && *NON_LVALUE_EXPR <RUSTTMP.3.data> == 1)
{
{
struct () RUSTTMP.4;
{
struct () RUSTTMP.5;
{
..
}
}
goto <D.139>;
}
}
if ((RUSTTMP.3.len > 1 && *NON_LVALUE_EXPR <RUSTTMP.3.data> == 0) && *(RUSTTMP.3.data + (sizetype) (RUSTTMP.3.len + 18446744073709551615) * 4) == 0)
{
{
struct () RUSTTMP.6;
{
struct () RUSTTMP.7;
{
}
}
goto <D.139>;
}
}
...
gcc/rust/ChangeLog:
* hir/tree/rust-hir-pattern.h: Add SlicePatternItems base class and
SlicePatternItemsNoRest/SlicePatternItemsHasRest derived classes.
Update SlicePattern to hold patterns using the new classes.
* hir/tree/rust-hir-full-decls.h: Declare new classes.
* hir/tree/rust-hir.cc: Add visits for new classes.
* hir/tree/rust-hir-visitor.h: Add visits for new classes.
* hir/tree/rust-hir-visitor.cc: Implement visits for new classes.
* hir/rust-hir-dump.h: Add visits for new classes.
* hir/rust-hir-dump.cc: Implement Dump::visit for new classes.
* hir/rust-ast-lower-base.h: Declare new lower_slice_pattern_no_rest/has_rest
methods.
* hir/rust-ast-lower-base.cc: Implement lower_slice_pattern_no_rest/has_rest
to lower AST slice pattern items to HIR.
* hir/rust-ast-lower-pattern.cc: Update ASTLoweringPattern::visit for
SlicePattern to use new lowering methods.
* backend/rust-compile-pattern.cc: Update CompilePatternCheckExpr::visit
and CompilePatternBindings::visit for SlicePattern to handle
SlicePatternItemsNoRest/HasRest.
* checks/errors/borrowck/rust-bir-builder-pattern.cc: Update
PatternBindingBuilder::visit for SlicePattern to iterate members correctly.
* checks/errors/borrowck/rust-bir-builder-struct.h: Add visits for new
classes.
* checks/errors/borrowck/rust-function-collector.h: Add visits for new
classes.
* checks/errors/rust-const-checker.h: Add visits for new classes.
* checks/errors/rust-const-checker.cc: Implement empty visits for new classes.
* checks/errors/rust-hir-pattern-analysis.h: Add visits for new classes.
* checks/errors/rust-hir-pattern-analysis.cc: Implement empty visits for new
classes.
* checks/errors/rust-unsafe-checker.h: Add visits for new classes.
* checks/errors/rust-unsafe-checker.cc: Implement empty visits for new
classes.
* typecheck/rust-hir-type-check-pattern.cc: Update TypeCheckPattern::visit
for SlicePattern to handle SlicePatternItemsNoRest/HasRest.
gcc/testsuite/ChangeLog:
* rust/compile/slice_rest_pattern.rs: Removed -fsyntax-only.
Signed-off-by: Yap Zhi Heng <[email protected]>
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My meatiest PR to this repo so far. I'm ready to be grilled for my code style (especially in
rust-compile-pattern.cc).Similar to my changes made to the AST for rest-pattern-in-slice-pattern support, the main change is adding
SlicePatternItemsNoRestandSlicePatternItemsHasRestclasses which hold patterns forHIR::SlicePattern. The changes made torust-compile-pattern.ccis also quite significant due to having 4 different cases to handle (array parent + no rest, array parent + has rest, slice parent + no rest, slice parent + has rest) - reviewers should focus more on that file, since other changes are mainly cascading changes stemmed from the introduction of new classes.