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Stricter type pattern matching rules #463

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Merged
merged 1 commit into from
Feb 26, 2025
Merged

Stricter type pattern matching rules #463

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17 changes: 16 additions & 1 deletion src/org/jetbrains/java/decompiler/modules/decompiler/SwitchPatternMatchProcessor.java
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Original file line number Diff line number Diff line change
Expand Up @@ -187,7 +187,7 @@ private static boolean processStatement(SwitchStatement stat, Statement root) {
if (assign.getLeft() instanceof VarExprent) {
VarExprent var = (VarExprent) assign.getLeft();

if (assign.getRight() instanceof FunctionExprent && ((FunctionExprent) assign.getRight()).getFuncType() == FunctionExprent.FunctionType.CAST) {
if (isPatternMatchingCastAssignment(head, assign)) {
FunctionExprent cast = (FunctionExprent) assign.getRight();

List<Exprent> operands = new ArrayList<>();
Expand Down Expand Up @@ -547,4 +547,19 @@ private static boolean isSwitchPatternMatch(SwitchHeadExprent head) {
public static boolean hasPatternMatch(RootStatement root) {
return root.mt.getBytecodeVersion().hasSwitchPatternMatch() && DecompilerContext.getOption(IFernflowerPreferences.PATTERN_MATCHING);
}

private static boolean isPatternMatchingCastAssignment(final SwitchHeadExprent switchHead, final AssignmentExprent assignment) {
if (!(assignment.getRight() instanceof final FunctionExprent functionExprent)) return false;
if (functionExprent.getFuncType() != FunctionType.CAST) return false;

final List<Exprent> lstOperands = functionExprent.getLstOperands();
// We expect the assignment to be a literal `n = (Type) m`.
// Any other operands are not allowed in simple pattern matching.
if (lstOperands.size() < 2) return false;
if (!(lstOperands.get(0) instanceof final VarExprent switchHeadRef)) return false;
if (!(lstOperands.get(1) instanceof final ConstExprent castTypeRef)) return false;
if (!switchHead.containsVar(switchHeadRef.getVarVersionPair())) return false; // Not the switch head var ref

return true;
}
}
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