compiler: fix: the --opt-zcopy and --opt-zappend optimizations may ca…

…use compile issues

src/julec/opt/expr.jule

@@ -874,6 +874,13 @@ impl exprOptimizer {
 		// Optimization of the dest argument belongs to the back-end.
 		if IsZCopyArray(m.Src.Model) {
 			mut ie := (&sema::SlicingExpr)(m.Src.Model)
+
+			// Special case: already optimized.
+			_, ok := (&ArrayAsSlice)(unsafe { *(*any)(&ie.Expr.Model) })
+			if ok {
+				ret
+			}
+
 			mut model := any(&ArrayAsSlice{
 				Expr: ie.Expr.Model,
 			})
@@ -887,6 +894,13 @@ impl exprOptimizer {
 		}
 		if IsZAppendArray(m.Elements.Model) {
 			mut ie := (&sema::SlicingExpr)(m.Elements.Model)
+
+			// Special case: already optimized.
+			_, ok := (&ArrayAsSlice)(unsafe { *(*any)(&ie.Expr.Model) })
+			if ok {
+				ret
+			}
+
 			mut model := any(&ArrayAsSlice{
 				Expr: ie.Expr.Model,
 			})