stage2: concat/mult of slices should yield slice

Author: topolarity

src/Sema.zig

@@ -8499,6 +8499,7 @@ fn zirArrayCat(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError!Ai
     const tracy = trace(@src());
     defer tracy.end();
 
+    const target = sema.mod.getTarget();
     const inst_data = sema.code.instructions.items(.data)[inst].pl_node;
     const extra = sema.code.extraData(Zir.Inst.Bin, inst_data.payload_index).data;
     const lhs = sema.resolveInst(extra.lhs);
@@ -8573,6 +8574,16 @@ fn zirArrayCat(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError!Ai
             const decl = try anon_decl.finish(ty, val, 0);
             if (lhs_single_ptr or rhs_single_ptr) {
                 return sema.analyzeDeclRef(decl);
+            } else if (lhs_ty.isSlice() or rhs_ty.isSlice()) {
+                const slice_ty = try Type.ptr(sema.arena, target, .{
+                    .pointee_type = decl.ty.childType(),
+                    .sentinel = decl.ty.sentinel(),
+                    .@"addrspace" = .generic,
+                    .mutable = false,
+                    .size = .Slice,
+                });
+                const ptr_to_array = try sema.analyzeDeclRef(decl);
+                return sema.coerceArrayPtrToSlice(block, slice_ty, ptr_to_array, .unneeded);
             } else {
                 return sema.analyzeDeclVal(block, .unneeded, decl);
             }
@@ -8677,6 +8688,7 @@ fn zirArrayMul(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError!Ai
     const tracy = trace(@src());
     defer tracy.end();
 
+    const target = sema.mod.getTarget();
     const inst_data = sema.code.instructions.items(.data)[inst].pl_node;
     const extra = sema.code.extraData(Zir.Inst.Bin, inst_data.payload_index).data;
     const lhs = sema.resolveInst(extra.lhs);
@@ -8746,6 +8758,16 @@ fn zirArrayMul(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError!Ai
         const decl = try anon_decl.finish(final_ty, val, 0);
         if (is_single_ptr) {
             return sema.analyzeDeclRef(decl);
+        } else if (lhs_ty.isSlice()) {
+            const slice_ty = try Type.ptr(sema.arena, target, .{
+                .pointee_type = decl.ty.childType(),
+                .sentinel = decl.ty.sentinel(),
+                .@"addrspace" = .generic,
+                .mutable = false,
+                .size = .Slice,
+            });
+            const ptr_to_array = try sema.analyzeDeclRef(decl);
+            return sema.coerceArrayPtrToSlice(block, slice_ty, ptr_to_array, .unneeded);
         } else {
             return sema.analyzeDeclVal(block, .unneeded, decl);
         }

test/behavior/slice.zig

@@ -584,8 +584,6 @@ test "type coercion of pointer to anon struct literal to pointer to slice" {
 }
 
 test "array concat of slices gives slice" {
-    if (builtin.zig_backend != .stage1) return error.SkipZigTest; // TODO
-
     comptime {
         var a: []const u8 = "aoeu";
         var b: []const u8 = "asdf";
@@ -594,6 +592,16 @@ test "array concat of slices gives slice" {
     }
 }
 
+test "array mult of slice gives slice" {
+    if (builtin.zig_backend == .stage1) return error.SkipZigTest; // Stage 1 does not support multiplying slices
+
+    comptime {
+        var a: []const u8 = "aoeu";
+        const c = a ** 2;
+        try expect(std.mem.eql(u8, c, "aoeuaoeu"));
+    }
+}
+
 test "slice bounds in comptime concatenation" {
     if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO