AstGen: lower anon struct inits differently

This is a companion commit to f2a5d0bf94897554e25e889dc1c6c4c7fc6c1217.
What that one did for tuples, this one does for anonymous structs.

src/AstGen.zig

@@ -1352,6 +1352,7 @@ fn arrayInitExpr(
             if (types.array == .none) {
                 // We treat this case differently so that we don't get a crash when
                 // analyzing array_base_ptr against an alloc_inferred_mut.
+                // See corresponding logic in structInitExpr.
                 const result = try arrayInitExprRlNone(gz, scope, node, array_init.ast.elements, .array_init_anon);
                 return rvalue(gz, rl, result, node);
             } else {
@@ -1591,7 +1592,18 @@ fn structInitExpr(
             const result = try structInitExprRlTy(gz, scope, node, struct_init, inner_ty_inst, .struct_init);
             return rvalue(gz, rl, result, node);
         },
-        .ptr, .inferred_ptr => |ptr_inst| return structInitExprRlPtr(gz, scope, rl, node, struct_init, ptr_inst),
+        .ptr => |ptr_inst| return structInitExprRlPtr(gz, scope, rl, node, struct_init, ptr_inst),
+        .inferred_ptr => |ptr_inst| {
+            if (struct_init.ast.type_expr == 0) {
+                // We treat this case differently so that we don't get a crash when
+                // analyzing field_base_ptr against an alloc_inferred_mut.
+                // See corresponding logic in arrayInitExpr.
+                const result = try structInitExprRlNone(gz, scope, node, struct_init, .struct_init_anon);
+                return rvalue(gz, rl, result, node);
+            } else {
+                return structInitExprRlPtr(gz, scope, rl, node, struct_init, ptr_inst);
+            }
+        },
         .block_ptr => |block_gz| return structInitExprRlPtr(gz, scope, rl, node, struct_init, block_gz.rl_ptr),
     }
 }

test/behavior/tuple.zig

@@ -110,8 +110,6 @@ test "pass tuple to comptime var parameter" {
 }
 
 test "tuple initializer for var" {
-    if (builtin.zig_backend != .stage1) return error.SkipZigTest; // TODO
-
     const S = struct {
         fn doTheTest() void {
             const Bytes = struct {