Destructuring array matcher should not match string codepoints

docs/content/manual/manual.yml

@@ -2983,6 +2983,10 @@ sections:
           value at the index for an array pattern element, `null` is
           bound to that variable.
 
+          Note that array patterns do not match strings.  That is, `.
+          as [$x]` will not match the first codepoint in `.` if `.` is
+          a string.
+
           Variables are scoped over the rest of the expression that defines
           them, so
 
@@ -3059,6 +3063,9 @@ sections:
           - program: '.[] as [$a] ?// [$b] | if $a != null then error("err: \($a)") else {$a,$b} end'
             input: '[[3]]'
             output: ['{"a":null,"b":3}']
+          - program: '. as [$x] ?// $x | $x'
+            input: '"abc"'
+            output: ['"abc"']
 
       - title: 'Defining Functions'
         body: |

src/compile.c

@@ -995,7 +995,7 @@ block gen_array_matcher(block left, block curr) {
 
   // `left` goes at the end so that the const index is in a predictable place
   return BLOCK(gen_op_simple(DUP), gen_subexp(gen_const(jv_number(index))),
-               gen_op_simple(INDEX), curr, left);
+               gen_op_simple(INDEX_D), curr, left);
 }
 
 block gen_object_matcher(block name, block curr) {

src/execute.c

@@ -674,11 +674,12 @@ jv jq_next(jq_state *jq) {
     }
 
     case INDEX:
+    case INDEX_D:
     case INDEX_OPT: {
       jv t = stack_pop(jq);
       jv k = stack_pop(jq);
       jv v;
-      if (jv_get_kind(t) == JV_KIND_STRING && jv_get_kind(k) == JV_KIND_NUMBER) {
+      if (opcode != INDEX_D && jv_get_kind(t) == JV_KIND_STRING && jv_get_kind(k) == JV_KIND_NUMBER) {
         switch (jv_get_string_kind(t)) {
         case JV_STRING_KIND_UTF8:
           uint32_t c = jv_string_index(t, jv_number_value(k));
@@ -730,7 +731,7 @@ jv jq_next(jq_state *jq) {
         stack_push(jq, v);
       } else {
         jv_free(k);
-        if (opcode == INDEX)
+        if (opcode == INDEX || opcode == INDEX_D)
           set_error(jq, v);
         else
           jv_free(v);

src/opcode_list.h

@@ -10,6 +10,7 @@ OP(STOREV, VARIABLE, 1, 0)
 OP(STORE_GLOBAL, GLOBAL, 0, 0)
 OP(INDEX, NONE,     2, 1)
 OP(INDEX_OPT, NONE,     2, 1)
+OP(INDEX_D, NONE,     2, 1)   /* For gen_array_matcher() -- destructuring */
 OP(EACH,  NONE,     1, 1)
 OP(EACH_OPT,  NONE, 1, 1)
 OP(FORK,  BRANCH,   0, 0)