Fix parsing for vectors of literals.

This was broken in two ways:

1. with the `(LITERAL)[]` syntax, the parser would not recognize literals
   using type constructors
2. with the syntax `LITERAL[]`, we'd try to store the parsed value
   into a vector

Closes #1860.

(cherry picked from commit f3a0290)

spicy/toolchain/src/compiler/codegen/parsers/types.cc

@@ -46,7 +46,7 @@ struct TypeParser {
         if ( dst )
             return dst;
 
-        if ( meta.field() )
+        if ( meta.field() && meta.isFieldProduction() )
             return builder()->addTmp("x", meta.field()->parseType());
 
         return builder()->addTmp("x", t);

spicy/toolchain/src/compiler/parser/parser.yy

@@ -814,7 +814,7 @@ unit_field_ctor
               | INT64 '(' const_sint ')'         { $$ = builder->ctorSignedInteger($3, 64, __loc__); }
 
 unit_field_in_container
-              : ctor opt_unit_field_args opt_attributes
+              : unit_field_ctor opt_unit_field_args opt_attributes
                                                  { $$ = builder->typeUnitItemUnresolvedField({}, std::move($1), false, std::move($2), {}, {}, std::move($3), {}, {}, __loc__); }
               | scoped_id opt_unit_field_args opt_unit_field_repeat opt_attributes
                                                  { $$ = builder->typeUnitItemUnresolvedField({}, std::move($1), false, std::move($2), std::move($3), {}, std::move($4), {}, {}, __loc__); }

tests/Baseline/spicy.types.vector.ctor-vector/output

@@ -0,0 +1,2 @@
+### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
+[$x1=[0, 0], $x2=[1, 1], $x3=[b"abc", b"abc"]]

tests/spicy/types/vector/ctor-vector.spicy

@@ -0,0 +1,22 @@
+# @TEST-EXEC: ${SCRIPTS}/printf '\x00\x00\x01\x01abcabc' | spicy-driver -d %INPUT >output
+# @TEST-EXEC: btest-diff output
+#
+# @TEST-DOC: Test parsing vectors of constants; regression test for #1860.
+
+module Test;
+
+public type X = unit {
+    x1: (uint8(0))[] foreach {
+        assert $$ == 0: "unreachable";
+    }
+
+    x2: uint8(1)[] foreach {
+        assert $$ == 1: "unreachable";
+    }
+
+    x3: b"abc"[] foreach {
+        assert $$ == b"abc": "unreachable";
+    }
+
+    on %done { print self; }
+};