Fix label interpolated string

Author: kddnewton

config.yml

@@ -3306,6 +3306,9 @@ nodes:
           - EmbeddedVariableNode
           - InterpolatedStringNode # `"a" "#{b}"`
           - on error: XStringNode # `<<`FOO` "bar"
+          - on error: InterpolatedXStringNode
+          - on error: SymbolNode
+          - on error: InterpolatedSymbolNode
       - name: closing_loc
         type: location?
     newline: parts

src/prism.c

@@ -5344,8 +5344,10 @@ pm_interpolated_string_node_append(pm_interpolated_string_node_t *node, pm_node_
             break;
         case PM_X_STRING_NODE:
         case PM_INTERPOLATED_X_STRING_NODE:
-            // If this is an x string, then this is a syntax error. But we want
-            // to handle it here so that we don't fail the assertion.
+        case PM_SYMBOL_NODE:
+        case PM_INTERPOLATED_SYMBOL_NODE:
+            // These will only happen in error cases. But we want to handle it
+            // here so that we don't fail the assertion.
             CLEAR_FLAGS(node);
             break;
         default:

test/prism/errors/label_in_interpolated_string.txt

@@ -0,0 +1,14 @@
+case    in el""Q
+^~~~ expected a predicate for a case matching statement
+             ^ expected a delimiter after the patterns of an `in` clause
+               ^ unexpected constant, expecting end-of-input
+ !"""#{in el"":Q
+       ^~ unexpected 'in', assuming it is closing the parent 'in' clause
+       ^ expected a `}` to close the embedded expression
+       ^~ cannot parse the string part
+          ^~ cannot parse the string part
+            ^ cannot parse the string part
+    ^~~~~~~~~~~ unexpected label
+    ^~~~~~~~~~~ expected a string for concatenation
+               ^ expected an `end` to close the `case` statement
+