Interpolated strings must not be frozen

tenderlove · tenderlove · commit da09b305ade1 · 2025-07-21T17:15:08.000-07:00
Strings concatenated with backslash may end up being frozen when they shouldn't be. This commit fixes the issue. It required a change upstream in Prism, but also a change to the Prism compiler in CRuby. ruby/prism#3606 [Bug #21187]
diff --git a/prism/prism.c b/prism/prism.c
@@ -5279,6 +5279,10 @@ pm_interpolated_string_node_append(pm_interpolated_string_node_t *node, pm_node_
 
     switch (PM_NODE_TYPE(part)) {
         case PM_STRING_NODE:
+            // If inner string is not frozen, clear flags for this string
+            if (!PM_NODE_FLAG_P(part, PM_STRING_FLAGS_FROZEN)) {
+                CLEAR_FLAGS(node);
+            }
             part->flags = (pm_node_flags_t) ((part->flags | PM_NODE_FLAG_STATIC_LITERAL | PM_STRING_FLAGS_FROZEN) & ~PM_STRING_FLAGS_MUTABLE);
             break;
         case PM_INTERPOLATED_STRING_NODE:
diff --git a/prism_compile.c b/prism_compile.c
@@ -556,7 +556,7 @@ parse_regexp_concat(rb_iseq_t *iseq, const pm_scope_node_t *scope_node, const pm
 static void pm_compile_node(rb_iseq_t *iseq, const pm_node_t *node, LINK_ANCHOR *const ret, bool popped, pm_scope_node_t *scope_node);
 
 static int
-pm_interpolated_node_compile(rb_iseq_t *iseq, const pm_node_list_t *parts, const pm_node_location_t *node_location, LINK_ANCHOR *const ret, bool popped, pm_scope_node_t *scope_node, rb_encoding *implicit_regexp_encoding, rb_encoding *explicit_regexp_encoding)
+pm_interpolated_node_compile(rb_iseq_t *iseq, const pm_node_list_t *parts, const pm_node_location_t *node_location, LINK_ANCHOR *const ret, bool popped, pm_scope_node_t *scope_node, rb_encoding *implicit_regexp_encoding, rb_encoding *explicit_regexp_encoding, bool mutable_result)
 {
     int stack_size = 0;
     size_t parts_size = parts->size;
@@ -666,7 +666,7 @@ pm_interpolated_node_compile(rb_iseq_t *iseq, const pm_node_list_t *parts, const
         if (RTEST(current_string)) {
             current_string = rb_fstring(current_string);
 
-            if (stack_size == 0 && interpolated) {
+            if (stack_size == 0 && (interpolated || mutable_result)) {
                 PUSH_INSN1(ret, current_location, putstring, current_string);
             }
             else {
@@ -690,7 +690,7 @@ pm_compile_regexp_dynamic(rb_iseq_t *iseq, const pm_node_t *node, const pm_node_
     rb_encoding *explicit_regexp_encoding = parse_regexp_encoding(scope_node, node);
     rb_encoding *implicit_regexp_encoding = explicit_regexp_encoding != NULL ? explicit_regexp_encoding : scope_node->encoding;
 
-    int length = pm_interpolated_node_compile(iseq, parts, node_location, ret, popped, scope_node, implicit_regexp_encoding, explicit_regexp_encoding);
+    int length = pm_interpolated_node_compile(iseq, parts, node_location, ret, popped, scope_node, implicit_regexp_encoding, explicit_regexp_encoding, false);
     PUSH_INSN2(ret, *node_location, toregexp, INT2FIX(parse_regexp_flags(node) & 0xFF), INT2FIX(length));
 }
 
@@ -9637,7 +9637,7 @@ pm_compile_node(rb_iseq_t *iseq, const pm_node_t *node, LINK_ANCHOR *const ret,
         }
         else {
             const pm_interpolated_string_node_t *cast = (const pm_interpolated_string_node_t *) node;
-            int length = pm_interpolated_node_compile(iseq, &cast->parts, &location, ret, popped, scope_node, NULL, NULL);
+            int length = pm_interpolated_node_compile(iseq, &cast->parts, &location, ret, popped, scope_node, NULL, NULL, !PM_NODE_FLAG_P(cast, PM_INTERPOLATED_STRING_NODE_FLAGS_FROZEN));
             if (length > 1) PUSH_INSN1(ret, location, concatstrings, INT2FIX(length));
             if (popped) PUSH_INSN(ret, location, pop);
         }
@@ -9648,7 +9648,7 @@ pm_compile_node(rb_iseq_t *iseq, const pm_node_t *node, LINK_ANCHOR *const ret,
         // :"foo #{bar}"
         // ^^^^^^^^^^^^^
         const pm_interpolated_symbol_node_t *cast = (const pm_interpolated_symbol_node_t *) node;
-        int length = pm_interpolated_node_compile(iseq, &cast->parts, &location, ret, popped, scope_node, NULL, NULL);
+        int length = pm_interpolated_node_compile(iseq, &cast->parts, &location, ret, popped, scope_node, NULL, NULL, false);
 
         if (length > 1) {
             PUSH_INSN1(ret, location, concatstrings, INT2FIX(length));
@@ -9670,7 +9670,7 @@ pm_compile_node(rb_iseq_t *iseq, const pm_node_t *node, LINK_ANCHOR *const ret,
 
         PUSH_INSN(ret, location, putself);
 
-        int length = pm_interpolated_node_compile(iseq, &cast->parts, &location, ret, false, scope_node, NULL, NULL);
+        int length = pm_interpolated_node_compile(iseq, &cast->parts, &location, ret, false, scope_node, NULL, NULL, false);
         if (length > 1) PUSH_INSN1(ret, location, concatstrings, INT2FIX(length));
 
         PUSH_SEND_WITH_FLAG(ret, location, idBackquote, INT2NUM(1), INT2FIX(VM_CALL_FCALL | VM_CALL_ARGS_SIMPLE));
diff --git a/test/prism/result/static_literals_test.rb b/test/prism/result/static_literals_test.rb
@@ -4,6 +4,11 @@
 
 module Prism
   class StaticLiteralsTest < TestCase
+    def test_concatenanted_string_literal_is_not_static
+      node = Prism.parse_statement("'a' 'b'")
+      refute_predicate node, :static_literal?
+    end
+
     def test_static_literals
       assert_warning("1")
       assert_warning("0xA", "10", "10")
