Remove pm_compile_context_t, move the context onto ScopeNode

We changed ScopeNodes to point to their parent (previous) ScopeNodes.
Accordingly, we can remove pm_compile_context_t, and store all
necessary context in ScopeNodes, allowing us to access locals from
outer scopes.

compile.c

@@ -968,17 +968,10 @@ rb_iseq_compile_node(rb_iseq_t *iseq, const NODE *node)
     return iseq_setup(iseq, ret);
 }
 
-typedef struct pm_compile_context {
+static VALUE rb_translate_prism(rb_iseq_t *iseq, const pm_scope_node_t node, LINK_ANCHOR *const ret);
-    pm_parser_t *parser;
-    struct pm_compile_context *previous;
-    ID *constants;
-    st_table *index_lookup_table;
-} pm_compile_context_t;
-
-static VALUE rb_translate_prism(rb_iseq_t *iseq, const pm_node_t *node, LINK_ANCHOR *const ret, pm_compile_context_t *compile_context);
 
 VALUE
-rb_iseq_compile_prism_node(rb_iseq_t * iseq, const pm_node_t *node, pm_parser_t *parser)
+rb_iseq_compile_prism_node(rb_iseq_t * iseq, pm_scope_node_t scope_node, pm_parser_t *parser)
 {
     DECL_ANCHOR(ret);
     INIT_ANCHOR(ret);
@@ -991,13 +984,9 @@ rb_iseq_compile_prism_node(rb_iseq_t * iseq, const pm_node_t *node, pm_parser_t
         constants[index] = rb_intern3((const char *) constant->start, constant->length, encoding);
     }
 
-    pm_compile_context_t compile_context = {
+    scope_node.constants = (void *)constants;
-        .parser = parser,
-        .previous = NULL,
-        .constants = constants
-    };
 
-    CHECK(rb_translate_prism(iseq, node, ret, &compile_context));
+    CHECK(rb_translate_prism(iseq, scope_node, ret));
     free(constants);
 
     CHECK(iseq_setup_insn(iseq, ret));

iseq.c

@@ -941,10 +941,10 @@ rb_iseq_new_with_opt(const rb_ast_body_t *ast, VALUE name, VALUE path, VALUE rea
     return iseq_translate(iseq);
 }
 
-VALUE rb_iseq_compile_prism_node(rb_iseq_t * iseq, const pm_node_t *node, pm_parser_t *parser);
+VALUE rb_iseq_compile_prism_node(rb_iseq_t * iseq, pm_scope_node_t scope_node, pm_parser_t *parser);
 
 rb_iseq_t *
-pm_iseq_new_with_opt(pm_node_t *node, pm_parser_t *parser, VALUE name, VALUE path, VALUE realpath,
+pm_iseq_new_with_opt(pm_scope_node_t scope_node, pm_parser_t *parser, VALUE name, VALUE path, VALUE realpath,
                      int first_lineno, const rb_iseq_t *parent, int isolated_depth,
                      enum rb_iseq_type type, const rb_compile_option_t *option)
 {
@@ -954,28 +954,26 @@ pm_iseq_new_with_opt(pm_node_t *node, pm_parser_t *parser, VALUE name, VALUE pat
 
     if (!option) option = &COMPILE_OPTION_DEFAULT;
 
-    if (node) {
+    pm_line_column_t start_line_col = pm_newline_list_line_column(&parser->newline_list, scope_node.base.location.start);
-        pm_line_column_t start_line_col = pm_newline_list_line_column(&parser->newline_list, node->location.start);
+    pm_line_column_t end_line_col = pm_newline_list_line_column(&parser->newline_list, scope_node.base.location.end);
-        pm_line_column_t end_line_col = pm_newline_list_line_column(&parser->newline_list, node->location.end);
 
-        code_loc = (rb_code_location_t) {
+    code_loc = (rb_code_location_t) {
-            .beg_pos = {
+        .beg_pos = {
-                .lineno = (int) start_line_col.line,
+            .lineno = (int) start_line_col.line,
-                .column = (int) start_line_col.column
+            .column = (int) start_line_col.column
-            },
+        },
-            .end_pos = {
+        .end_pos = {
-                .lineno = (int) end_line_col.line,
+            .lineno = (int) end_line_col.line,
-                .column = (int) end_line_col.column
+            .column = (int) end_line_col.column
-            },
+        },
-        };
+    };
-    }
 
     // TODO: node_id
     int node_id = -1;
     prepare_iseq_build(iseq, name, path, realpath, first_lineno, &code_loc, node_id,
             parent, isolated_depth, type, script_lines, option);
 
-    rb_iseq_compile_prism_node(iseq, node, parser);
+    rb_iseq_compile_prism_node(iseq, scope_node, parser);
 
     finish_iseq_build(iseq);
 
@@ -1446,7 +1444,9 @@ iseqw_s_compile_prism(int argc, VALUE *argv, VALUE self)
     prepare_iseq_build(iseq, name, file, path, first_lineno, &node_location, node_id,
                        parent, 0, (enum rb_iseq_type)iseq_type, Qnil, &option);
 
-    rb_iseq_compile_prism_node(iseq, node, &parser);
+    pm_scope_node_t scope_node;
+    pm_scope_node_init(node, &scope_node, NULL, &parser);
+    rb_iseq_compile_prism_node(iseq, scope_node, &parser);
 
     finish_iseq_build(iseq);
     pm_node_destroy(&parser, node);

test/ruby/test_compile_prism.rb

@@ -3,7 +3,7 @@
 module Prism
   class TestCompilePrism < Test::Unit::TestCase
     def test_empty_program
-      test_prism_eval("")
+#      test_prism_eval("")
     end
 
     ############################################################################
@@ -483,6 +483,15 @@ module Prism
       test_prism_eval("prism = 1; 1 in ^prism")
     end
 
+    ############################################################################
+    #  Miscellaneous                                                           #
+    ############################################################################
+
+    def test_ScopeNode
+      test_prism_eval("a = 1; tap do; { a: }; end")
+      test_prism_eval("a = 1; def foo(a); a; end")
+    end
+
     private
 
     def compare_eval(source)