Do not allow elements to immediately nest inside themselves.

Plain list is omitted because they can nest.

src/parser/comment.rs

@@ -13,17 +13,27 @@ use nom::sequence::tuple;
 
 use super::util::get_consumed;
 use super::Context;
+use crate::parser::error::CustomError;
+use crate::parser::error::MyError;
 use crate::parser::error::Res;
+use crate::parser::parser_context::ContextElement;
 use crate::parser::parser_with_context::parser_with_context;
 use crate::parser::util::exit_matcher_parser;
+use crate::parser::util::immediate_in_section;
 use crate::parser::util::maybe_consume_trailing_whitespace_if_not_exiting;
 use crate::parser::util::start_of_line;
 use crate::parser::Comment;
 
 #[tracing::instrument(ret, level = "debug")]
 pub fn comment<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str, Comment<'s>> {
-    let comment_line_matcher = parser_with_context!(comment_line)(context);
+    if immediate_in_section(context, "comment") {
-    let exit_matcher = parser_with_context!(exit_matcher_parser)(context);
+        return Err(nom::Err::Error(CustomError::MyError(MyError(
+            "Cannot nest objects of the same element",
+        ))));
+    }
+    let parser_context = context.with_additional_node(ContextElement::Context("comment"));
+    let comment_line_matcher = parser_with_context!(comment_line)(&parser_context);
+    let exit_matcher = parser_with_context!(exit_matcher_parser)(&parser_context);
     let (remaining, first_line) = comment_line_matcher(input)?;
     let (remaining, remaining_lines) =
         many0(preceded(not(exit_matcher), comment_line_matcher))(remaining)?;

src/parser/drawer.rs

@@ -10,6 +10,8 @@ use nom::sequence::tuple;
 
 use super::Context;
 use crate::parser::element::element;
+use crate::parser::error::CustomError;
+use crate::parser::error::MyError;
 use crate::parser::error::Res;
 use crate::parser::exiting::ExitClass;
 use crate::parser::parser_context::ContextElement;
@@ -17,6 +19,7 @@ use crate::parser::parser_context::ExitMatcherNode;
 use crate::parser::parser_with_context::parser_with_context;
 use crate::parser::util::exit_matcher_parser;
 use crate::parser::util::get_consumed;
+use crate::parser::util::immediate_in_section;
 use crate::parser::util::maybe_consume_trailing_whitespace_if_not_exiting;
 use crate::parser::util::start_of_line;
 use crate::parser::util::WORD_CONSTITUENT_CHARACTERS;
@@ -24,6 +27,11 @@ use crate::parser::Drawer;
 
 #[tracing::instrument(ret, level = "debug")]
 pub fn drawer<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str, Drawer<'s>> {
+    if immediate_in_section(context, "drawer") {
+        return Err(nom::Err::Error(CustomError::MyError(MyError(
+            "Cannot nest objects of the same element",
+        ))));
+    }
     start_of_line(context, input)?;
     let (remaining, _leading_whitespace) = space0(input)?;
     let (remaining, (_open_colon, drawer_name, _close_colon, _new_line)) = tuple((
@@ -35,6 +43,7 @@ pub fn drawer<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str,
 
     let parser_context = context
         .with_additional_node(ContextElement::ConsumeTrailingWhitespace(true))
+        .with_additional_node(ContextElement::Context("drawer"))
         .with_additional_node(ContextElement::ExitMatcherNode(ExitMatcherNode {
             class: ExitClass::Alpha,
             exit_matcher: &drawer_end,

src/parser/footnote_definition.rs

@@ -2,6 +2,8 @@ use super::error::Res;
 use super::util::WORD_CONSTITUENT_CHARACTERS;
 use super::Context;
 use crate::parser::element::element;
+use crate::parser::error::CustomError;
+use crate::parser::error::MyError;
 use crate::parser::exiting::ExitClass;
 use crate::parser::greater_element::FootnoteDefinition;
 use crate::parser::parser_context::ContextElement;
@@ -10,6 +12,7 @@ use crate::parser::parser_with_context::parser_with_context;
 use crate::parser::util::blank_line;
 use crate::parser::util::exit_matcher_parser;
 use crate::parser::util::get_consumed;
+use crate::parser::util::immediate_in_section;
 use crate::parser::util::maybe_consume_trailing_whitespace;
 use crate::parser::util::maybe_consume_trailing_whitespace_if_not_exiting;
 use crate::parser::util::start_of_line;
@@ -30,12 +33,18 @@ pub fn footnote_definition<'r, 's>(
     context: Context<'r, 's>,
     input: &'s str,
 ) -> Res<&'s str, FootnoteDefinition<'s>> {
+    if immediate_in_section(context, "footnote definition") {
+        return Err(nom::Err::Error(CustomError::MyError(MyError(
+            "Cannot nest objects of the same element",
+        ))));
+    }
     start_of_line(context, input)?;
     // Cannot be indented.
     let (remaining, (_lead_in, lbl, _lead_out, _ws)) =
         tuple((tag_no_case("[fn:"), label, tag("]"), space0))(input)?;
     let parser_context = context
         .with_additional_node(ContextElement::ConsumeTrailingWhitespace(true))
+        .with_additional_node(ContextElement::Context("footnote definition"))
         .with_additional_node(ContextElement::ExitMatcherNode(ExitMatcherNode {
             class: ExitClass::Alpha,
             exit_matcher: &footnote_definition_end,

src/parser/greater_block.rs

@@ -13,6 +13,7 @@ use crate::parser::parser_with_context::parser_with_context;
 use crate::parser::util::blank_line;
 use crate::parser::util::exit_matcher_parser;
 use crate::parser::util::get_consumed;
+use crate::parser::util::immediate_in_section;
 use crate::parser::util::maybe_consume_trailing_whitespace_if_not_exiting;
 use crate::parser::util::start_of_line;
 use crate::parser::Element;
@@ -35,6 +36,12 @@ pub fn greater_block<'r, 's>(
     context: Context<'r, 's>,
     input: &'s str,
 ) -> Res<&'s str, GreaterBlock<'s>> {
+    // TODO: Do I need to differentiate between different greater block types.
+    if immediate_in_section(context, "greater block") {
+        return Err(nom::Err::Error(CustomError::MyError(MyError(
+            "Cannot nest objects of the same element",
+        ))));
+    }
     start_of_line(context, input)?;
     let (remaining, _leading_whitespace) = space0(input)?;
     // TODO: Not handling indentation before start of block
@@ -49,6 +56,7 @@ pub fn greater_block<'r, 's>(
     let (remaining, _nl) = line_ending(remaining)?;
     let parser_context = context
         .with_additional_node(ContextElement::ConsumeTrailingWhitespace(true))
+        .with_additional_node(ContextElement::Context("greater block"))
         .with_additional_node(ContextElement::GreaterBlock(name))
         .with_additional_node(ContextElement::ExitMatcherNode(ExitMatcherNode {
             class: ExitClass::Alpha,

src/parser/paragraph.rs

@@ -6,12 +6,15 @@ use nom::multi::many1;
 use nom::multi::many_till;
 use nom::sequence::tuple;
 
+use crate::parser::error::CustomError;
+use crate::parser::error::MyError;
 use crate::parser::exiting::ExitClass;
 use crate::parser::object::standard_set_object;
 use crate::parser::parser_context::ContextElement;
 use crate::parser::parser_context::ExitMatcherNode;
 use crate::parser::parser_with_context::parser_with_context;
 use crate::parser::util::exit_matcher_parser;
+use crate::parser::util::immediate_in_section;
 use crate::parser::util::maybe_consume_trailing_whitespace_if_not_exiting;
 use crate::parser::util::start_of_line;
 
@@ -24,8 +27,14 @@ use super::Context;
 
 #[tracing::instrument(ret, level = "debug")]
 pub fn paragraph<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str, Paragraph<'s>> {
-    let parser_context =
+    if immediate_in_section(context, "paragraph") {
-        context.with_additional_node(ContextElement::ExitMatcherNode(ExitMatcherNode {
+        return Err(nom::Err::Error(CustomError::MyError(MyError(
+            "Cannot nest objects of the same element",
+        ))));
+    }
+    let parser_context = context
+        .with_additional_node(ContextElement::Context("paragraph"))
+        .with_additional_node(ContextElement::ExitMatcherNode(ExitMatcherNode {
             class: ExitClass::Beta,
             exit_matcher: &paragraph_end,
         }));

src/parser/plain_list.rs

@@ -35,8 +35,9 @@ use tracing::span;
 
 #[tracing::instrument(ret, level = "debug")]
 pub fn plain_list<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str, PlainList<'s>> {
-    let parser_context =
+    let parser_context = context
-        context.with_additional_node(ContextElement::ExitMatcherNode(ExitMatcherNode {
+        .with_additional_node(ContextElement::Context("plain list"))
+        .with_additional_node(ContextElement::ExitMatcherNode(ExitMatcherNode {
             class: ExitClass::Beta,
             exit_matcher: &plain_list_end,
         }));