html: fix svg and math detection

Previously we would still attempt to match html elements inside of svg
and math contexts. Fixing this bug required adding extra logic to notice
when, from inside those contexts, we detect a closing svg/math tag that
would bring us back into an HTML context.

Author: kristoff-it

src/html/Ast.zig

@@ -601,39 +601,40 @@ pub fn init(
                                             .after => nodes.items[current_idx].parent_idx,
                                         };
 
-                                    const e = elements.get(kind);
-                                    const model = if (syntax_only or language != .html)
-                                        undefined
-                                    else
-                                        try e.validateAttrs(
-                                            gpa,
-                                            language,
-                                            &errors,
-                                            &seen_attrs,
-                                            &seen_ids_stack.items[seen_ids_stack.items.len - 1],
-                                            nodes.items,
-                                            parent_idx,
-                                            src,
-                                            tag.span,
-                                            @intCast(nodes.items.len),
-                                        );
-
-                                    if (kind == .template) {
-                                        try seen_ids_stack.append(gpa, .empty);
+                                        const e = elements.get(kind);
+                                        const model = if (syntax_only or language != .html)
+                                            undefined
+                                        else
+                                            try e.validateAttrs(
+                                                gpa,
+                                                language,
+                                                &errors,
+                                                &seen_attrs,
+                                                &seen_ids_stack.items[seen_ids_stack.items.len - 1],
+                                                nodes.items,
+                                                parent_idx,
+                                                src,
+                                                tag.span,
+                                                @intCast(nodes.items.len),
+                                            );
+
+                                        if (kind == .template) {
+                                            try seen_ids_stack.append(gpa, .empty);
+                                        }
+
+                                        break :node .{
+                                            .open = tag.span,
+                                            .kind = kind,
+                                            .model = model,
+                                            .self_closing = self_closing,
+                                        };
+                                    } else if (std.mem.indexOfScalar(u8, name, '-') == null and !syntax_only) {
+                                        try errors.append(gpa, .{
+                                            .tag = .invalid_html_tag_name,
+                                            .main_location = tag.name,
+                                            .node_idx = @intCast(nodes.items.len),
+                                        });
                                     }
-
-                                    break :node .{
-                                        .open = tag.span,
-                                        .kind = kind,
-                                        .model = model,
-                                        .self_closing = self_closing,
-                                    };
-                                } else if (std.mem.indexOfScalar(u8, name, '-') == null and !syntax_only) {
-                                    try errors.append(gpa, .{
-                                        .tag = .invalid_html_tag_name,
-                                        .main_location = tag.name,
-                                        .node_idx = @intCast(nodes.items.len),
-                                    });
                                 }
 
                                 break :node .{
@@ -752,7 +753,11 @@ pub fn init(
                     }
 
                     const name = tag.name.slice(src);
-                    const end_kind = switch (language) {
+                    const end_kind = if (svg_lvl == 1 and std.ascii.eqlIgnoreCase(name, "svg"))
+                        .svg
+                    else if (math_lvl == 1 and std.ascii.eqlIgnoreCase(name, "math"))
+                        .math
+                    else if (svg_lvl != 0 or math_lvl != 0) .___ else switch (language) {
                         .superhtml => if (std.ascii.eqlIgnoreCase("ctx", name))
                             .ctx
                         else if (std.ascii.eqlIgnoreCase("super", name))