EEx block tag immediately followed by another tag does not parse — `do` block left unterminated and `<% end %>` orphaned

[sh41]

An EEx block-opening tag whose very next thing is another EEx tag, with no template data between them, does not parse. The do block is left unterminated and <% end %> falls outside the tree as an error element, so nothing bound in the block resolves.

<%= if @ok do %><% total = 1 %><%= total %><% end %>

total should resolve to its binding, as the equivalent if ok do total = 1; total end does in plain Elixir. Instead the second tag is swallowed into the first:

ElixirEexTagImpl('<%= if @ok do %><% total = 1 %>')   <- both tags in one
  ElixirDoBlockImpl('do %><% total = 1')
    ElixirStabBodyImpl('total = 1')
    PsiErrorElementImpl('')                            <- unterminated
ElixirEexTagImpl('<%= total %>')
...
PsiErrorElementImpl('end')                             <- orphaned

Any template data before the first nested tag and it parses cleanly and total resolves:

<%= if @ok do %><p>a</p><% total = 1 %><%= total %><% end %>

So it's the adjacency of the two tags. Newlines between them make no difference.

Reproduced on current main in .eex, .leex and .heex. Distinct from #1793, #1414, #1509 and #1661, which are the Don't know how to resolve variable in match tripwire — nothing is logged here, the tree is just wrong — and from the Don't know how to find variable use scope family (#1772, #1831, #1851, #2389), a different message and call site.

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Filed as part of an AI-assisted review of the backlog. A human checked this one before it was filed, but it might still be wrong — if any of it is, please say so here.