Variables declared in the if condition (or in C++17 init-statement) are
visible not only in the if body but also in the else body. But logic in
Tokenizer::setVarIdPass1() handled such variables as if they were
declared in the if body.
As the result they were removed from variablesMap by the time the else
block was parsed and their uses in the else block were either given an
incorrect varId from variables in some outer scope or not given a varId
at all.
This then resulted in false positive unreadVariable errors for variables
declared in the if condition (or init-statement) and used only in the
else block.
Simplification from "else if ..." to "else { if ... }" was moved before
setVarId() to simplify detection for ends of blocks in if-else chains.
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