Reject adjacent string literals#5340
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The parser's TK_NEWLINE check compared the start lines of the previous and current tokens to decide whether a real newline separated them. For multi-line string literals this is wrong: the token's start line is the line of the opening quote, but the next token can sit on the same physical line as the string's closing quote. As a result, adjacent string literals across multi-line strings slipped past the missing-semicolon check and silently parsed as two expressions inside the same construct. Track on each token whether a real newline character preceded it, and consult that flag from the parser instead of comparing line numbers. The lexer maintains this as a separate flag from the existing `lexer->newline` that drives LPAREN_NEW etc., because block comments intentionally suppress the latter while needing to preserve the former. Closes #3836
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The parser silently accepted two adjacent string literals across a multi-line string boundary as two separate expressions inside the same construct. A typo involving
"""would produce a program that compiled but behaved nothing like what was written. The compiler now reports a missing-semicolon error in that case.Closes #3836