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Lexical Patcher

Architecture: Pre-Processing Trap Neutralization

Summary: Legacy COBOL frequently relies on outdated control flow structures that break modern Abstract Syntax Tree (AST) parsers. The Lexical Patcher acts as a pre-processor, safely restructuring these traps into deterministic modern equivalents before the main analysis engine engages.

The Dialect Sensor

Because altering mainframe source code carries extreme risk, the patcher first executes a Dialect Sensor to determine the compiler era of the file. It scans for post-1985 structural keywords (e.g., EVALUATE, explicit scope terminators like END-IF). * If the code targets a modern compiler (COBOL-85+), the patcher is cleared to inject modern equivalents. * If the code is constrained to COBOL-74, the patcher engages "ultra-conservative punch-card mode," bypassing modern injections to prevent 0C1 compiler crashes.

Neutralizing NEXT SENTENCE

The NEXT SENTENCE directive is a notoriously dangerous legacy construct that acts as an implicit, invisible GO TO jumping past the next period. This breaks deterministic control flow. * COBOL-85 Mode: The patcher safely rewrites the trap into a localized, block-scoped CONTINUE statement, appending a traceable *> inline comment to document the automated remediation. * COBOL-74 Mode: The patcher leaves the NEXT SENTENCE command intact but cleans the surrounding whitespace to ensure the downstream AST slicer can accurately track the statement without crashing.



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