Check in initial diff engine and semantic analysis #7

Job	Run time
Test Suite (windows-latest, stable)	25s
Security Audit	5m 16s
Test Suite (ubuntu-latest, stable)	19s
Test Suite (windows-latest, beta)	34s
Test Suite (macos-latest, beta)	31s
Test Suite (ubuntu-latest, beta)	19s
Test Suite (macos-latest, stable)	25s
Build Release	-1s
	7m 48s

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