Remove three-phase exhale: No reordering of conjuncts during exhale.#411
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Currently, Carbon potentially reorders conjuncts when exhaling an assertion. For example, Carbon verifies
inhale acc(x.f); exhale acc(x.f,wildcard) && acc(x.f,1/2), because Carbon first exhalesacc(x.f,1/2)and thenexhales acc(x.f,wildcard). The technique behind this multiphase exhale is described in "Abstract Read Permissions: Fractional Permissions without the Fractions (S. Heule and K. R. M. Leino and P. Müller and A. J. Summers; VMCAI 2013)" and "Constraint Semantics for Abstract Read Permissions Formal Techniques for Java-like Programs (J. Boyland and P. Müller and M. Schwerhoff and A. J. Summers; FTfJP 2014)".The Viper team has decided to drop this reordering feature (which was never implemented in Silicon). This pull request gets rid of the reordering technique implemented in Carbon during an exhale.