tree d6306b6956bda5e6055002f4e972f73bc5be7cfe
parent 3921cb6f16f6b9ff340bc9feeaac31db99e18234
author alandonovan <adonovan@google.com> 1611333190 -0500
committer GitHub <noreply@github.com> 1611333190 -0500
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starlark: report "uninitialized cell" errors gracefully (#341)

The contents of a cell may be null, just like any other local.
We should report this as an error.

So that we can name the variable in the error message,
we change the instruction set so that LOCAL<local>+CELL
are combined into a single LOCALCELL<local> instruction,
and FREE<free>+CELL become a single FREECELL<free> instruction.
For symmetry we also combine LOCAL<local>+SETCELL into SETLOCALCELL,
though it cannot fail. (Happily, all three changes are optimizations
previously described by TODO comments.)

Fixes #340