Match expressions use O(n) stack space with n branches in debug mode #34283
Description
I ran into this problem while working on a parser (https://github.com/evanw/esbuild/tree/rust). Here's a reduced test case: https://gist.github.com/evanw/06e074a1d6d5c21e8d32e2c26de07714. It contains two recursive functions, small and large, that each contain a match expression. Every call prints out the amount of stack space used.
In debug:
small:
stack space: 0.3kb
stack space: 0.7kb
stack space: 1.0kb
stack space: 1.4kb
stack space: 1.7kb
stack space: 2.1kb
stack space: 2.4kb
stack space: 2.8kb
stack space: 3.1kb
stack space: 3.4kb
stack space: 3.8kb
large:
stack space: 0.6kb
stack space: 1.3kb
stack space: 1.9kb
stack space: 2.6kb
stack space: 3.2kb
stack space: 3.8kb
stack space: 4.5kb
stack space: 5.1kb
stack space: 5.8kb
stack space: 6.4kb
stack space: 7.0kb
In release:
small:
stack space: 0.0kb
stack space: 0.1kb
stack space: 0.2kb
stack space: 0.4kb
stack space: 0.5kb
stack space: 0.6kb
stack space: 0.7kb
stack space: 0.8kb
stack space: 0.9kb
stack space: 1.0kb
stack space: 1.1kb
large:
stack space: 0.0kb
stack space: 0.1kb
stack space: 0.2kb
stack space: 0.4kb
stack space: 0.5kb
stack space: 0.6kb
stack space: 0.7kb
stack space: 0.8kb
stack space: 0.9kb
stack space: 1.0kb
stack space: 1.1kb
I would expect the amount of stack space used by a match expression to be proportional to the stack space of the largest branch, not to the total stack space of all branches. The problem isn't too bad here but it causes my actual parser to use huge amounts of stack space and to crash with a stack overflow when parsing virtually all normal-sized inputs.