rustc runs out of memory when compiling an `if` statement with no block, enclosed in parentheses

[kuretchi]

I tried this code:

fn main() {
    (if foobar)
}

$ ulimit -v 2000000  # 2 GB
$ rustc main.rs

rustc first outputs some error messages and then hangs up trying to allocate a large amount of memory.

error: expected `{`, found `)`
 --> main.rs:2:15
  |
2 |     (if foobar)
  |      --       ^ expected `{`
  |      |
  |      this `if` statement has a condition, but no block

error: expected expression, found `<eof>`
 --> main.rs:3:1
  |
3 | }
  | ^ expected expression

memory allocation of 1610612736 bytes failedAborted (core dumped)

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rustc --version --verbose:

rustc 1.35.0 (3c235d560 2019-05-20)
binary: rustc
commit-hash: 3c235d5600393dfe6c36eeed34042efad8d4f26e
commit-date: 2019-05-20
host: x86_64-unknown-linux-gnu
release: 1.35.0
LLVM version: 8.0

[tesuji]

@rustbot modify labels: regression-from-stable-to-nightly

[rustbot]

Error: Label regression-from-stable-to-nightly can only be set by Rust team members

Please let @rust-lang/release know if you're having trouble with this bot.

[tesuji]

Rust 1.34.0 and before is OK: https://godbolt.org/z/dFMxwR

[pnkfelix]

triage: P-medium. Removing nomination. Assigning to self and @estebank for initial investigation.