Give ast::ExprKind::Paren no-op expressions the same ids as their children.

[jseyfried]

Having ast::ExprKind::Paren expressions share ids with their children

• reduces the number of unused NodeIds in the hir map and
• guarantees that tcx.map.expect_expr(ast_expr.id) is the hir corresponding to ast_expr.

This fixes the bug from #34327, which was introduced in #33296 when I assumed the above guarantee.

r? @nrc

[arielb1]

guarantees that tcx.map.expect_expr(ast_expr.id) is the hir corresponding to ast_expr.

This does not sound like a guarantee we want to maintain.

[jseyfried]

@arielb1
Hmm, do you have something in mind that would break that guarantee?
That is, what ast expression besides ExprKind::Paren would not correspond to a unique hir node?

[arielb1]

@jseyfried

We are planning to do a major refactoring of ExprPath and PatPath - there may be problems for patterns.

[jseyfried]

@arielb1 ok, I believe save_analysis only relies on the guarantee for expressions now. If we do break the guarantee, it should be straightforward to fix any fallout in save_analysis.

I'm still not sure which ast nodes besides Paren wouldn't correspond a unique hir node, though.

[nrc]

@bors: r+

[bors]

📌 Commit 24a3a26 has been approved by nrc

[bors]

⌛ Testing commit 24a3a26 with merge ad3e6e6...

[bors]

💔 Test failed - auto-linux-64-opt

[jseyfried]

@bors r=nrc

[bors]

📌 Commit 8557a2e has been approved by nrc