[rust-compiler] Use rustc-hash FxHasher for all maps and sets (#36811)

Why

FxHasher is a simple, fast, non-cryptographic hasher. std's default (SipHash) is DoS-resistant but heavy - the compiler keys maps/sets almost entirely on small integer IDs (IdentifierId, BlockId, ScopeId, …) where that protection buys nothing. Switching gives:

• Performance - faster hashing on the hot ID-keyed maps/sets used throughout the passes.
• Slight binary size reduction - drops the heavy SipHash hasher pulled in by std's HashMap/HashSet.

Changes

• std::collections::HashMap/HashSet → rustc_hash::FxHashMap/FxHashSet
• indexmap IndexMap/IndexSet now use FxBuildHasher, inlined as IndexMap<K, V, FxBuildHasher> (no FxIndexMap type aliases)
• rustc-hash = "2" added to all 12 crate manifests
• rustc_hash/indexmap imports consolidated into single brace imports at the top of each file

The change is serde-neutral: FxHashMap and IndexMap<_, _, FxBuildHasher> serialize to byte-identical JSON, and IndexMap keeps insertion order. cargo check, cargo fmt --check, and cargo test all pass with no warnings.

Commit 06b2a50 authored - 1 parent 53b5c3c - 89 files changed, 1036 additions & 961 deletions.

File tree

• compiler
  • crates
    • react_compiler_ast
      • src
    • react_compiler_diagnostics
      • src
    • react_compiler_hir
      • src
    • react_compiler_inference
      • src
    • react_compiler_lowering
      • src
    • react_compiler_optimization
      • src
    • react_compiler_reactive_scopes
      • src
    • react_compiler_ssa
      • src
    • react_compiler_typeinference
      • src
    • react_compiler_utils
      • src
    • react_compiler_validation
      • src
    • react_compiler
      • src/entrypoint