Make variant_fields inner an IndexVec

src/librustc/mir/mod.rs

@@ -2997,7 +2997,7 @@ pub struct UnsafetyCheckResult {
 /// The layout of generator state
 #[derive(Clone, Debug, RustcEncodable, RustcDecodable, HashStable)]
 pub struct GeneratorLayout<'tcx> {
-    pub variant_fields: IndexVec<VariantIdx, Vec<LocalDecl<'tcx>>>,
+    pub variant_fields: IndexVec<VariantIdx, IndexVec<Field, LocalDecl<'tcx>>>,
 }
 
 #[derive(Clone, Debug, RustcEncodable, RustcDecodable, HashStable)]

src/librustc_codegen_llvm/debuginfo/metadata.rs

@@ -1598,7 +1598,7 @@ fn field_name(&self, i: usize) -> String {
                 Some(variant.fields[i].ident.to_string()),
             VariantInfo::Generator(_, generator_layout, variant_index) => {
                 let variant_decls = &generator_layout.variant_fields[*variant_index];
-                variant_decls[i].name.map(|name| name.to_string())
+                variant_decls[i.into()].name.map(|name| name.to_string())
             }
             _ => None,
         };

src/librustc_mir/transform/generator.rs

@@ -58,7 +58,7 @@
 use rustc::ty::layout::VariantIdx;
 use rustc::ty::subst::SubstsRef;
 use rustc_data_structures::fx::FxHashMap;
-use rustc_data_structures::indexed_vec::Idx;
+use rustc_data_structures::indexed_vec::{Idx, IndexVec};
 use rustc_data_structures::bit_set::BitSet;
 use std::borrow::Cow;
 use std::iter;
@@ -560,7 +560,7 @@ fn compute_layout<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     }).unzip();
 
     // Put every var in each variant, for now.
-    let empty_variants = iter::repeat(vec![]).take(3);
+    let empty_variants = iter::repeat(IndexVec::new()).take(3);
     let state_variants = iter::repeat(vars).take(suspending_blocks.count());
     let layout = GeneratorLayout {
         variant_fields: empty_variants.chain(state_variants).collect()