Switch to Vec of MatchPairs

Because I'm about to make MatchPair recursive, which I can't do with
SmallVec, and I need to share code between the two.

Author: Nadrieril

compiler/rustc_mir_build/src/build/matches/mod.rs

@@ -22,8 +22,6 @@ use rustc_middle::ty::{self, CanonicalUserTypeAnnotation, Ty};
 use rustc_span::symbol::Symbol;
 use rustc_span::{BytePos, Pos, Span};
 use rustc_target::abi::VariantIdx;
-use smallvec::{smallvec, SmallVec};
-
 // helper functions, broken out by category:
 mod simplify;
 mod test;
@@ -951,7 +949,7 @@ struct Candidate<'pat, 'tcx> {
     has_guard: bool,
 
     /// All of these must be satisfied...
-    match_pairs: SmallVec<[MatchPair<'pat, 'tcx>; 1]>,
+    match_pairs: Vec<MatchPair<'pat, 'tcx>>,
 
     /// ...these bindings established...
     bindings: Vec<Binding<'tcx>>,
@@ -981,7 +979,7 @@ impl<'tcx, 'pat> Candidate<'pat, 'tcx> {
         Candidate {
             span: pattern.span,
             has_guard,
-            match_pairs: smallvec![MatchPair::new(place, pattern, cx)],
+            match_pairs: vec![MatchPair::new(place, pattern, cx)],
             bindings: Vec::new(),
             ascriptions: Vec::new(),
             subcandidates: Vec::new(),

compiler/rustc_mir_build/src/build/matches/util.rs

@@ -6,7 +6,6 @@ use rustc_middle::mir::*;
 use rustc_middle::thir::*;
 use rustc_middle::ty;
 use rustc_middle::ty::TypeVisitableExt;
-use smallvec::SmallVec;
 
 impl<'a, 'tcx> Builder<'a, 'tcx> {
     pub(crate) fn field_match_pairs<'pat>(
@@ -26,7 +25,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
 
     pub(crate) fn prefix_slice_suffix<'pat>(
         &mut self,
-        match_pairs: &mut SmallVec<[MatchPair<'pat, 'tcx>; 1]>,
+        match_pairs: &mut Vec<MatchPair<'pat, 'tcx>>,
         place: &PlaceBuilder<'tcx>,
         prefix: &'pat [Box<Pat<'tcx>>],
         opt_slice: &'pat Option<Box<Pat<'tcx>>>,