Use === in more places to reduce invalidation

Author: timholy

src/match/macro.jl

@@ -39,7 +39,7 @@ function clauses(ex)
   for l in ex.args
     isline(l) && (line = l; continue)
     env = trymatch(:(pat_ => yes_), l)
-    env == nothing && error("Invalid match clause $l")
+    env === nothing && error("Invalid match clause $l")
     pat, yes = env[:pat], env[:yes]
     push!(clauses, (pat, :($line;$yes)))
   end
@@ -70,7 +70,7 @@ macro capture(ex, pat)
   quote
     $([:($(esc(b)) = nothing) for b in bs]...)
     env = trymatch($(esc(Expr(:quote, pat))), $(esc(ex)))
-    if env == nothing
+    if env === nothing
       false
     else
       $([:($(esc(b)) = get(env, $(esc(Expr(:quote, b))), nothing)) for b in bs]...)

src/match/match.jl

@@ -96,7 +96,7 @@ match(::LineNumberNode, ::LineNumberNode, _) = nothing
 
 function match(pat, ex, env)
   pat = normalise(pat)
-  pat == :_ && return env
+  pat === :_ && return env
   isbinding(pat) && return store!(env, bname(pat), ex)
   ex = normalise(ex)
   pat, ex = blockunify(pat, ex)

src/match/union.jl

@@ -8,7 +8,7 @@ or_(p...) = foldl(or_, p)
 
 function match_inner(pat::OrBind, ex, env)
   env′ = trymatch(pat.pat1, ex)
-  env′ == nothing ? match(pat.pat2, ex, env) : merge!(env, env′)
+  env′ === nothing ? match(pat.pat2, ex, env) : merge!(env, env′)
 end
 
 function isor(ex)