diff --git a/base/cartesian.jl b/base/cartesian.jl
index 45276e918b17c..f5825f56ba1aa 100644
--- a/base/cartesian.jl
+++ b/base/cartesian.jl
@@ -353,8 +353,13 @@ const exprresolve_cond_dict = Dict{Symbol,Function}(:(==) => ==,
     :(<) => <, :(>) => >, :(<=) => <=, :(>=) => >=)
 
 function exprresolve_arith(ex::Expr)
-    if ex.head === :call && haskey(exprresolve_arith_dict, ex.args[1]) && all([isa(ex.args[i], Number) for i = 2:length(ex.args)])
-        return true, exprresolve_arith_dict[ex.args[1]](ex.args[2:end]...)
+    if ex.head === :call
+        callee = ex.args[1]
+        if isa(callee, Symbol)
+            if haskey(exprresolve_arith_dict, callee) && all(Bool[isa(ex.args[i], Number) for i = 2:length(ex.args)])
+                return true, exprresolve_arith_dict[callee](ex.args[2:end]...)
+            end
+        end
     end
     false, 0
 end
@@ -362,8 +367,13 @@ exprresolve_arith(arg) = false, 0
 
 exprresolve_conditional(b::Bool) = true, b
 function exprresolve_conditional(ex::Expr)
-    if ex.head === :call && ex.args[1] ∈ keys(exprresolve_cond_dict) && isa(ex.args[2], Number) && isa(ex.args[3], Number)
-        return true, exprresolve_cond_dict[ex.args[1]](ex.args[2], ex.args[3])
+    if ex.head === :call
+        callee = ex.args[1]
+        if isa(callee, Symbol)
+            if callee ∈ keys(exprresolve_cond_dict) && isa(ex.args[2], Number) && isa(ex.args[3], Number)
+                return true, exprresolve_cond_dict[callee](ex.args[2], ex.args[3])
+            end
+        end
     end
     false, false
 end
diff --git a/base/docs/Docs.jl b/base/docs/Docs.jl
index 8ba3949082008..50a13244451aa 100644
--- a/base/docs/Docs.jl
+++ b/base/docs/Docs.jl
@@ -225,7 +225,7 @@ function doc!(__module__::Module, b::Binding, str::DocStr, @nospecialize sig = U
         # We allow for docstrings to be updated, but print a warning since it is possible
         # that over-writing a docstring *may* have been accidental.  The warning
         # is suppressed for symbols in Main, for interactive use (#23011).
-        __module__ == Main || @warn "Replacing docs for `$b :: $sig` in module `$(__module__)`"
+        __module__ === Main || @warn "Replacing docs for `$b :: $sig` in module `$(__module__)`"
     else
         # The ordering of docstrings for each Binding is defined by the order in which they
         # are initially added. Replacing a specific docstring does not change it's ordering.
diff --git a/base/errorshow.jl b/base/errorshow.jl
index fb73d480261c3..40800f0bc15a3 100644
--- a/base/errorshow.jl
+++ b/base/errorshow.jl
@@ -380,7 +380,7 @@ function show_method_candidates(io::IO, ex::MethodError, @nospecialize kwargs=()
     ft = typeof(f)
     lines = []
     # These functions are special cased to only show if first argument is matched.
-    special = f in [convert, getindex, setindex!]
+    special = f === convert || f === getindex || f === setindex!
     funcs = Any[(f, arg_types_param)]
 
     # An incorrect call method produces a MethodError for convert.
@@ -682,7 +682,7 @@ function _simplify_include_frames(trace)
     kept_frames = trues(i)
     first_ignored = nothing
     while i >= 1
-        frame, _ = trace[i]
+        frame::StackFrame, _ = trace[i]
         mod = parentmodule(frame)
         if isnothing(first_ignored)
             if mod === Base && frame.func === :_include
diff --git a/base/multimedia.jl b/base/multimedia.jl
index 4729849cfbc8d..576623202c7f8 100644
--- a/base/multimedia.jl
+++ b/base/multimedia.jl
@@ -327,7 +327,7 @@ function display(@nospecialize x)
             try
                 return display(displays[i], x)
             catch e
-                isa(e, MethodError) && e.f in (display, show) ||
+                isa(e, MethodError) && (e.f === display || e.f === show) ||
                     rethrow()
             end
         end
diff --git a/stdlib/Distributed/src/Distributed.jl b/stdlib/Distributed/src/Distributed.jl
index dbeaf6282f920..bb641ac9c2d83 100644
--- a/stdlib/Distributed/src/Distributed.jl
+++ b/stdlib/Distributed/src/Distributed.jl
@@ -82,6 +82,20 @@ function _require_callback(mod::Base.PkgId)
     end
 end
 
+const REF_ID = Ref(1)
+next_ref_id() = (id = REF_ID[]; REF_ID[] = id+1; id)
+
+struct RRID
+    whence::Int
+    id::Int
+
+    RRID() = RRID(myid(),next_ref_id())
+    RRID(whence, id) = new(whence,id)
+end
+
+hash(r::RRID, h::UInt) = hash(r.whence, hash(r.id, h))
+==(r::RRID, s::RRID) = (r.whence==s.whence && r.id==s.id)
+
 include("clusterserialize.jl")
 include("cluster.jl")   # cluster setup and management, addprocs
 include("messages.jl")
diff --git a/stdlib/Distributed/src/cluster.jl b/stdlib/Distributed/src/cluster.jl
index 9bdfde7f920d4..8c5bfa102b387 100644
--- a/stdlib/Distributed/src/cluster.jl
+++ b/stdlib/Distributed/src/cluster.jl
@@ -148,7 +148,7 @@ function set_worker_state(w, state)
 end
 
 function check_worker_state(w::Worker)
-    if w.state == W_CREATED
+    if w.state === W_CREATED
         if !isclusterlazy()
             if PGRP.topology === :all_to_all
                 # Since higher pids connect with lower pids, the remote worker
@@ -185,13 +185,13 @@ function exec_conn_func(w::Worker)
 end
 
 function wait_for_conn(w)
-    if w.state == W_CREATED
+    if w.state === W_CREATED
         timeout =  worker_timeout() - (time() - w.ct_time)
         timeout <= 0 && error("peer $(w.id) has not connected to $(myid())")
 
         @async (sleep(timeout); notify(w.c_state; all=true))
         wait(w.c_state)
-        w.state == W_CREATED && error("peer $(w.id) didn't connect to $(myid()) within $timeout seconds")
+        w.state === W_CREATED && error("peer $(w.id) didn't connect to $(myid()) within $timeout seconds")
     end
     nothing
 end
@@ -626,7 +626,7 @@ function create_worker(manager, wconfig)
         # require the value of config.connect_at which is set only upon connection completion
         for jw in PGRP.workers
             if (jw.id != 1) && (jw.id < w.id)
-                (jw.state == W_CREATED) && wait(jw.c_state)
+                (jw.state === W_CREATED) && wait(jw.c_state)
                 push!(join_list, jw)
             end
         end
@@ -649,7 +649,7 @@ function create_worker(manager, wconfig)
         end
 
         for wl in wlist
-            (wl.state == W_CREATED) && wait(wl.c_state)
+            (wl.state === W_CREATED) && wait(wl.c_state)
             push!(join_list, wl)
         end
     end
@@ -767,7 +767,7 @@ end
 mutable struct ProcessGroup
     name::AbstractString
     workers::Array{Any,1}
-    refs::Dict                  # global references
+    refs::Dict{RRID,Any}                  # global references
     topology::Symbol
     lazy::Union{Bool, Nothing}
 
@@ -851,7 +851,7 @@ function nprocs()
         n = length(PGRP.workers)
         # filter out workers in the process of being setup/shutdown.
         for jw in PGRP.workers
-            if !isa(jw, LocalProcess) && (jw.state != W_CONNECTED)
+            if !isa(jw, LocalProcess) && (jw.state !== W_CONNECTED)
                 n = n - 1
             end
         end
@@ -902,7 +902,7 @@ julia> procs()
 function procs()
     if myid() == 1 || (PGRP.topology === :all_to_all  && !isclusterlazy())
         # filter out workers in the process of being setup/shutdown.
-        return Int[x.id for x in PGRP.workers if isa(x, LocalProcess) || (x.state == W_CONNECTED)]
+        return Int[x.id for x in PGRP.workers if isa(x, LocalProcess) || (x.state === W_CONNECTED)]
     else
         return Int[x.id for x in PGRP.workers]
     end
@@ -911,7 +911,7 @@ end
 function id_in_procs(id)  # faster version of `id in procs()`
     if myid() == 1 || (PGRP.topology === :all_to_all  && !isclusterlazy())
         for x in PGRP.workers
-            if (x.id::Int) == id && (isa(x, LocalProcess) || (x::Worker).state == W_CONNECTED)
+            if (x.id::Int) == id && (isa(x, LocalProcess) || (x::Worker).state === W_CONNECTED)
                 return true
             end
         end
@@ -933,7 +933,7 @@ Specifically all workers bound to the same ip-address as `pid` are returned.
 """
 function procs(pid::Integer)
     if myid() == 1
-        all_workers = [x for x in PGRP.workers if isa(x, LocalProcess) || (x.state == W_CONNECTED)]
+        all_workers = [x for x in PGRP.workers if isa(x, LocalProcess) || (x.state === W_CONNECTED)]
         if (pid == 1) || (isa(map_pid_wrkr[pid].manager, LocalManager))
             Int[x.id for x in filter(w -> (w.id==1) || (isa(w.manager, LocalManager)), all_workers)]
         else
@@ -1040,11 +1040,11 @@ function _rmprocs(pids, waitfor)
 
         start = time_ns()
         while (time_ns() - start) < waitfor*1e9
-            all(w -> w.state == W_TERMINATED, rmprocset) && break
+            all(w -> w.state === W_TERMINATED, rmprocset) && break
             sleep(min(0.1, waitfor - (time_ns() - start)/1e9))
         end
 
-        unremoved = [wrkr.id for wrkr in filter(w -> w.state != W_TERMINATED, rmprocset)]
+        unremoved = [wrkr.id for wrkr in filter(w -> w.state !== W_TERMINATED, rmprocset)]
         if length(unremoved) > 0
             estr = string("rmprocs: pids ", unremoved, " not terminated after ", waitfor, " seconds.")
             throw(ErrorException(estr))
diff --git a/stdlib/Distributed/src/messages.jl b/stdlib/Distributed/src/messages.jl
index bbfb13f276fa5..4737f09d19efa 100644
--- a/stdlib/Distributed/src/messages.jl
+++ b/stdlib/Distributed/src/messages.jl
@@ -2,18 +2,6 @@
 
 abstract type AbstractMsg end
 
-const REF_ID = Ref(1)
-next_ref_id() = (id = REF_ID[]; REF_ID[] = id+1; id)
-
-struct RRID
-    whence::Int
-    id::Int
-
-    RRID() = RRID(myid(),next_ref_id())
-    RRID(whence, id) = new(whence,id)
-end
-hash(r::RRID, h::UInt) = hash(r.whence, hash(r.id, h))
-==(r::RRID, s::RRID) = (r.whence==s.whence && r.id==s.id)
 
 ## Wire format description
 #
diff --git a/stdlib/LibGit2/src/LibGit2.jl b/stdlib/LibGit2/src/LibGit2.jl
index 4bfde5a8ee3ac..50a39ca323aef 100644
--- a/stdlib/LibGit2/src/LibGit2.jl
+++ b/stdlib/LibGit2/src/LibGit2.jl
@@ -289,7 +289,7 @@ function fetch(repo::GitRepo; remote::AbstractString="origin",
         fo = FetchOptions(callbacks=remote_callbacks)
         fetch(rmt, refspecs, msg="from $(url(rmt))", options=fo)
     catch err
-        if isa(err, GitError) && err.code == Error.EAUTH
+        if isa(err, GitError) && err.code === Error.EAUTH
             reject(cred_payload)
         else
             Base.shred!(cred_payload)
@@ -345,7 +345,7 @@ function push(repo::GitRepo; remote::AbstractString="origin",
         push_opts = PushOptions(callbacks=remote_callbacks)
         push(rmt, refspecs, force=force, options=push_opts)
     catch err
-        if isa(err, GitError) && err.code == Error.EAUTH
+        if isa(err, GitError) && err.code === Error.EAUTH
             reject(cred_payload)
         else
             Base.shred!(cred_payload)
@@ -579,7 +579,7 @@ function clone(repo_url::AbstractString, repo_path::AbstractString;
         repo = try
             clone(repo_url, repo_path, clone_opts)
         catch err
-            if isa(err, GitError) && err.code == Error.EAUTH
+            if isa(err, GitError) && err.code === Error.EAUTH
                 reject(cred_payload)
             else
                 Base.shred!(cred_payload)
diff --git a/stdlib/LibGit2/src/rebase.jl b/stdlib/LibGit2/src/rebase.jl
index d24b2c23367a6..8151217b3950b 100644
--- a/stdlib/LibGit2/src/rebase.jl
+++ b/stdlib/LibGit2/src/rebase.jl
@@ -83,7 +83,7 @@ function commit(rb::GitRebase, sig::GitSignature)
                       oid_ptr, rb.ptr, C_NULL, sig.ptr, C_NULL, C_NULL)
     catch err
         # TODO: return current HEAD instead
-        err.code == Error.EAPPLIED && return nothing
+        err.code === Error.EAPPLIED && return nothing
         rethrow()
     end
     return oid_ptr[]
diff --git a/stdlib/REPL/src/REPLCompletions.jl b/stdlib/REPL/src/REPLCompletions.jl
index a16565bba3751..849a5ef4c977e 100644
--- a/stdlib/REPL/src/REPLCompletions.jl
+++ b/stdlib/REPL/src/REPLCompletions.jl
@@ -131,7 +131,9 @@ function complete_symbol(sym, ffunc, context_module=Main)::Vector{Completion}
         # We will exclude the results that the user does not want, as well
         # as excluding Main.Main.Main, etc., because that's most likely not what
         # the user wants
-        p = s->(!Base.isdeprecated(mod, s) && s != nameof(mod) && ffunc(mod, s))
+        p = let mod=mod, modname=nameof(mod)
+            s->(!Base.isdeprecated(mod, s) && s != modname && ffunc(mod, s))
+        end
         # Looking for a binding in a module
         if mod == context_module
             # Also look in modules we got through `using`
@@ -624,9 +626,9 @@ function completions(string, pos, context_module=Main)::Completions
         ex = Meta.parse(s * ")", raise=false, depwarn=false)
 
         if isa(ex, Expr)
-            if ex.head==:call
+            if ex.head === :call
                 return complete_methods(ex, context_module), first(frange):method_name_end, false
-            elseif ex.head==:. && ex.args[2] isa Expr && ex.args[2].head==:tuple
+            elseif ex.head === :. && ex.args[2] isa Expr && (ex.args[2]::Expr).head === :tuple
                 return complete_methods(ex, context_module), first(frange):(method_name_end - 1), false
             end
         end