improve some inferrabilities (#41495)

Author: aviatesk

base/errorshow.jl

@@ -222,7 +222,7 @@ function showerror(io::IO, ex::MethodError)
     arg_types = (is_arg_types ? ex.args : typesof(ex.args...))::DataType
     f = ex.f
     meth = methods_including_ambiguous(f, arg_types)
-    if length(meth) > 1
+    if isa(meth, MethodList) && length(meth) > 1
         return showerror_ambiguous(io, meth, f, arg_types)
     end
     arg_types_param::SimpleVector = arg_types.parameters
@@ -898,4 +898,3 @@ function show(io::IO, ::MIME"text/plain", stack::ExceptionStack)
     show_exception_stack(io, stack)
 end
 show(io::IO, stack::ExceptionStack) = show(io, MIME("text/plain"), stack)
-

base/process.jl

@@ -84,15 +84,16 @@ const SpawnIOs = Vector{Any} # convenience name for readability
         for io in stdio]
     handle = Libc.malloc(_sizeof_uv_process)
     disassociate_julia_struct(handle) # ensure that data field is set to C_NULL
+    (; exec, flags, env, dir) = cmd
     err = ccall(:jl_spawn, Int32,
               (Cstring, Ptr{Cstring}, Ptr{Cvoid}, Ptr{Cvoid},
                Ptr{Tuple{Cint, UInt}}, Int,
                UInt32, Ptr{Cstring}, Cstring, Ptr{Cvoid}),
-        file, cmd.exec, loop, handle,
+        file, exec, loop, handle,
         iohandles, length(iohandles),
-        cmd.flags,
-        cmd.env === nothing ? C_NULL : cmd.env,
-        isempty(cmd.dir) ? C_NULL : cmd.dir,
+        flags,
+        env === nothing ? C_NULL : env,
+        isempty(dir) ? C_NULL : dir,
         @cfunction(uv_return_spawn, Cvoid, (Ptr{Cvoid}, Int64, Int32)))
     if err != 0
         ccall(:jl_forceclose_uv, Cvoid, (Ptr{Cvoid},), handle) # will call free on handle eventually

base/toml_parser.jl

@@ -323,7 +323,7 @@ function Base.showerror(io::IO, err::ParserError)
     # In this case we want the arrow to point one character
     pos = err.pos::Int
     err.type == ErrUnexpectedEofExpectedValue && (pos += 1)
-    str1, err1 = point_to_line(err.str, pos, pos, io)
+    str1, err1 = point_to_line(err.str::String, pos, pos, io)
     @static if VERSION <= v"1.6.0-DEV.121"
         # See https://github.com/JuliaLang/julia/issues/36015
         format_fixer = get(io, :color, false) == true ? "\e[0m" : ""