Because no versions of macros match >=0.1.0-main.0 <0.1.0-main.0 and macros >=0.1.0-main.0 <0.1.0-main.1 depends on _macros 0.1.0 from sdk, macros >=0.1.0-main.0 <0.1.0-main.1 requires _macros 0.1.0 from sdk.
And because no versions of _macros from sdk match 0.1.0, macros >=0.1.0-main.0 <0.1.0-main.1 is forbidden.
And because macros >=0.1.0-main.1 <0.1.0-main.2 depends on _macros 0.1.1 from sdk which doesn't match any versions, macros >=0.1.0-main.0 <0.1.0-main.2 is forbidden.
And because macros >=0.1.0-main.2 <0.1.0-main.3 depends on _macros 0.1.2 from sdk which doesn't match any versions, macros >=0.1.0-main.0 <0.1.0-main.3 is forbidden.
And because macros >=0.1.0-main.3 <0.1.0-main.4 depends on _macros 0.1.3 from sdk which doesn't match any versions, macros >=0.1.0-main.0 <0.1.0-main.4 is forbidden.
And because macros >=0.1.0-main.4 <0.1.0-main.5 depends on _macros 0.1.4 from sdk which doesn't match any versions, macros >=0.1.0-main.0 <0.1.0-main.5 is forbidden.
And because macros >=0.1.0-main.5 <0.1.0-main.6 depends on _macros 0.1.5 from sdk which doesn't match any versions, macros >=0.1.0-main.0 <0.1.0-main.6 is forbidden.
And because analyzer >=6.5.0 depends on macros >=0.1.0-main.0 <0.1.1 and macros >=0.1.0-main.6 depends on _macros 0.1.6 from sdk, analyzer >=6.5.0 requires _macros 0.1.6 from sdk.
So, because no versions of _macros from sdk match 0.1.6 and flutter_tools depends on analyzer 6.5.0, version solving failed.
Error: Unable to 'pub upgrade' flutter tool. Retrying in five seconds... (9 tries left)