Analyzer: no static type warning when multiple implemented interfaces have conflicting members

[DartBot]

This issue was originally filed by [email protected]

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This is a duplicate of issue #3306 which was wrongfully closed

According to spec (8.1.1):
"if there are multiple members m1, …, mk with the same name n that would be inherited (because identically named members existed in several superinterfaces) then at most one member is inherited. If the static types T1, …, Tk of the members m1, …, mk are not identical, then there must be a member mx such that Tx <: Ti, 1 <= x <= k for all i, 1 <= i <= k, or a static type warning occurs."
the following should result in a static type warning:

abstract class SI1 {
  int foo;
}

abstract class SI2 {
  String foo;
}

abstract class I implements SI1, SI2 {}

However, there's currently none

co19 tests expecting this warning:
Language/08_Interfaces/4_Superinterfaces/1_Inheritance_and_Overriding_A02_t01-t04

[iposva-google]

Added Area-Analyzer, Triaged labels.

[bwilkerson]

Added this to the M3 milestone.

[bwilkerson]

Removed this from the M3 milestone.
Added this to the M4 milestone.

[bwilkerson]

Removed this from the M4 milestone.
Added this to the M5 milestone.

[bwilkerson]

Set owner to @jwren.

[jwren]

Fixed and confirmed in svn version 23492

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Added Fixed label.