Add tests for interface implementation across aliasing

Author: smowton

go/ql/test/library-tests/semmle/go/aliases/InterfaceImpls/test.expected

@@ -0,0 +1,13 @@
+callTargets
+| test.go:38:2:38:24 | call to ImplementMe | test.go:12:1:12:72 | function declaration | ImplementMe |
+| test.go:38:2:38:24 | call to ImplementMe | test.go:17:1:17:67 | function declaration | ImplementMe |
+| test.go:38:2:38:24 | call to ImplementMe | test.go:23:1:23:54 | function declaration | ImplementMe |
+| test.go:38:2:38:24 | call to ImplementMe | test.go:29:1:29:61 | function declaration | ImplementMe |
+| test.go:38:2:38:24 | call to ImplementMe | test.go:35:1:35:74 | function declaration | ImplementMe |
+#select
+| file://:0:0:0:0 | basic interface type | file://:0:0:0:0 | basic interface type |
+| file://:0:0:0:0 | basic interface type | test.go:10:6:10:10 | Impl1 |
+| file://:0:0:0:0 | basic interface type | test.go:15:6:15:10 | Impl2 |
+| file://:0:0:0:0 | basic interface type | test.go:20:6:20:10 | Impl3 |
+| file://:0:0:0:0 | basic interface type | test.go:26:6:26:10 | Impl4 |
+| file://:0:0:0:0 | basic interface type | test.go:32:6:32:10 | Impl5 |

go/ql/test/library-tests/semmle/go/aliases/InterfaceImpls/test.go

@@ -0,0 +1,39 @@
+package intfs
+
+type IntAlias = int
+
+type Target = interface {
+	ImplementMe(callable func (struct { x IntAlias }))
+}
+
+// Simple direct implementation
+type Impl1 struct {}
+
+func (recv Impl1) ImplementMe(callable func (struct { x IntAlias })) { }
+
+// Implementation via unalising
+type Impl2 struct {}
+
+func (recv Impl2) ImplementMe(callable func (struct { x int })) { }
+
+// Implementation via top-level aliasing
+type Impl3 struct {}
+
+type Impl3Alias = func (struct { x IntAlias })
+func (recv Impl3) ImplementMe(callable Impl3Alias) { }
+
+// Implementation via aliasing the struct
+type Impl4 struct {}
+
+type Impl4Alias = struct { x IntAlias }
+func (recv Impl4) ImplementMe(callable func (Impl4Alias)) { }
+
+// Implementation via aliasing the struct member
+type Impl5 struct {}
+
+type Impl5Alias = IntAlias 
+func (recv Impl5) ImplementMe(callable func (struct { x Impl5Alias })) { }
+
+func Caller(target Target) {
+	target.ImplementMe(nil)
+}

go/ql/test/library-tests/semmle/go/aliases/InterfaceImpls/test.ql

@@ -0,0 +1,10 @@
+import go
+
+query predicate callTargets(DataFlow::CallNode cn, FuncDef target, string targetName) {
+  target = cn.getACallee() and targetName = target.getName()
+}
+
+from InterfaceType i, Type impl
+where i.hasMethod("ImplementMe", _)
+and impl.implements(i)
+select i, impl