fmt: fix removal of selective imported types used as type parameter (#12431)

vlib/v/fmt/fmt.v

@@ -251,6 +251,11 @@ pub fn (mut f Fmt) mark_types_import_as_used(typ ast.Type) {
 		f.mark_types_import_as_used(map_info.value_type)
 		return
 	}
+	if sym.info is ast.GenericInst {
+		for concrete_typ in sym.info.concrete_types {
+			f.mark_types_import_as_used(concrete_typ)
+		}
+	}
 	name := sym.name.split('<')[0] // take `Type` from `Type<T>`
 	f.mark_import_as_used(name)
 }

vlib/v/fmt/tests/import_selective_expected.vv

@@ -9,8 +9,12 @@ import mod {
 	Enum,
 	FnArg,
 	FnArgGeneric,
+	FnArgTypeParam1,
+	FnArgTypeParam2,
 	FnRet,
 	FnRetGeneric,
+	FnRetTypeParam1,
+	FnRetTypeParam2,
 	InterfaceField,
 	InterfaceMethodArg,
 	InterfaceMethodRet,
@@ -57,6 +61,8 @@ fn f(v FnArg) FnRet {
 	return FnRet{}
 }
 
+fn f2(v Generic<FnArgTypeParam1, FnArgTypeParam2>) Generic<FnRetTypeParam1, FnRetTypeParam2> {}
+
 fn f_generic<T>(v FnArgGeneric<T>) FnRetGeneric<T> {
 	return FnRetGeneric<T>{}
 }

vlib/v/fmt/tests/import_selective_input.vv

@@ -22,8 +22,12 @@ import mod {
 
 	FnArg,
 	FnArgGeneric
+	FnArgTypeParam1
+	FnArgTypeParam2
 	FnRet,
 	FnRetGeneric
+	FnRetTypeParam1,
+	FnRetTypeParam2,
 
 	RightOfIs,
 	RightOfAs,
@@ -60,6 +64,8 @@ fn f(v FnArg) FnRet {
 	return FnRet{}
 }
 
+fn f2(v Generic<FnArgTypeParam1, FnArgTypeParam2>) Generic<FnRetTypeParam1, FnRetTypeParam2> {}
+
 fn f_generic<T>(v FnArgGeneric<T>) FnRetGeneric<T> {
 	return FnRetGeneric<T>{}
 }