consider inherited interfaces when checking for member clashes in int…

…ersection types

runtime/sema/checker.go

@@ -937,40 +937,45 @@ func CheckIntersectionType(
 
 		// The intersections may not have clashing members
 
-		// TODO: also include interface conformances' members
-		//   once interfaces can have conformances
+		checkClashingMember := func(interfaceType *InterfaceType) {
+			interfaceType.Members.Foreach(func(name string, member *Member) {
 
-		interfaceType.Members.Foreach(func(name string, member *Member) {
-			if previousDeclaringInterfaceType, ok := memberSet[name]; ok {
+				if previousDeclaringInterfaceType, ok := memberSet[name]; ok {
 
-				// If there is an overlap in members, ensure the members have the same type
+					// If there is an overlap in members, ensure the members have the same type
 
-				memberType := member.TypeAnnotation.Type
+					memberType := member.TypeAnnotation.Type
 
-				prevMemberType, ok := previousDeclaringInterfaceType.Members.Get(name)
-				if !ok {
-					panic(errors.NewUnreachableError())
-				}
+					prevMemberType, ok := previousDeclaringInterfaceType.Members.Get(name)
+					if !ok {
+						panic(errors.NewUnreachableError())
+					}
 
-				previousMemberType := prevMemberType.TypeAnnotation.Type
+					previousMemberType := prevMemberType.TypeAnnotation.Type
 
-				if !memberType.IsInvalidType() &&
-					!previousMemberType.IsInvalidType() &&
-					!memberType.Equal(previousMemberType) {
+					if !memberType.IsInvalidType() &&
+						!previousMemberType.IsInvalidType() &&
+						!memberType.Equal(previousMemberType) {
 
-					report(func(t *ast.IntersectionType) error {
-						return &IntersectionMemberClashError{
-							Name:                  name,
-							RedeclaringType:       interfaceType,
-							OriginalDeclaringType: previousDeclaringInterfaceType,
-							Range:                 ast.NewRangeFromPositioned(memoryGauge, t.Types[i]),
-						}
-					})
+						report(func(t *ast.IntersectionType) error {
+							return &IntersectionMemberClashError{
+								Name:                  name,
+								RedeclaringType:       interfaceType,
+								OriginalDeclaringType: previousDeclaringInterfaceType,
+								Range:                 ast.NewRangeFromPositioned(memoryGauge, t.Types[i]),
+							}
+						})
+					}
+				} else {
+					memberSet[name] = interfaceType
 				}
-			} else {
-				memberSet[name] = interfaceType
-			}
-		})
+			})
+		}
+
+		checkClashingMember(interfaceType)
+
+		interfaceType.EffectiveInterfaceConformanceSet().
+			ForEach(checkClashingMember)
 	}
 
 	// If no intersection type is given, infer `AnyResource`/`AnyStruct`

runtime/tests/checker/intersection_test.go

@@ -19,6 +19,7 @@
 package checker
 
 import (
+	"fmt"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -442,6 +443,97 @@ func TestCheckIntersectionTypeMemberAccess(t *testing.T) {
 	})
 }
 
+func TestCheckIntersectionTypeWithInheritanceMemberClash(t *testing.T) {
+
+	t.Parallel()
+
+	const firstMember = `let n: Int`
+	const secondMember = `let n: Bool`
+
+	test := func(
+		memberInA, memberInC bool,
+		firstType, secondType string,
+	) {
+
+		testName := fmt.Sprintf(
+			"memberInA: %v, memberInC: %v, firstType: %s, secondType: %s",
+			memberInA, memberInC, firstType, secondType,
+		)
+
+		t.Run(testName, func(t *testing.T) {
+			t.Parallel()
+
+			bodyA := ""
+			bodyB := ""
+			bodyC := ""
+			bodyD := ""
+
+			if memberInA {
+				bodyA = firstMember
+			} else {
+				bodyB = firstMember
+			}
+
+			if memberInC {
+				bodyC = secondMember
+			} else {
+				bodyD = secondMember
+			}
+
+			_, err := ParseAndCheck(t,
+				fmt.Sprintf(
+					`
+				      struct interface A {
+                          %s
+                      }
+
+                      struct interface B: A {
+                          %s
+                      }
+
+                      struct interface C {
+                          %s
+                      }
+
+                      struct interface D: C {
+                          %s
+                      }
+
+                      fun test(_ v: {%s, %s}) {}
+				    `,
+					bodyA,
+					bodyB,
+					bodyC,
+					bodyD,
+					firstType,
+					secondType,
+				),
+			)
+
+			errs := RequireCheckerErrors(t, err, 1)
+
+			assert.IsType(t, &sema.IntersectionMemberClashError{}, errs[0])
+		})
+	}
+
+	for _, memberInA := range []bool{true, false} {
+		for _, memberInC := range []bool{true, false} {
+			for _, firstType := range []string{"A", "B"} {
+				for _, secondType := range []string{"C", "D"} {
+
+					if (firstType == "A" && !memberInA) ||
+						(secondType == "C" && !memberInC) {
+
+						continue
+					}
+
+					test(memberInA, memberInC, firstType, secondType)
+				}
+			}
+		}
+	}
+}
+
 func TestCheckIntersectionTypeSubtyping(t *testing.T) {
 
 	t.Parallel()