feat(go): add UnsafeCast function

.github/workflows/main.yml

@@ -31,10 +31,10 @@ jobs:
         uses: actions/setup-dotnet@v1
         with:
           dotnet-version: '5.0.x'
-      - name: Set up Go 1.16
+      - name: Set up Go 1.17
         uses: actions/setup-go@v2
         with:
-          go-version: '1.16'
+          go-version: '1.17'
       - name: Set up Java 8
         uses: actions/setup-java@v2
         with:
@@ -125,10 +125,10 @@ jobs:
         uses: actions/setup-dotnet@v1
         with:
           dotnet-version: '5.0.x'
-      - name: Set up Go 1.16
+      - name: Set up Go 1.17
         uses: actions/setup-go@v2
         with:
-          go-version: '1.16'
+          go-version: '1.17'
       - name: Set up Java 8
         uses: actions/setup-java@v2
         with:
@@ -211,7 +211,7 @@ jobs:
       matrix:
         # All currently supported node versions (Maintenance LTS, Active LTS, Current)
         dotnet: ['3.1.x']
-        go: ['1.16']
+        go: ['1.17']
         java: ['8']
         node: ['12', '14', '16']
         os: [ubuntu-latest]
@@ -221,53 +221,53 @@ jobs:
           # Test using Windows
           - os: windows-latest
             dotnet: '3.1.x'
-            go: '1.16'
+            go: '1.17'
             java: '8'
             node: '12'
             python: '3.6'
           # Test using macOS
           - os: macos-latest
             dotnet: '3.1.x'
-            go: '1.16'
+            go: '1.17'
             java: '8'
             node: '12'
             python: '3.6'
           # Test alternate .NETs
           - java: '8'
             dotnet: '5.0.x'
-            go: '1.16'
+            go: '1.17'
             node: '12'
             os: ubuntu-latest
             python: '3.6'
           - java: '8'
             dotnet: '6.0.x'
-            go: '1.16'
+            go: '1.17'
             node: '12'
             os: ubuntu-latest
             python: '3.6'
           # Test alternate Javas
           - java: '11'
             dotnet: '3.1.x'
-            go: '1.16'
+            go: '1.17'
             node: '12'
             os: ubuntu-latest
             python: '3.6'
           # Test alternate Pythons
           - python: '3.7'
             dotnet: '3.1.x'
-            go: '1.16'
+            go: '1.17'
             java: '8'
             node: '12'
             os: ubuntu-latest
           - python: '3.8'
             dotnet: '3.1.x'
-            go: '1.16'
+            go: '1.17'
             java: '8'
             node: '12'
             os: ubuntu-latest
           - python: '3.9'
             dotnet: '3.1.x'
-            go: '1.16'
+            go: '1.17'
             java: '8'
             node: '12'
             os: ubuntu-latest

gh-pages/content/specification/6-compliance-report.md

@@ -5,7 +5,7 @@
 This section details the current state of each language binding with respect to our standard compliance suite.
 
 
-| number | test                                                                                                                                                             | java (99.16%) | golang (78.15%)                              | Dotnet | Python |
+| number | test                                                                                                                                                             | java (98.33%) | golang (78.33%)                              | Dotnet | Python |
 | ------ | ---------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------- | -------------------------------------------- | ------ | ------ |
 | 1      | asyncOverrides_overrideCallsSuper                                                                                                                                | 🟢            | [🔴](https://github.com/aws/jsii/issues/2670) | ⭕      | ⭕      |
 | 2      | [arrayReturnedByMethodCanBeRead]("Array created in the kernel can be queried for its elements")                                                                  | 🟢            | 🟢                                           | ⭕      | ⭕      |
@@ -126,3 +126,4 @@ This section details the current state of each language binding with respect to
 | 117    | testInterfaces                                                                                                                                                   | 🟢            | 🟢                                           | ⭕      | ⭕      |
 | 118    | [callbackParameterIsInterface]("Validates pure interfaces can be passed to callbacks")                                                                           | ⭕             | 🟢                                           | ⭕      | ⭕      |
 | 119    | [classCanBeUsedWhenNotExpressedlyLoaded]("Validates that types not explicitly loaded by the user can safely be returned by JS code")                             | 🟢            | 🟢                                           | ⭕      | ⭕      |
+| 120    | [downcasting]("Ensures unsafe-cast features work as expected")                                                                                                   | ⭕             | 🟢                                           | ⭕      | ⭕      |

packages/@jsii/go-runtime-test/project/compliance_test.go

@@ -1645,6 +1645,16 @@ func (suite *ComplianceSuite) TestClassCanBeUsedWhenNotExpressedlyLoaded() {
 	cdk16625.New().Test()
 }
 
+func (suite *ComplianceSuite) TestDownCasting() {
+	require := suite.Require()
+
+	anyValue := calc.SomeTypeJsii976_ReturnAnonymous()
+	var realValue calc.IReturnJsii976
+
+	jsii.UnsafeCast(anyValue, &realValue)
+
+	require.Equal(realValue.Foo(), jsii.Number(1337))
+}
 
 // required to make `go test` recognize the suite.
 func TestComplianceSuite(t *testing.T) {

packages/@jsii/go-runtime-test/project/go.mod

@@ -1,6 +1,6 @@
 module github.com/aws/jsii/go-runtime-test
 
-go 1.15
+go 1.17
 
 require (
 	github.com/aws/jsii-runtime-go v0.0.0
@@ -12,6 +12,17 @@ require (
 	golang.org/x/tools v0.1.0
 )
 
+require (
+	github.com/Masterminds/semver/v3 v3.1.1 // indirect
+	github.com/aws/jsii/jsii-calc/go/scopejsiicalcbaseofbase/v2 v2.1.1 // indirect
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	golang.org/x/mod v0.3.0 // indirect
+	golang.org/x/sys v0.0.0-20210119212857-b64e53b001e4 // indirect
+	golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 // indirect
+	gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b // indirect
+)
+
 replace (
 	github.com/aws/jsii-runtime-go => ../../go-runtime/jsii-runtime-go
 	github.com/aws/jsii/jsii-calc/go/jcb => ../jsii-calc/go/jcb

packages/@jsii/go-runtime-test/project/go.sum

@@ -1,7 +1,8 @@
 github.com/Masterminds/semver/v3 v3.1.1 h1:hLg3sBzpNErnxhQtUy/mmLR2I9foDujNK030IGemrRc=
 github.com/Masterminds/semver/v3 v3.1.1/go.mod h1:VPu/7SZ7ePZ3QOrcuXROw5FAcLl4a0cBrbBpGY/8hQs=
-github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
@@ -39,5 +40,6 @@ golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 h1:go1bK/D/BFZV2I8cIQd1N
 golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
-gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
+gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b h1:h8qDotaEPuJATrMmW04NCwg7v22aHH28wwpauUhK9Oo=
+gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

packages/@jsii/go-runtime-test/project/internal/cdk16625/cdk16625.go

@@ -11,7 +11,7 @@ func New() abc.Cdk16625 {
 	return c
 }
 
-type cdk16625 struct{
+type cdk16625 struct {
 	abc.Cdk16625
 }
 

packages/@jsii/go-runtime-test/project/tools.go

@@ -1,3 +1,4 @@
+//go:build tools
 // +build tools
 
 // Package tools contains the necessary statements to ensure tool dependencies

packages/@jsii/go-runtime/jsii-runtime-go/cast.go

@@ -0,0 +1,59 @@
+package jsii
+
+import (
+	"fmt"
+	"reflect"
+
+	"github.com/aws/jsii-runtime-go/internal/kernel"
+)
+
+// UnsafeCast converts the given interface value to the desired target interface
+// pointer. Panics if the from value is not a jsii proxy object, or if the to
+// value is not a pointer to an interface type.
+func UnsafeCast(from interface{}, into interface{}) {
+	rinto := reflect.ValueOf(into)
+	if rinto.Kind() != reflect.Ptr {
+		panic(fmt.Errorf("Second argument to UnsafeCast must be a pointer to an interface. Received %s", rinto.Type().String()))
+	}
+	rinto = rinto.Elem()
+	if rinto.Kind() != reflect.Interface {
+		panic(fmt.Errorf("Second argument to UnsafeCast must be a pointer to an interface. Received pointer to %s", rinto.Type().String()))
+	}
+
+	rfrom := reflect.ValueOf(from)
+
+	// If rfrom is essentially nil, set into to nil and return.
+	if !rfrom.IsValid() || rfrom.IsZero() {
+		null := reflect.Zero(rinto.Type())
+		rinto.Set(null)
+		return
+	}
+	// Interfaces may present as a pointer to an implementing struct, and that's fine...
+	if rfrom.Kind() != reflect.Interface && rfrom.Kind() != reflect.Ptr {
+		panic(fmt.Errorf("First argument to UnsafeCast must be an interface value. Received %s", rfrom.Type().String()))
+	}
+
+	// If rfrom can be directly converted to rinto, just do it.
+	if rfrom.CanConvert(rinto.Type()) {
+		rfrom = rfrom.Convert(rinto.Type())
+		rinto.Set(rfrom)
+		return
+	}
+
+	client := kernel.GetClient()
+	if objID, found := client.FindObjectRef(rfrom); found {
+		// Ensures the value is initialized properly. Panics if the target value is not a jsii interface type.
+		client.Types().InitJsiiProxy(rinto)
+
+		// If the target type is a behavioral interface, add it to the ObjectRef.Interfaces list.
+		if fqn, found := client.Types().InterfaceFQN(rinto.Type()); found {
+			objID.Interfaces = append(objID.Interfaces, fqn)
+		}
+
+		// Make the new value an alias to the old value.
+		client.RegisterInstance(rinto, objID)
+		return
+	}
+
+	panic(fmt.Errorf("First argument to UnsafeCast must be a jsii proxy value. Received %s", rfrom.String()))
+}

packages/@jsii/go-runtime/jsii-runtime-go/cast_test.go

@@ -0,0 +1,101 @@
+package jsii
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/aws/jsii-runtime-go/internal/api"
+	"github.com/aws/jsii-runtime-go/internal/kernel"
+)
+
+type MockInterfaceABase interface {
+	MockMethodABase(_ float64)
+}
+
+type mockABase struct {
+	_ int // padding
+}
+
+func (m *mockABase) MockMethodABase(_ float64) {}
+
+type MockInterfaceA interface {
+	MockInterfaceABase
+	MockMethodA(_ string)
+}
+
+func NewMockInterfaceA() MockInterfaceA {
+	return &mockA{mockABase{}}
+}
+
+type mockA struct {
+	mockABase
+}
+
+func (m *mockA) MockMethodA(_ string) {}
+
+type MockInterfaceB interface {
+	MockMethodB(_ int)
+}
+
+func NewMockInterfaceB() MockInterfaceB {
+	return &mockB{}
+}
+
+type mockB struct {
+	_ int // Padding
+}
+
+func (m *mockB) MockMethodB(_ int) {}
+
+func TestNilSource(t *testing.T) {
+	// Make "into" not nil to ensure the cast function overwrites it.
+	into := NewMockInterfaceB()
+	UnsafeCast(nil, &into)
+
+	if into != nil {
+		t.Fail()
+	}
+}
+
+func TestSourceAndTargetAreTheSame(t *testing.T) {
+	into := NewMockInterfaceB()
+	original := into
+	UnsafeCast(into, &into)
+
+	if into != original {
+		t.Fail()
+	}
+}
+
+func TestTargetIsSubclassOfSource(t *testing.T) {
+	from := NewMockInterfaceA()
+	var into MockInterfaceABase
+	UnsafeCast(from, &into)
+
+	if into != from {
+		t.Fail()
+	}
+}
+
+func TestRegistersAlias(t *testing.T) {
+	client := kernel.GetClient()
+
+	objid := api.ObjectRef{InstanceID: "Object@1337#42"}
+	from := NewMockInterfaceA()
+	client.RegisterInstance(reflect.ValueOf(from), objid)
+
+	var into MockInterfaceB
+	client.Types().RegisterInterface(api.FQN("mock.InterfaceB"), reflect.TypeOf(&into).Elem(), []api.Override{}, func() interface{} { return NewMockInterfaceB() })
+
+	UnsafeCast(from, &into)
+
+	if into == nil {
+		t.Fail()
+	}
+
+	if refid, found := client.FindObjectRef(reflect.ValueOf(into)); !found {
+		t.Fail()
+	} else if refid.InstanceID != objid.InstanceID {
+		t.Fail()
+	}
+}

packages/@jsii/go-runtime/jsii-runtime-go/go.mod

@@ -1,10 +1,16 @@
 module github.com/aws/jsii-runtime-go
 
-go 1.16
+go 1.17
 
 require (
 	github.com/Masterminds/semver/v3 v3.1.1
 	github.com/stretchr/testify v1.7.0
 )
 
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b // indirect
+)
+
 retract v1.27.0

packages/@jsii/go-runtime/jsii-runtime-go/go.sum

@@ -1,14 +1,15 @@
 github.com/Masterminds/semver/v3 v3.1.1 h1:hLg3sBzpNErnxhQtUy/mmLR2I9foDujNK030IGemrRc=
 github.com/Masterminds/semver/v3 v3.1.1/go.mod h1:VPu/7SZ7ePZ3QOrcuXROw5FAcLl4a0cBrbBpGY/8hQs=
-github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
-github.com/stretchr/objx v0.1.0 h1:4G4v2dO3VZwixGIRoQ5Lfboy6nUhCyYzaqnIAPPhYs4=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/testify v1.7.0 h1:nwc3DEeHmmLAfoZucVR881uASk0Mfjw8xYJ99tb5CcY=
 github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
-gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
+gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b h1:h8qDotaEPuJATrMmW04NCwg7v22aHH28wwpauUhK9Oo=
+gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=