Merge pull request #3041 from nspcc-dev/generic-decl

compiler: temporary disallow generics usages

docs/compiler.md

@@ -31,6 +31,8 @@ a dialect of Go rather than a complete port of the language:
  * type assertion with two return values is not supported; single return value (of the desired type)
    is supported; type assertion panics if value can't be asserted to the desired type, therefore
    it's up to the programmer whether assert can be performed successfully.
+ * type aliases including the built-in `any` alias are supported.
+ * generics are not supported, but eventually will be (at least, partially), ref. https://github.com/nspcc-dev/neo-go/issues/2376.
 
 ## VM API (interop layer)
 Compiler translates interop function calls into Neo VM syscalls or (for custom

pkg/compiler/analysis.go

@@ -19,6 +19,8 @@ var (
 	ErrMissingExportedParamName = errors.New("exported method is not allowed to have unnamed parameter")
 	// ErrInvalidExportedRetCount is returned when exported contract method has invalid return values count.
 	ErrInvalidExportedRetCount = errors.New("exported method is not allowed to have more than one return value")
+	// ErrGenericsUnsuppored is returned when generics-related tokens are encountered.
+	ErrGenericsUnsuppored = errors.New("generics are currently unsupported, please, see the https://github.com/nspcc-dev/neo-go/issues/2376")
 )
 
 var (
@@ -361,6 +363,13 @@ func (c *codegen) analyzeFuncAndGlobalVarUsage() funcUsage {
 			case *ast.FuncDecl:
 				name := c.getFuncNameFromDecl(pkgPath, n)
 
+				// filter out generic functions
+				err := c.checkGenericsFuncDecl(n, name)
+				if err != nil {
+					c.prog.Err = err
+					return false // Program is invalid.
+				}
+
 				// exported functions and methods are always assumed to be used
 				if isMain && n.Name.IsExported() || isInitFunc(n) || isDeployFunc(n) {
 					diff[name] = true
@@ -388,6 +397,13 @@ func (c *codegen) analyzeFuncAndGlobalVarUsage() funcUsage {
 				nodeCache[name] = declPair{n, c.importMap, pkgPath}
 				return false // will be processed in the next stage
 			case *ast.GenDecl:
+				// Filter out generics usage.
+				err := c.checkGenericsGenDecl(n, pkgPath)
+				if err != nil {
+					c.prog.Err = err
+					return false // Program is invalid.
+				}
+
 				// After skipping all funcDecls, we are sure that each value spec
 				// is a globally declared variable or constant. We need to gather global
 				// vars from both main and imported packages.
@@ -535,6 +551,54 @@ func (c *codegen) analyzeFuncAndGlobalVarUsage() funcUsage {
 	return usage
 }
 
+// checkGenericFuncDecl checks whether provided ast.FuncDecl has generic code.
+func (c *codegen) checkGenericsFuncDecl(n *ast.FuncDecl, funcName string) error {
+	var errGenerics error
+
+	// Generic function receiver.
+	if n.Recv != nil {
+		switch t := n.Recv.List[0].Type.(type) {
+		case *ast.StarExpr:
+			switch t.X.(type) {
+			case *ast.IndexExpr:
+				// func (x *Pointer[T]) Load() *T
+				errGenerics = errors.New("generic pointer function receiver")
+			}
+		case *ast.IndexExpr:
+			// func (x Structure[T]) Load() *T
+			errGenerics = errors.New("generic function receiver")
+		}
+	}
+
+	// Generic function parameters type: func SumInts[V int64 | int32](vals []V) V
+	if n.Type.TypeParams != nil {
+		errGenerics = errors.New("function type parameters")
+	}
+
+	if errGenerics != nil {
+		return fmt.Errorf("%w: %s has %s", ErrGenericsUnsuppored, funcName, errGenerics.Error())
+	}
+
+	return nil
+}
+
+// checkGenericsGenDecl checks whether provided ast.GenDecl has generic code.
+func (c *codegen) checkGenericsGenDecl(n *ast.GenDecl, pkgPath string) error {
+	// Generic type declaration:
+	// 	type List[T any] struct
+	// 	type List[T any] interface
+	if n.Tok == token.TYPE {
+		for _, s := range n.Specs {
+			typeSpec := s.(*ast.TypeSpec)
+			if typeSpec.TypeParams != nil {
+				return fmt.Errorf("%w: type %s is generic", ErrGenericsUnsuppored, c.getIdentName(pkgPath, typeSpec.Name.Name))
+			}
+		}
+	}
+
+	return nil
+}
+
 // nodeContext contains ast node with the corresponding import map, type info and package information
 // required to retrieve fully qualified node name (if so).
 type nodeContext struct {

pkg/compiler/codegen.go

@@ -566,6 +566,13 @@ func (c *codegen) Visit(node ast.Node) ast.Visitor {
 	//     x = 2
 	// )
 	case *ast.GenDecl:
+		// Filter out generics usage.
+		err := c.checkGenericsGenDecl(n, c.currPkg.PkgPath)
+		if err != nil {
+			c.prog.Err = err
+			return nil // Program is invalid.
+		}
+
 		if n.Tok == token.VAR || n.Tok == token.CONST {
 			c.saveSequencePoint(n)
 		}

pkg/compiler/func_scope.go

@@ -1,6 +1,7 @@
 package compiler
 
 import (
+	"fmt"
 	"go/ast"
 	"go/types"
 )
@@ -85,7 +86,23 @@ func (c *codegen) getFuncNameFromDecl(pkgPath string, decl *ast.FuncDecl) string
 		case *ast.Ident:
 			name = t.Name + "." + name
 		case *ast.StarExpr:
-			name = t.X.(*ast.Ident).Name + "." + name
+			switch t.X.(type) {
+			case *ast.Ident:
+				name = t.X.(*ast.Ident).Name + "." + name
+			case *ast.IndexExpr:
+				// Generic func declaration receiver: func (x *Pointer[T]) Load() *T
+				name = t.X.(*ast.IndexExpr).X.(*ast.Ident).Name + "." + name
+			default:
+				panic(fmt.Errorf("unexpected function `%s` receiver type: %T", name, t.X))
+			}
+		case *ast.IndexExpr:
+			switch t.X.(type) {
+			case *ast.Ident:
+				// Generic func declaration receiver: func (x Pointer[T]) Load() *T
+				name = t.X.(*ast.Ident).Name + "." + name
+			default:
+				panic(fmt.Errorf("unexpected function `%s` receiver type: %T", name, t.X))
+			}
 		}
 	}
 	return c.getIdentName(pkgPath, name)

pkg/compiler/generics_test.go

@@ -0,0 +1,91 @@
+package compiler_test
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/nspcc-dev/neo-go/pkg/compiler"
+	"github.com/stretchr/testify/require"
+)
+
+func TestGenericMethodReceiver(t *testing.T) {
+	t.Run("star expression", func(t *testing.T) {
+		src := `
+		package receiver
+		type Pointer[T any] struct {
+			value T
+		}
+		func (x *Pointer[T]) Load() *T {
+			return &x.value
+		}
+`
+		_, _, err := compiler.CompileWithOptions("foo.go", strings.NewReader(src), nil)
+		require.ErrorIs(t, err, compiler.ErrGenericsUnsuppored)
+	})
+	t.Run("ident expression", func(t *testing.T) {
+		src := `
+		package receiver
+		type Pointer[T any] struct {
+			value T
+		}
+		func (x Pointer[T]) Load() *T {
+			return &x.value
+		}
+`
+		_, _, err := compiler.CompileWithOptions("foo.go", strings.NewReader(src), nil)
+		require.ErrorIs(t, err, compiler.ErrGenericsUnsuppored)
+	})
+}
+
+func TestGenericFuncArgument(t *testing.T) {
+	src := `
+		package sum
+		func SumInts[V int64 | int32 | int16](vals []V) V { // doesn't make sense with NeoVM, but still it's a valid go code.
+			var s V
+			for i := range vals {
+				s += vals[i]
+			}
+			return s
+		}
+`
+	_, _, err := compiler.CompileWithOptions("foo.go", strings.NewReader(src), nil)
+	require.ErrorIs(t, err, compiler.ErrGenericsUnsuppored)
+}
+
+func TestGenericTypeDecl(t *testing.T) {
+	t.Run("global scope", func(t *testing.T) {
+		src := `
+		package sum
+		type List[T any] struct {
+			next *List[T]
+			val  T
+		}
+
+		func Main() any {
+			l := List[int]{}
+			return l
+		}
+`
+		_, _, err := compiler.CompileWithOptions("foo.go", strings.NewReader(src), nil)
+		require.ErrorIs(t, err, compiler.ErrGenericsUnsuppored)
+	})
+	t.Run("local scope", func(t *testing.T) {
+		src := `
+		package sum
+		func Main() any {
+			type (
+				SomeGoodType int
+			
+				List[T any] struct {
+					next *List[T]
+					val  T
+				}
+			)
+			l := List[int]{}
+			return l
+		}
+`
+		_, _, err := compiler.CompileWithOptions("foo.go", strings.NewReader(src), nil)
+		require.ErrorIs(t, err, compiler.ErrGenericsUnsuppored)
+	})
+}