compiler: use fully-qualified names for tracking functions

Function name now consists of 3 parts:
1) full package path
2) method receiver type (if any)
3) function name itself .

Fix #1150.

Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>

pkg/compiler/analysis.go

@@ -113,14 +113,15 @@ func (c *codegen) analyzeFuncUsage() funcUsage {
 			case *ast.CallExpr:
 				switch t := n.Fun.(type) {
 				case *ast.Ident:
-					usage[t.Name] = true
+					usage[c.getIdentName("", t.Name)] = true
 				case *ast.SelectorExpr:
-					usage[t.Sel.Name] = true
+					name, _ := c.getFuncNameFromSelector(t)
+					usage[name] = true
 				}
 			case *ast.FuncDecl:
 				// exported functions are always assumed to be used
 				if isMain && n.Name.IsExported() {
-					usage[n.Name.Name] = true
+					usage[c.getFuncNameFromDecl(pkg.Path(), n)] = true
 				}
 			}
 			return true

pkg/compiler/codegen.go

@@ -68,6 +68,9 @@ type codegen struct {
 	// constMap contains constants from foreign packages.
 	constMap map[string]types.TypeAndValue
 
+	// currPkg is current package being processed.
+	currPkg *types.Package
+
 	// mainPkg is a main package metadata.
 	mainPkg *loader.PackageInfo
 
@@ -278,19 +281,18 @@ func (c *codegen) convertFuncDecl(file ast.Node, decl *ast.FuncDecl, pkg *types.
 		ok, isLambda bool
 	)
 
-	f, ok = c.funcs[decl.Name.Name]
+	f, ok = c.funcs[c.getFuncNameFromDecl("", decl)]
 	if ok {
 		// If this function is a syscall or builtin we will not convert it to bytecode.
 		if isSyscall(f) || isCustomBuiltin(f) {
 			return
 		}
 		c.setLabel(f.label)
-	} else if f, ok = c.lambda[decl.Name.Name]; ok {
+	} else if f, ok = c.lambda[c.getIdentName("", decl.Name.Name)]; ok {
 		isLambda = ok
 		c.setLabel(f.label)
 	} else {
 		f = c.newFunc(decl)
-		f.pkg = pkg
 	}
 
 	f.rng.Start = uint16(c.prog.Len())
@@ -738,7 +740,7 @@ func (c *codegen) Visit(node ast.Node) ast.Visitor {
 
 		switch fun := n.Fun.(type) {
 		case *ast.Ident:
-			f, ok = c.funcs[fun.Name]
+			f, ok = c.funcs[c.getIdentName("", fun.Name)]
 			isBuiltin = isGoBuiltin(fun.Name)
 			if !ok && !isBuiltin {
 				name = fun.Name
@@ -751,13 +753,14 @@ func (c *codegen) Visit(node ast.Node) ast.Visitor {
 			// If this is a method call we need to walk the AST to load the struct locally.
 			// Otherwise this is a function call from a imported package and we can call it
 			// directly.
-			if c.typeInfo.Selections[fun] != nil {
+			name, isMethod := c.getFuncNameFromSelector(fun)
+			if isMethod {
 				ast.Walk(c, fun.X)
 				// Dont forget to add 1 extra argument when its a method.
 				numArgs++
 			}
 
-			f, ok = c.funcs[fun.Sel.Name]
+			f, ok = c.funcs[name]
 			// @FIXME this could cause runtime errors.
 			f.selector = fun.X.(*ast.Ident)
 			if !ok {
@@ -1431,18 +1434,30 @@ func (c *codegen) convertToken(tok token.Token) {
 }
 
 func (c *codegen) newFunc(decl *ast.FuncDecl) *funcScope {
-	f := newFuncScope(decl, c.newLabel())
-	c.funcs[f.name] = f
+	f := c.newFuncScope(decl, c.newLabel())
+	c.funcs[c.getFuncNameFromDecl("", decl)] = f
 	return f
 }
 
+// getFuncNameFromSelector returns fully-qualified function name from the selector expression.
+// Second return value is true iff this was a method call, not foreign package call.
+func (c *codegen) getFuncNameFromSelector(e *ast.SelectorExpr) (string, bool) {
+	ident := e.X.(*ast.Ident)
+	if c.typeInfo.Selections[e] != nil {
+		typ := c.typeInfo.Types[ident].Type.String()
+		return c.getIdentName(typ, e.Sel.Name), true
+	}
+	return c.getIdentName(ident.Name, e.Sel.Name), false
+}
+
 func (c *codegen) newLambda(u uint16, lit *ast.FuncLit) {
 	name := fmt.Sprintf("lambda@%d", u)
-	c.lambda[name] = newFuncScope(&ast.FuncDecl{
+	f := c.newFuncScope(&ast.FuncDecl{
 		Name: ast.NewIdent(name),
 		Type: lit.Type,
 		Body: lit.Body,
 	}, u)
+	c.lambda[c.getFuncNameFromDecl("", f.decl)] = f
 }
 
 func (c *codegen) compile(info *buildInfo, pkg *loader.PackageInfo) error {
@@ -1472,7 +1487,8 @@ func (c *codegen) compile(info *buildInfo, pkg *loader.PackageInfo) error {
 			case *ast.FuncDecl:
 				// Don't convert the function if it's not used. This will save a lot
 				// of bytecode space.
-				if funUsage.funcUsed(n.Name.Name) {
+				name := c.getFuncNameFromDecl(pkg.Path(), n)
+				if funUsage.funcUsed(name) && !isInteropPath(pkg.Path()) {
 					c.convertFuncDecl(f, n, pkg)
 				}
 			}
@@ -1519,7 +1535,6 @@ func (c *codegen) resolveFuncDecls(f *ast.File, pkg *types.Package) {
 		switch n := decl.(type) {
 		case *ast.FuncDecl:
 			c.newFunc(n)
-			c.funcs[n.Name.Name].pkg = pkg
 		}
 	}
 }

pkg/compiler/compiler.go

@@ -48,6 +48,7 @@ type buildInfo struct {
 func (c *codegen) ForEachFile(fn func(*ast.File, *types.Package)) {
 	for _, pkg := range c.buildInfo.program.AllPackages {
 		c.typeInfo = &pkg.Info
+		c.currPkg = pkg.Pkg
 		for _, f := range pkg.Files {
 			c.fillImportMap(f, pkg.Pkg)
 			fn(f, pkg.Pkg)

pkg/compiler/debug.go

@@ -152,6 +152,8 @@ func (c *codegen) methodInfoFromScope(name string, scope *funcScope) *MethodDebu
 			})
 		}
 	}
+	ss := strings.Split(name, ".")
+	name = ss[len(ss)-1]
 	return &MethodDebugInfo{
 		ID: name,
 		Name: DebugMethodName{

pkg/compiler/func_scope.go

@@ -45,7 +45,7 @@ type funcScope struct {
 	i int
 }
 
-func newFuncScope(decl *ast.FuncDecl, label uint16) *funcScope {
+func (c *codegen) newFuncScope(decl *ast.FuncDecl, label uint16) *funcScope {
 	var name string
 	if decl.Name != nil {
 		name = decl.Name.Name
@@ -54,6 +54,7 @@ func newFuncScope(decl *ast.FuncDecl, label uint16) *funcScope {
 		name:      name,
 		decl:      decl,
 		label:     label,
+		pkg:       c.currPkg,
 		vars:      newVarScope(),
 		voidCalls: map[*ast.CallExpr]bool{},
 		variables: []string{},
@@ -61,6 +62,14 @@ func newFuncScope(decl *ast.FuncDecl, label uint16) *funcScope {
 	}
 }
 
+func (c *codegen) getFuncNameFromDecl(pkgPath string, decl *ast.FuncDecl) string {
+	name := decl.Name.Name
+	if decl.Recv != nil {
+		name = decl.Recv.List[0].Type.(*ast.Ident).Name + "." + name
+	}
+	return c.getIdentName(pkgPath, name)
+}
+
 // analyzeVoidCalls checks for functions that are not assigned
 // and therefore we need to cleanup the return value from the stack.
 func (c *funcScope) analyzeVoidCalls(node ast.Node) bool {

pkg/compiler/global_test.go

@@ -196,3 +196,33 @@ func TestExportedConst(t *testing.T) {
 	}`
 	eval(t, src, big.NewInt(42))
 }
+
+func TestMultipleFuncSameName(t *testing.T) {
+	t.Run("Simple", func(t *testing.T) {
+		src := `package foo
+		import "github.com/nspcc-dev/neo-go/pkg/compiler/testdata/multi"
+		func Main() int {
+			return multi.Sum() + Sum()
+		}
+		func Sum() int {
+			return 11
+		}`
+		eval(t, src, big.NewInt(53))
+	})
+	t.Run("WithMethod", func(t *testing.T) {
+		src := `package foo
+		import "github.com/nspcc-dev/neo-go/pkg/compiler/testdata/foo"
+		type Foo struct{}
+		func (f Foo) Bar() int { return 11 }
+		func Bar() int { return 22 }
+		func Main() int {
+			var a Foo
+			var b foo.Foo
+			return a.Bar() + // 11
+				foo.Bar() +  // 1
+				b.Bar() +    // 8
+				Bar()        // 22
+		}`
+		eval(t, src, big.NewInt(42))
+	})
+}

pkg/compiler/testdata/foo/foo.go

@@ -4,3 +4,16 @@ package foo
 func NewBar() int {
 	return 10
 }
+
+// Foo is a type.
+type Foo struct{}
+
+// Bar is a function.
+func Bar() int {
+	return 1
+}
+
+// Bar is a method.
+func (f Foo) Bar() int {
+	return 8
+}

pkg/compiler/vm_test.go

@@ -74,6 +74,7 @@ func vmAndCompileInterop(t *testing.T, src string) (*vm.VM, *storagePlugin) {
 
 	b, di, err := compiler.CompileWithDebugInfo(strings.NewReader(src))
 	require.NoError(t, err)
+
 	invokeMethod(t, testMainIdent, b, vm, di)
 	return vm, storePlugin
 }