diff --git a/internal/check/tree.go b/internal/check/tree.go
index 7ca2477..dc4e855 100644
--- a/internal/check/tree.go
+++ b/internal/check/tree.go
@@ -48,6 +48,13 @@ type scope struct {
 	variables map[string]types.Type
 }
 
+func (s *scope) child() *scope {
+	return &scope{
+		global:    s.global,
+		variables: maps.Clone(s.variables),
+	}
+}
+
 func (s *scope) checkNode(tree *parse.Tree, dot types.Type, node parse.Node) (types.Type, error) {
 	switch n := node.(type) {
 	case *parse.DotNode:
@@ -159,9 +166,14 @@ func (s *scope) checkIfNode(tree *parse.Tree, dot types.Type, n *parse.IfNode) e
 	if err != nil {
 		return err
 	}
-	if _, err := s.checkNode(tree, dot, n.List); err != nil {
+	if _, err := s.child().checkNode(tree, dot, n.List); err != nil {
 		return err
 	}
+	if n.ElseList != nil {
+		if _, err := s.child().checkNode(tree, dot, n.ElseList); err != nil {
+			return err
+		}
+	}
 	return nil
 }
 
@@ -238,7 +250,7 @@ func (s *scope) checkCommandNode(tree *parse.Tree, dot types.Type, n *parse.Comm
 			pt = sig.Params().At(i).Type()
 		}
 		if !types.AssignableTo(at, pt) {
-			return nil, fmt.Errorf("%s argument %d has type %s expected %s", n.Args[0], i-1, at, pt)
+			return nil, fmt.Errorf("%s argument %d has type %s expected %s", n.Args[0], i, at, pt)
 		}
 	}
 	return sig.Results().At(0).Type(), nil
@@ -286,11 +298,8 @@ func (s *scope) checkIdentifiers(tree *parse.Tree, dot types.Type, n parse.Node,
 }
 
 func (s *scope) checkRangeNode(tree *parse.Tree, dot types.Type, n *parse.RangeNode) error {
-	loopScope := &scope{
-		global:    s.global,
-		variables: maps.Clone(s.variables),
-	}
-	pipeType, err := loopScope.checkNode(tree, dot, n.Pipe)
+	child := s.child()
+	pipeType, err := child.checkNode(tree, dot, n.Pipe)
 	if err != nil {
 		return err
 	}
@@ -305,11 +314,11 @@ func (s *scope) checkRangeNode(tree *parse.Tree, dot types.Type, n *parse.RangeN
 	default:
 		return fmt.Errorf("failed to range over %s", pipeType)
 	}
-	if _, err := loopScope.checkNode(tree, x, n.List); err != nil {
+	if _, err := child.checkNode(tree, x, n.List); err != nil {
 		return err
 	}
 	if n.ElseList != nil {
-		if _, err := loopScope.checkNode(tree, x, n.ElseList); err != nil {
+		if _, err := child.checkNode(tree, x, n.ElseList); err != nil {
 			return err
 		}
 	}
diff --git a/internal/check/tree_test.go b/internal/check/tree_test.go
index d935d4e..9e85930 100644
--- a/internal/check/tree_test.go
+++ b/internal/check/tree_test.go
@@ -15,6 +15,7 @@ import (
 
 	"github.com/crhntr/muxt"
 	"github.com/crhntr/muxt/internal/check"
+	"github.com/crhntr/muxt/internal/source"
 )
 
 func TestTree(t *testing.T) {
@@ -278,14 +279,48 @@ func TestTree(t *testing.T) {
 			Template: `{{$v := 1}}{{.F $v}}`,
 			Data:     MethodWithIntParam{},
 		},
+		{
+			Name:     "when there is an error in the else block",
+			Template: `{{$x := "wrong type"}}{{if false}}{{else}}{{.F $x}}{{end}}`,
+			Data:     MethodWithIntParam{},
+			Error: func(t *testing.T, checkErr, _ error, tp types.Type) {
+				require.Error(t, checkErr)
+				require.ErrorContains(t, checkErr, ".F argument 0 has type untyped string expected int")
+			},
+		},
+		{
+			Name:     "variable redefined in if block",
+			Template: `{{$x := 1}}{{if true}}{{$x := "str"}}{{end}}{{.F $x}}`,
+			Data:     MethodWithIntParam{},
+		},
+		{
+			Name:     "range variable does not clobber outer scope",
+			Template: `{{$x := 1}}{{range .Numbers}}{{$x := "str"}}{{end}}{{square $x}}`,
+			Data:     MethodWithKeyValForSlices{},
+		},
+		{
+			Name:     "range variable does not override outer scope",
+			Template: `{{$x := "str"}}{{range $x, $y := .Numbers}}{{$.F $x $y}}{{end}}{{printf $x}}`,
+			Data:     MethodWithKeyValForSlices{},
+		},
+		{
+			Name:     "source provided function",
+			Template: `{{square 5}}`,
+			Data:     T{},
+		},
 	} {
 		t.Run(tt.Name, func(t *testing.T) {
-			templates, parseErr := template.New("template").Parse(tt.Template)
+			templates, parseErr := template.New("template").Funcs(template.FuncMap{
+				"square": square,
+			}).Parse(tt.Template)
 			require.NoError(t, parseErr)
 
 			dataType := checkTestPackage.Types.Scope().Lookup(reflect.TypeOf(tt.Data).Name()).Type()
 
-			if checkErr := check.Tree(templates.Tree, dataType, checkTestPackage.Types, checkTestPackage.Fset, newForrest(templates), nil); tt.Error != nil {
+			functions := source.DefaultFunctions(checkTestPackage.Types)
+			functions["square"] = checkTestPackage.Types.Scope().Lookup("square").(*types.Func).Signature()
+
+			if checkErr := check.Tree(templates.Tree, dataType, checkTestPackage.Types, checkTestPackage.Fset, newForrest(templates), functions); tt.Error != nil {
 				execErr := templates.Execute(io.Discard, tt.Data)
 				tt.Error(t, checkErr, execErr, dataType)
 			} else {
@@ -431,6 +466,10 @@ type MethodWithKeyValForMap struct {
 
 func (MethodWithKeyValForMap) F(int16, float32) (_ T) { return }
 
+func square(n int) int {
+	return n * n
+}
+
 func TestExampleTemplate(t *testing.T) {
 	packageList, loadErr := packages.Load(&packages.Config{
 		Mode:  packages.NeedName | packages.NeedFiles | packages.NeedDeps | packages.NeedTypes,
diff --git a/internal/source/template.go b/internal/source/template.go
index 8cc2808..05f379b 100644
--- a/internal/source/template.go
+++ b/internal/source/template.go
@@ -16,10 +16,8 @@ import (
 	"golang.org/x/tools/go/packages"
 )
 
-type TemplateFuncMap = map[string]*types.Signature
-
-func Templates(workingDirectory, templatesVariable string, pkg *packages.Package) (*template.Template, TemplateFuncMap, error) {
-	funcTypeMap := registerDefaultFunctions(pkg.Types)
+func Templates(workingDirectory, templatesVariable string, pkg *packages.Package) (*template.Template, Functions, error) {
+	funcTypeMap := DefaultFunctions(pkg.Types)
 	for _, tv := range IterateValueSpecs(pkg.Syntax) {
 		i := slices.IndexFunc(tv.Names, func(e *ast.Ident) bool {
 			return e.Name == templatesVariable
@@ -53,19 +51,7 @@ func findPackage(pkg *types.Package, path string) (*types.Package, bool) {
 	return nil, false
 }
 
-func registerDefaultFunctions(pkg *types.Package) TemplateFuncMap {
-	funcTypeMap := make(TemplateFuncMap)
-	fmtPkg, ok := findPackage(pkg, "fmt")
-	if !ok || fmtPkg == nil {
-		return funcTypeMap
-	}
-	funcTypeMap["printf"] = fmtPkg.Scope().Lookup("Sprintf").Type().(*types.Signature)
-	funcTypeMap["print"] = fmtPkg.Scope().Lookup("Sprint").Type().(*types.Signature)
-	funcTypeMap["println"] = fmtPkg.Scope().Lookup("Sprintln").Type().(*types.Signature)
-	return funcTypeMap
-}
-
-func evaluateTemplateSelector(ts *template.Template, pkg *types.Package, expression ast.Expr, workingDirectory, templatesVariable, templatePackageIdent, rDelim, lDelim string, fileSet *token.FileSet, files []*ast.File, embeddedPaths []string, funcTypeMaps TemplateFuncMap, fm template.FuncMap) (*template.Template, error) {
+func evaluateTemplateSelector(ts *template.Template, pkg *types.Package, expression ast.Expr, workingDirectory, templatesVariable, templatePackageIdent, rDelim, lDelim string, fileSet *token.FileSet, files []*ast.File, embeddedPaths []string, funcTypeMaps Functions, fm template.FuncMap) (*template.Template, error) {
 	call, ok := expression.(*ast.CallExpr)
 	if !ok {
 		return nil, contextError(workingDirectory, fileSet, expression.Pos(), fmt.Errorf("expected call expression"))
@@ -161,7 +147,7 @@ func evaluateTemplateSelector(ts *template.Template, pkg *types.Package, express
 	}
 }
 
-func evaluateFuncMap(workingDirectory, templatePackageIdent string, pkg *types.Package, fileSet *token.FileSet, call *ast.CallExpr, fm template.FuncMap, funcTypesMap TemplateFuncMap) error {
+func evaluateFuncMap(workingDirectory, templatePackageIdent string, pkg *types.Package, fileSet *token.FileSet, call *ast.CallExpr, fm template.FuncMap, funcTypesMap Functions) error {
 	const funcMapTypeIdent = "FuncMap"
 	if len(call.Args) != 1 {
 		return contextError(workingDirectory, fileSet, call.Lparen, fmt.Errorf("expected exactly 1 template.FuncMap composite literal argument"))
@@ -385,3 +371,30 @@ func relativeFilePaths(wd string, abs ...string) ([]string, error) {
 	}
 	return result, nil
 }
+
+type Functions map[string]*types.Signature
+
+func NewFunctions(m map[string]*types.Signature) Functions {
+	return Functions(m)
+}
+
+func DefaultFunctions(pkg *types.Package) Functions {
+	funcTypeMap := make(Functions)
+	fmtPkg, ok := findPackage(pkg, "fmt")
+	if !ok || fmtPkg == nil {
+		return funcTypeMap
+	}
+	funcTypeMap["printf"] = fmtPkg.Scope().Lookup("Sprintf").Type().(*types.Signature)
+	funcTypeMap["print"] = fmtPkg.Scope().Lookup("Sprint").Type().(*types.Signature)
+	funcTypeMap["println"] = fmtPkg.Scope().Lookup("Sprintln").Type().(*types.Signature)
+	return funcTypeMap
+}
+
+func (functions Functions) FindFunction(name string) (*types.Signature, bool) {
+	m := (map[string]*types.Signature)(functions)
+	fn, ok := m[name]
+	if !ok {
+		return nil, false
+	}
+	return fn, true
+}