ast/astutil: use more generics to reduce duplication

Now all lists are handled consistently as well.

Signed-off-by: Daniel Martí <mvdan@mvdan.cc>
Change-Id: I4c5f0759e4bcdd516340fc968777ce60a1da6392
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1194007
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>
Unity-Result: CUE porcuepine <cue.porcuepine@gmail.com>
Reviewed-by: Roger Peppe <rogpeppe@gmail.com>

cue/ast/astutil/apply.go

@@ -199,19 +199,6 @@ type applyVisitor interface {
 
 // Helper functions for common node lists. They may be empty.
 
-func applyExprList(v applyVisitor, parent Cursor, list []ast.Expr) {
-	c := newCursor(parent, nil, nil)
-	for i, x := range list {
-		c.index = i
-		c.node = x
-		c.typ = &list[i]
-		applyCursor(v, c)
-		if x != c.node {
-			list[i] = c.node.(ast.Expr)
-		}
-	}
-}
-
 type declsCursor struct {
 	*cursor
 	decls, after, process []ast.Decl
@@ -295,6 +282,19 @@ func apply[N ast.Node](v applyVisitor, parent Cursor, nodePtr *N) {
 	}
 }
 
+func applyList[N ast.Node](v applyVisitor, parent Cursor, list []N) {
+	c := newCursor(parent, nil, nil)
+	for i, node := range list {
+		c.index = i
+		c.node = node
+		c.typ = &list[i]
+		applyCursor(v, c)
+		if ast.Node(node) != c.node {
+			list[i] = c.node.(N)
+		}
+	}
+}
+
 // applyCursor traverses an AST in depth-first order: It starts by calling
 // v.Visit(node); node must not be nil. If the visitor w returned by
 // v.Visit(node) is not nil, apply is invoked recursively with visitor
@@ -309,10 +309,7 @@ func applyCursor(v applyVisitor, c Cursor) {
 
 	// TODO: record the comment groups and interleave with the values like for
 	// parsing and printing?
-	comments := node.Comments()
-	for _, cm := range comments {
-		apply(v, c, &cm)
-	}
+	applyList(v, c, ast.Comments(node))
 
 	// apply children
 	// (the order of the cases matches the order
@@ -323,9 +320,7 @@ func applyCursor(v applyVisitor, c Cursor) {
 		// nothing to do
 
 	case *ast.CommentGroup:
-		for _, cg := range n.List {
-			apply(v, c, &cg)
-		}
+		applyList(v, c, n.List)
 
 	case *ast.Attribute:
 		// nothing to do
@@ -335,9 +330,7 @@ func applyCursor(v applyVisitor, c Cursor) {
 		if n.Value != nil {
 			apply(v, c, &n.Value)
 		}
-		for _, a := range n.Attrs {
-			apply(v, c, &a)
-		}
+		applyList(v, c, n.Attrs)
 
 	case *ast.StructLit:
 		n.Elts = applyDeclList(v, c, n.Elts)
@@ -347,10 +340,10 @@ func applyCursor(v applyVisitor, c Cursor) {
 		// nothing to do
 
 	case *ast.Interpolation:
-		applyExprList(v, c, n.Elts)
+		applyList(v, c, n.Elts)
 
 	case *ast.ListLit:
-		applyExprList(v, c, n.Elts)
+		applyList(v, c, n.Elts)
 
 	case *ast.Ellipsis:
 		if n.Type != nil {
@@ -379,7 +372,7 @@ func applyCursor(v applyVisitor, c Cursor) {
 
 	case *ast.CallExpr:
 		apply(v, c, &n.Fun)
-		applyExprList(v, c, n.Args)
+		applyList(v, c, n.Args)
 
 	case *ast.UnaryExpr:
 		apply(v, c, &n.X)
@@ -399,9 +392,7 @@ func applyCursor(v applyVisitor, c Cursor) {
 		// nothing to do
 
 	case *ast.ImportDecl:
-		for _, s := range n.Specs {
-			apply(v, c, &s)
-		}
+		applyList(v, c, n.Specs)
 
 	case *ast.EmbedDecl:
 		apply(v, c, &n.Expr)
@@ -415,10 +406,7 @@ func applyCursor(v applyVisitor, c Cursor) {
 		apply(v, c, &n.Expr)
 
 	case *ast.Comprehension:
-		clauses := n.Clauses
-		for i := range n.Clauses {
-			apply(v, c, &clauses[i])
-		}
+		applyList(v, c, n.Clauses)
 		apply(v, c, &n.Value)
 
 	// Files and packages

cue/ast/walk.go

@@ -41,17 +41,9 @@ type Visitor interface {
 	After(node Node)
 }
 
-// Helper functions for common node lists. They may be empty.
-
-func walkExprList(v Visitor, list []Expr) {
-	for _, x := range list {
-		walk(v, x)
-	}
-}
-
-func walkDeclList(v Visitor, list []Decl) {
-	for _, x := range list {
-		walk(v, x)
+func walkList[N Node](v Visitor, list []N) {
+	for _, node := range list {
+		walk(v, node)
 	}
 }
 
@@ -67,9 +59,7 @@ func walk(v Visitor, node Node) {
 
 	// TODO: record the comment groups and interleave with the values like for
 	// parsing and printing?
-	for _, c := range Comments(node) {
-		walk(v, c)
-	}
+	walkList(v, Comments(node))
 
 	// walk children
 	// (the order of the cases matches the order
@@ -80,9 +70,7 @@ func walk(v Visitor, node Node) {
 		// nothing to do
 
 	case *CommentGroup:
-		for _, c := range n.List {
-			walk(v, c)
-		}
+		walkList(v, n.List)
 
 	case *Attribute:
 		// nothing to do
@@ -92,28 +80,24 @@ func walk(v Visitor, node Node) {
 		if n.Value != nil {
 			walk(v, n.Value)
 		}
-		for _, a := range n.Attrs {
-			walk(v, a)
-		}
+		walkList(v, n.Attrs)
 
 	case *Func:
-		walkExprList(v, n.Args)
+		walkList(v, n.Args)
 		walk(v, n.Ret)
 
 	case *StructLit:
-		walkDeclList(v, n.Elts)
+		walkList(v, n.Elts)
 
 	// Expressions
 	case *BottomLit, *BadExpr, *Ident, *BasicLit:
 		// nothing to do
 
 	case *Interpolation:
-		for _, e := range n.Elts {
-			walk(v, e)
-		}
+		walkList(v, n.Elts)
 
 	case *ListLit:
-		walkExprList(v, n.Elts)
+		walkList(v, n.Elts)
 
 	case *Ellipsis:
 		if n.Type != nil {
@@ -142,7 +126,7 @@ func walk(v Visitor, node Node) {
 
 	case *CallExpr:
 		walk(v, n.Fun)
-		walkExprList(v, n.Args)
+		walkList(v, n.Args)
 
 	case *UnaryExpr:
 		walk(v, n.X)
@@ -162,9 +146,7 @@ func walk(v Visitor, node Node) {
 		// nothing to do
 
 	case *ImportDecl:
-		for _, s := range n.Specs {
-			walk(v, s)
-		}
+		walkList(v, n.Specs)
 
 	case *EmbedDecl:
 		walk(v, n.Expr)
@@ -178,14 +160,12 @@ func walk(v Visitor, node Node) {
 		walk(v, n.Expr)
 
 	case *Comprehension:
-		for _, c := range n.Clauses {
-			walk(v, c)
-		}
+		walkList(v, n.Clauses)
 		walk(v, n.Value)
 
 	// Files and packages
 	case *File:
-		walkDeclList(v, n.Decls)
+		walkList(v, n.Decls)
 
 	case *Package:
 		walk(v, n.Name)