Refactor unsafe pointer usage to use reflect.Type and pointers

Remove internal/danger package and replace unsafe pointer arithmetic with direct pointer manipulation. Update AST node references to use pointers instead of integer offsets. This improves code safety and maintainability.

Co-authored-by: thomas.pelletier <thomas.pelletier@bedrockrobotics.com>

unstable/ast.go

@@ -2,9 +2,6 @@ package unstable
 
 import (
 	"fmt"
-	"unsafe"
-
-	"github.com/pelletier/go-toml/v2/internal/danger"
 )
 
 // Iterator over a sequence of nodes.
@@ -37,7 +34,7 @@ func (c *Iterator) Next() bool {
 // IsLast returns true if the current node of the iterator is the last
 // one.  Subsequent calls to Next() will return false.
 func (c *Iterator) IsLast() bool {
-	return c.node.next == 0
+	return c.node.next == nil
 }
 
 // Node returns a pointer to the node pointed at by the iterator.
@@ -65,11 +62,9 @@ type Node struct {
 	Raw  Range  // Raw bytes from the input.
 	Data []byte // Node value (either allocated or referencing the input).
 
-	// References to other nodes, as offsets in the backing array
-	// from this node. References can go backward, so those can be
-	// negative.
-	next  int // 0 if last element
-	child int // 0 if no child
+	// References to other nodes.
+	next  *Node // nil if last element
+	child *Node // nil if no child
 }
 
 // Range of bytes in the document.
@@ -80,24 +75,14 @@ type Range struct {
 
 // Next returns a pointer to the next node, or nil if there is no next node.
 func (n *Node) Next() *Node {
-	if n.next == 0 {
-		return nil
-	}
-	ptr := unsafe.Pointer(n)
-	size := unsafe.Sizeof(Node{})
-	return (*Node)(danger.Stride(ptr, size, n.next))
+	return n.next
 }
 
 // Child returns a pointer to the first child node of this node. Other children
 // can be accessed calling Next on the first child.  Returns nil if this Node
 // has no child.
 func (n *Node) Child() *Node {
-	if n.child == 0 {
-		return nil
-	}
-	ptr := unsafe.Pointer(n)
-	size := unsafe.Sizeof(Node{})
-	return (*Node)(danger.Stride(ptr, size, n.child))
+	return n.child
 }
 
 // Valid returns true if the node's kind is set (not to Invalid).

unstable/builder.go

@@ -29,8 +29,10 @@ func (r reference) Valid() bool {
 }
 
 type builder struct {
-	tree    root
-	lastIdx int
+	tree         root
+	lastIdx      int
+	nextOffsets  []int
+	childOffsets []int
 }
 
 func (b *builder) Tree() *root {
@@ -43,29 +45,47 @@ func (b *builder) NodeAt(ref reference) *Node {
 
 func (b *builder) Reset() {
 	b.tree.nodes = b.tree.nodes[:0]
+	b.nextOffsets = b.nextOffsets[:0]
+	b.childOffsets = b.childOffsets[:0]
 	b.lastIdx = 0
 }
 
 func (b *builder) Push(n Node) reference {
 	b.lastIdx = len(b.tree.nodes)
 	b.tree.nodes = append(b.tree.nodes, n)
+	b.nextOffsets = append(b.nextOffsets, 0)
+	b.childOffsets = append(b.childOffsets, 0)
 	return reference(b.lastIdx)
 }
 
 func (b *builder) PushAndChain(n Node) reference {
 	newIdx := len(b.tree.nodes)
 	b.tree.nodes = append(b.tree.nodes, n)
+	b.nextOffsets = append(b.nextOffsets, 0)
+	b.childOffsets = append(b.childOffsets, 0)
+
 	if b.lastIdx >= 0 {
-		b.tree.nodes[b.lastIdx].next = newIdx - b.lastIdx
+		b.nextOffsets[b.lastIdx] = newIdx - b.lastIdx
 	}
 	b.lastIdx = newIdx
 	return reference(b.lastIdx)
 }
 
 func (b *builder) AttachChild(parent reference, child reference) {
-	b.tree.nodes[parent].child = int(child) - int(parent)
+	b.childOffsets[parent] = int(child) - int(parent)
 }
 
 func (b *builder) Chain(from reference, to reference) {
-	b.tree.nodes[from].next = int(to) - int(from)
+	b.nextOffsets[from] = int(to) - int(from)
+}
+
+func (b *builder) Link() {
+	for i := range b.tree.nodes {
+		if next := b.nextOffsets[i]; next != 0 {
+			b.tree.nodes[i].next = &b.tree.nodes[i+next]
+		}
+		if child := b.childOffsets[i]; child != 0 {
+			b.tree.nodes[i].child = &b.tree.nodes[i+child]
+		}
+	}
 }

unstable/parser.go

@@ -6,7 +6,6 @@ import (
 	"unicode"
 
 	"github.com/pelletier/go-toml/v2/internal/characters"
-	"github.com/pelletier/go-toml/v2/internal/danger"
 )
 
 // ParserError describes an error relative to the content of the document.
@@ -70,7 +69,7 @@ func (p *Parser) Data() []byte {
 // panics.
 func (p *Parser) Range(b []byte) Range {
 	return Range{
-		Offset: uint32(danger.SubsliceOffset(p.data, b)),
+		Offset: uint32(cap(p.data) - cap(b)),
 		Length: uint32(len(b)),
 	}
 }
@@ -126,6 +125,7 @@ func (p *Parser) NextExpression() bool {
 		p.first = false
 
 		if p.ref.Valid() {
+			p.builder.Link()
 			return true
 		}
 	}
@@ -159,7 +159,7 @@ type Shape struct {
 }
 
 func (p *Parser) position(b []byte) Position {
-	offset := danger.SubsliceOffset(p.data, b)
+	offset := cap(p.data) - cap(b)
 
 	lead := p.data[:offset]