Move regression tests to public Unmarshal API with full error string assertions

Remove the unstable package test and consolidate all test cases into
TestDecodeError_PositionAfterComment, which exercises toml.Unmarshal
and validates the complete human-readable error output including
context lines and tilde markers.

https://claude.ai/code/session_01EXYfFXc3DDGpQ27sWdXTKq

.github/workflows/cifuzz.yml

@@ -19,7 +19,7 @@ jobs:
         dry-run: false
         language: go
     - name: Upload Crash
-      uses: actions/upload-artifact@v6
+      uses: actions/upload-artifact@v7
       if: failure() && steps.build.outcome == 'success'
       with:
         name: artifacts

.github/workflows/coverage.yml

@@ -15,6 +15,6 @@ jobs:
       - name: Setup go
         uses: actions/setup-go@v6
         with:
-          go-version: "1.25"
+          go-version: "1.26"
       - name: Run tests with coverage
         run: ./ci.sh coverage -d "${GITHUB_BASE_REF-HEAD}"

.github/workflows/go-versions-test.yml

@@ -20,7 +20,7 @@ jobs:
           fetch-depth: 0
 
       - name: Set up Docker Buildx
-        uses: docker/setup-buildx-action@v3
+        uses: docker/setup-buildx-action@v4
 
       - name: Run Go versions compatibility test
         run: |
@@ -28,7 +28,7 @@ jobs:
           ./test-go-versions.sh --output ./test-results $VERSIONS
 
       - name: Upload test results
-        uses: actions/upload-artifact@v6
+        uses: actions/upload-artifact@v7
         with:
           name: go-versions-test-results
           path: |

.github/workflows/lint.yml

@@ -15,7 +15,7 @@ jobs:
       - name: Setup go
         uses: actions/setup-go@v6
         with:
-          go-version: "1.24"
+          go-version: "1.26"
       - name: Run golangci-lint
         uses: golangci/golangci-lint-action@v9
         with:

.github/workflows/release.yml

@@ -22,15 +22,15 @@ jobs:
       - name: Set up Go
         uses: actions/setup-go@v6
         with:
-          go-version: "1.25"
+          go-version: "1.26"
       - name: Login to GitHub Container Registry
-        uses: docker/login-action@v3
+        uses: docker/login-action@v4
         with:
           registry: ghcr.io
           username: ${{ github.actor }}
           password: ${{ secrets.GITHUB_TOKEN }}
       - name: Run GoReleaser
-        uses: goreleaser/goreleaser-action@v6
+        uses: goreleaser/goreleaser-action@v7
         with:
           distribution: goreleaser
           version: '~> v2'

.github/workflows/workflow.yml

@@ -10,9 +10,10 @@ on:
 jobs:
   build:
     strategy:
+      fail-fast: false
       matrix:
         os: [ 'ubuntu-latest', 'windows-latest', 'macos-latest', 'macos-14' ]
-        go: [ '1.24', '1.25' ]
+        go: [ '1.25', '1.26' ]
     runs-on: ${{ matrix.os }}
     name: ${{ matrix.go }}/${{ matrix.os }}
     steps:

.goreleaser.yaml

@@ -22,7 +22,6 @@ builds:
       - linux_riscv64
       - windows_amd64
       - windows_arm64
-      - windows_arm
       - darwin_amd64
       - darwin_arm64
   - id: tomljson
@@ -42,7 +41,6 @@ builds:
       - linux_riscv64
       - windows_amd64
       - windows_arm64
-      - windows_arm
       - darwin_amd64
       - darwin_arm64
   - id: jsontoml
@@ -62,7 +60,6 @@ builds:
       - linux_arm
       - windows_amd64
       - windows_arm64
-      - windows_arm
       - darwin_amd64
       - darwin_arm64
 universal_binaries:

README.md

@@ -239,12 +239,12 @@ Execution time speedup compared to other Go TOML libraries:
         <tr><th>Benchmark</th><th>go-toml v1</th><th>BurntSushi/toml</th></tr>
     </thead>
     <tbody>
-		<tr><td>Marshal/HugoFrontMatter-2</td><td>1.9x</td><td>2.2x</td></tr>
-		<tr><td>Marshal/ReferenceFile/map-2</td><td>1.7x</td><td>2.1x</td></tr>
-		<tr><td>Marshal/ReferenceFile/struct-2</td><td>2.2x</td><td>3.0x</td></tr>
-		<tr><td>Unmarshal/HugoFrontMatter-2</td><td>2.9x</td><td>2.7x</td></tr>
-		<tr><td>Unmarshal/ReferenceFile/map-2</td><td>2.6x</td><td>2.7x</td></tr>
-		<tr><td>Unmarshal/ReferenceFile/struct-2</td><td>4.6x</td><td>5.1x</td></tr>
+        <tr><td>Marshal/HugoFrontMatter-2</td><td>2.1x</td><td>2.0x</td></tr>
+        <tr><td>Marshal/ReferenceFile/map-2</td><td>2.0x</td><td>2.0x</td></tr>
+        <tr><td>Marshal/ReferenceFile/struct-2</td><td>2.3x</td><td>2.5x</td></tr>
+        <tr><td>Unmarshal/HugoFrontMatter-2</td><td>3.3x</td><td>2.8x</td></tr>
+        <tr><td>Unmarshal/ReferenceFile/map-2</td><td>2.9x</td><td>3.0x</td></tr>
+        <tr><td>Unmarshal/ReferenceFile/struct-2</td><td>4.8x</td><td>5.0x</td></tr>
      </tbody>
 </table>
 <details><summary>See more</summary>
@@ -257,17 +257,17 @@ provided for completeness.</p>
         <tr><th>Benchmark</th><th>go-toml v1</th><th>BurntSushi/toml</th></tr>
     </thead>
     <tbody>
-		<tr><td>Marshal/SimpleDocument/map-2</td><td>1.8x</td><td>2.7x</td></tr>
-		<tr><td>Marshal/SimpleDocument/struct-2</td><td>2.7x</td><td>3.8x</td></tr>
-		<tr><td>Unmarshal/SimpleDocument/map-2</td><td>3.8x</td><td>3.0x</td></tr>
-		<tr><td>Unmarshal/SimpleDocument/struct-2</td><td>5.6x</td><td>4.1x</td></tr>
-		<tr><td>UnmarshalDataset/example-2</td><td>3.0x</td><td>3.2x</td></tr>
-		<tr><td>UnmarshalDataset/code-2</td><td>2.3x</td><td>2.9x</td></tr>
-		<tr><td>UnmarshalDataset/twitter-2</td><td>2.6x</td><td>2.7x</td></tr>
-		<tr><td>UnmarshalDataset/citm_catalog-2</td><td>2.2x</td><td>2.3x</td></tr>
-		<tr><td>UnmarshalDataset/canada-2</td><td>1.8x</td><td>1.5x</td></tr>
-		<tr><td>UnmarshalDataset/config-2</td><td>4.1x</td><td>2.9x</td></tr>
-		<tr><td>geomean</td><td>2.7x</td><td>2.8x</td></tr>
+        <tr><td>Marshal/SimpleDocument/map-2</td><td>2.0x</td><td>2.9x</td></tr>
+        <tr><td>Marshal/SimpleDocument/struct-2</td><td>2.5x</td><td>3.6x</td></tr>
+        <tr><td>Unmarshal/SimpleDocument/map-2</td><td>4.2x</td><td>3.4x</td></tr>
+        <tr><td>Unmarshal/SimpleDocument/struct-2</td><td>5.9x</td><td>4.4x</td></tr>
+        <tr><td>UnmarshalDataset/example-2</td><td>3.2x</td><td>2.9x</td></tr>
+        <tr><td>UnmarshalDataset/code-2</td><td>2.4x</td><td>2.8x</td></tr>
+        <tr><td>UnmarshalDataset/twitter-2</td><td>2.7x</td><td>2.5x</td></tr>
+        <tr><td>UnmarshalDataset/citm_catalog-2</td><td>2.3x</td><td>2.3x</td></tr>
+        <tr><td>UnmarshalDataset/canada-2</td><td>1.9x</td><td>1.5x</td></tr>
+        <tr><td>UnmarshalDataset/config-2</td><td>5.4x</td><td>3.0x</td></tr>
+        <tr><td>geomean</td><td>2.9x</td><td>2.8x</td></tr>
      </tbody>
 </table>
 <p>This table can be generated with <code>./ci.sh benchmark -a -html</code>.</p>

ci.sh

@@ -147,7 +147,7 @@ bench() {
     pushd "$dir"
 
     if [ "${replace}" != "" ]; then
-        find ./benchmark/ -iname '*.go' -exec sed -i -E "s|github.com/pelletier/go-toml/v2|${replace}|g" {} \;
+        find ./benchmark/ -iname '*.go' -exec sed -i -E "s|github.com/pelletier/go-toml/v2\"|${replace}\"|g" {} \;
         go get "${replace}"
     fi
 
@@ -195,6 +195,11 @@ for line in reversed(lines[2:]):
         "%.1fx" % (float(line[3])/v2),  # v1
         "%.1fx" % (float(line[7])/v2),  # bs
     ])
+
+if not results:
+    print("No benchmark results to display.", file=sys.stderr)
+    sys.exit(1)
+
 # move geomean to the end
 results.append(results[0])
 del results[0]

errors_test.go

@@ -259,6 +259,12 @@ func TestDecodeError_Position(t *testing.T) {
 			expectedRow: 3,
 			minCol:      5,
 		},
+		{
+			name:        "missing equals on last line without trailing newline",
+			doc:         "a = 1\nb = 2\nc",
+			expectedRow: 3,
+			minCol:      1,
+		},
 	}
 
 	for _, e := range examples {
@@ -295,6 +301,73 @@ OtherMissing = 1
 	assert.Equal(t, 2, len(strictErr.Unwrap()))
 }
 
+func TestDecodeError_PositionAfterComment(t *testing.T) {
+	// Regression test for https://github.com/pelletier/go-toml/issues/1047
+	// Error positions must be correct when the error occurs after comments or
+	// other content that was already scanned past.
+	examples := []struct {
+		desc        string
+		doc         string
+		expectedRow int
+		expectedCol int
+		expectedStr string
+	}{
+		{
+			desc:        "invalid key after comment",
+			doc:         "# comment\n= \"value\"",
+			expectedRow: 2,
+			expectedCol: 1,
+			expectedStr: "1| # comment\n2| = \"value\"\n | ~ invalid character at start of key: =",
+		},
+		{
+			desc:        "invalid key after two comments",
+			doc:         "# one\n# two\n= \"value\"",
+			expectedRow: 3,
+			expectedCol: 1,
+			expectedStr: "1| # one\n2| # two\n3| = \"value\"\n | ~ invalid character at start of key: =",
+		},
+		{
+			desc:        "invalid key after key-value pair",
+			doc:         "a = 1\n= 2",
+			expectedRow: 2,
+			expectedCol: 1,
+			expectedStr: "1| a = 1\n2| = 2\n | ~ invalid character at start of key: =",
+		},
+		{
+			desc:        "invalid key after blank line",
+			doc:         "a = 1\n\n= 2",
+			expectedRow: 3,
+			expectedCol: 1,
+			expectedStr: "1| a = 1\n2|\n3| = 2\n | ~ invalid character at start of key: =",
+		},
+	}
+
+	for _, e := range examples {
+		t.Run(e.desc, func(t *testing.T) {
+			var v interface{}
+			err := Unmarshal([]byte(e.doc), &v)
+			if err == nil {
+				t.Fatal("expected an error")
+			}
+
+			var derr *DecodeError
+			if !errors.As(err, &derr) {
+				t.Fatalf("error not a *DecodeError: %T: %v", err, err)
+			}
+
+			row, col := derr.Position()
+			if row != e.expectedRow {
+				t.Errorf("row: got %d, want %d (error: %s)", row, e.expectedRow, derr.String())
+			}
+			if col != e.expectedCol {
+				t.Errorf("col: got %d, want %d (error: %s)", col, e.expectedCol, derr.String())
+			}
+
+			assert.Equal(t, e.expectedStr, derr.String())
+		})
+	}
+}
+
 func ExampleDecodeError() {
 	doc := `name = 123__456`
 

marshaler.go

@@ -704,15 +704,18 @@ func (enc *Encoder) encodeMap(b []byte, ctx encoderCtx, v reflect.Value) ([]byte
 	for iter.Next() {
 		v := iter.Value()
 
-		if isNil(v) {
-			// For nil pointers, convert to zero value of the element type.
-			// This allows round-trip marshaling of maps with nil pointer values.
-			// For nil interfaces and nil maps, skip since we can't derive a type.
-			if v.Kind() == reflect.Ptr {
+		// Handle nil values: convert nil pointers to zero value,
+		// skip nil interfaces and nil maps.
+		switch v.Kind() {
+		case reflect.Ptr:
+			if v.IsNil() {
 				v = reflect.Zero(v.Type().Elem())
-			} else {
+			}
+		case reflect.Interface, reflect.Map:
+			if v.IsNil() {
 				continue
 			}
+		default:
 		}
 
 		k, err := enc.keyToString(iter.Key())
@@ -936,7 +939,7 @@ func (enc *Encoder) encodeTable(b []byte, ctx encoderCtx, t table) ([]byte, erro
 		if shouldOmitEmpty(kv.Options, kv.Value) {
 			continue
 		}
-		if shouldOmitZero(kv.Options, kv.Value) {
+		if kv.Options.omitzero && shouldOmitZero(kv.Options, kv.Value) {
 			continue
 		}
 		hasNonEmptyKV = true
@@ -958,7 +961,7 @@ func (enc *Encoder) encodeTable(b []byte, ctx encoderCtx, t table) ([]byte, erro
 		if shouldOmitEmpty(table.Options, table.Value) {
 			continue
 		}
-		if shouldOmitZero(table.Options, table.Value) {
+		if table.Options.omitzero && shouldOmitZero(table.Options, table.Value) {
 			continue
 		}
 		if first {
@@ -995,7 +998,7 @@ func (enc *Encoder) encodeTableInline(b []byte, ctx encoderCtx, t table) ([]byte
 		if shouldOmitEmpty(kv.Options, kv.Value) {
 			continue
 		}
-		if shouldOmitZero(kv.Options, kv.Value) {
+		if kv.Options.omitzero && shouldOmitZero(kv.Options, kv.Value) {
 			continue
 		}
 

test-go-versions.sh

@@ -9,7 +9,7 @@ YELLOW='\033[1;33m'
 BLUE='\033[0;34m'
 NC='\033[0m' # No Color
 
-# Go versions to test (1.11 through 1.25)
+# Go versions to test (1.11 through 1.26)
 GO_VERSIONS=(
     "1.11"
     "1.12"
@@ -26,6 +26,7 @@ GO_VERSIONS=(
     "1.23"
     "1.24"
     "1.25"
+    "1.26"
 )
 
 # Default values
@@ -64,7 +65,7 @@ EXAMPLES:
     $0                          # Test all Go versions in parallel
     $0 --sequential             # Test all Go versions sequentially
     $0 1.21 1.22 1.23          # Test specific versions
-    $0 --verbose --output ./results 1.24 1.25  # Verbose output to custom directory
+    $0 --verbose --output ./results 1.25 1.26  # Verbose output to custom directory
 
 EXIT CODES:
     0                   Recent Go versions pass (good compatibility)
@@ -136,8 +137,8 @@ fi
 
 # Validate Go versions
 for version in "${GO_VERSIONS[@]}"; do
-    if ! [[ "$version" =~ ^1\.(1[1-9]|2[0-5])$ ]]; then
-        log_error "Invalid Go version: $version. Supported versions: 1.11-1.25"
+    if ! [[ "$version" =~ ^1\.(1[1-9]|2[0-6])$ ]]; then
+        log_error "Invalid Go version: $version. Supported versions: 1.11-1.26"
         exit 1
     fi
 done

unmarshaler_test.go

@@ -4554,266 +4554,10 @@ func (c *customTable873) UnmarshalTOML(data []byte) error {
 		c.Keys = append(c.Keys, key)
 		c.Values[key] = string(valueBytes)
 	}
+
 	return nil
 }
 
-func TestIssue873_TableUnmarshaler(t *testing.T) {
-	type Config struct {
-		Section customTable873 `toml:"section"`
-	}
-
-	doc := `
-[section]
-key1 = "value1"
-key2 = "value2"
-key3 = "value3"
-`
-
-	var cfg Config
-	err := toml.NewDecoder(bytes.NewReader([]byte(doc))).
-		EnableUnmarshalerInterface().
-		Decode(&cfg)
-
-	assert.NoError(t, err)
-	assert.Equal(t, []string{"key1", "key2", "key3"}, cfg.Section.Keys)
-	assert.Equal(t, "value1", cfg.Section.Values["key1"])
-	assert.Equal(t, "value2", cfg.Section.Values["key2"])
-	assert.Equal(t, "value3", cfg.Section.Values["key3"])
-}
-
-func TestIssue873_TableUnmarshaler_EmptyTable(t *testing.T) {
-	type Config struct {
-		Section customTable873 `toml:"section"`
-	}
-
-	doc := `
-[section]
-`
-
-	var cfg Config
-	err := toml.NewDecoder(bytes.NewReader([]byte(doc))).
-		EnableUnmarshalerInterface().
-		Decode(&cfg)
-
-	assert.NoError(t, err)
-	assert.Equal(t, []string{}, cfg.Section.Keys)
-}
-
-func TestIssue873_ArrayTableUnmarshaler(t *testing.T) {
-	type Config struct {
-		Items []customTable873 `toml:"items"`
-	}
-
-	doc := `
-[[items]]
-name = "first"
-id = "1"
-
-[[items]]
-name = "second"
-id = "2"
-`
-
-	var cfg Config
-	err := toml.NewDecoder(bytes.NewReader([]byte(doc))).
-		EnableUnmarshalerInterface().
-		Decode(&cfg)
-
-	assert.NoError(t, err)
-	assert.Equal(t, 2, len(cfg.Items))
-	assert.Equal(t, []string{"name", "id"}, cfg.Items[0].Keys)
-	assert.Equal(t, "first", cfg.Items[0].Values["name"])
-	assert.Equal(t, "1", cfg.Items[0].Values["id"])
-	assert.Equal(t, []string{"name", "id"}, cfg.Items[1].Keys)
-	assert.Equal(t, "second", cfg.Items[1].Values["name"])
-	assert.Equal(t, "2", cfg.Items[1].Values["id"])
-}
-
-func TestIssue873_NestedTableUnmarshaler(t *testing.T) {
-	type Config struct {
-		Outer struct {
-			Inner customTable873 `toml:"inner"`
-		} `toml:"outer"`
-	}
-
-	doc := `
-[outer.inner]
-a = "A"
-b = "B"
-`
-
-	var cfg Config
-	err := toml.NewDecoder(bytes.NewReader([]byte(doc))).
-		EnableUnmarshalerInterface().
-		Decode(&cfg)
-
-	assert.NoError(t, err)
-	assert.Equal(t, []string{"a", "b"}, cfg.Outer.Inner.Keys)
-	assert.Equal(t, "A", cfg.Outer.Inner.Values["a"])
-	assert.Equal(t, "B", cfg.Outer.Inner.Values["b"])
-}
-
-func TestIssue873_TableUnmarshaler_MultipleTables(t *testing.T) {
-	type Config struct {
-		First  customTable873 `toml:"first"`
-		Second customTable873 `toml:"second"`
-	}
-
-	doc := `
-[first]
-key1 = "value1"
-
-[second]
-key2 = "value2"
-`
-
-	var cfg Config
-	err := toml.NewDecoder(bytes.NewReader([]byte(doc))).
-		EnableUnmarshalerInterface().
-		Decode(&cfg)
-
-	assert.NoError(t, err)
-	assert.Equal(t, []string{"key1"}, cfg.First.Keys)
-	assert.Equal(t, "value1", cfg.First.Values["key1"])
-	assert.Equal(t, []string{"key2"}, cfg.Second.Keys)
-	assert.Equal(t, "value2", cfg.Second.Values["key2"])
-}
-
-// Test that regular struct fields still work alongside Unmarshaler tables
-func TestIssue873_MixedWithRegularFields(t *testing.T) {
-	type Config struct {
-		Name    string         `toml:"name"`
-		Section customTable873 `toml:"section"`
-		Count   int            `toml:"count"`
-	}
-
-	doc := `
-name = "test"
-count = 42
-
-[section]
-foo = "bar"
-`
-
-	var cfg Config
-	err := toml.NewDecoder(bytes.NewReader([]byte(doc))).
-		EnableUnmarshalerInterface().
-		Decode(&cfg)
-
-	assert.NoError(t, err)
-	assert.Equal(t, "test", cfg.Name)
-	assert.Equal(t, 42, cfg.Count)
-	assert.Equal(t, []string{"foo"}, cfg.Section.Keys)
-	assert.Equal(t, "bar", cfg.Section.Values["foo"])
-}
-
-// Test that pointer to Unmarshaler type works
-func TestIssue873_PointerToUnmarshaler(t *testing.T) {
-	type Config struct {
-		Section *customTable873 `toml:"section"`
-	}
-
-	doc := `
-[section]
-hello = "world"
-`
-
-	var cfg Config
-	err := toml.NewDecoder(bytes.NewReader([]byte(doc))).
-		EnableUnmarshalerInterface().
-		Decode(&cfg)
-
-	assert.NoError(t, err)
-	assert.True(t, cfg.Section != nil)
-	assert.Equal(t, []string{"hello"}, cfg.Section.Keys)
-	assert.Equal(t, "world", cfg.Section.Values["hello"])
-}
-
-// Test table with sub-tables defined separately
-func TestIssue873_TableWithSubTables(t *testing.T) {
-	type Config struct {
-		Parent customTable873 `toml:"parent"`
-	}
-
-	doc := `
-[parent]
-name = "root"
-
-[parent.child]
-name = "nested"
-`
-
-	var cfg Config
-	err := toml.NewDecoder(bytes.NewReader([]byte(doc))).
-		EnableUnmarshalerInterface().
-		Decode(&cfg)
-
-	// The parent should only get the keys directly under [parent],
-	// not the [parent.child] sub-table
-	assert.NoError(t, err)
-	assert.Equal(t, []string{"name"}, cfg.Parent.Keys)
-	assert.Equal(t, "root", cfg.Parent.Values["name"])
-}
-
-// Test for issue #994 follow-up - tables defined piece-wise
-// This addresses the maintainer's comment: "It doesn't deal with tables defined piece-wise yet"
-func TestIssue994_TablesPieceWise(t *testing.T) {
-	// Test with piece-wise table definition (using [table] syntax)
-	// The customTable873 type captures key-value pairs in order,
-	// which is useful for use cases like maintaining map ordering
-	doc := `
-[section]
-first = "1"
-second = "2"
-third = "3"
-`
-
-	type Config struct {
-		Section customTable873 `toml:"section"`
-	}
-
-	var cfg Config
-	err := toml.NewDecoder(bytes.NewReader([]byte(doc))).
-		EnableUnmarshalerInterface().
-		Decode(&cfg)
-
-	assert.NoError(t, err)
-	// Verify ordering is preserved (keys are collected in document order)
-	assert.Equal(t, []string{"first", "second", "third"}, cfg.Section.Keys)
-	assert.Equal(t, "1", cfg.Section.Values["first"])
-	assert.Equal(t, "2", cfg.Section.Values["second"])
-	assert.Equal(t, "3", cfg.Section.Values["third"])
-}
-
-// Test root-level struct with tables - combines #994 fix with #873 enhancement
-func TestIssue994_RootWithTables(t *testing.T) {
-	type rootDoc struct {
-		Tables []customTable873 `toml:"tables"`
-	}
-
-	doc := `
-[[tables]]
-name = "first"
-value = "one"
-
-[[tables]]
-name = "second"
-value = "two"
-`
-
-	var d rootDoc
-	err := toml.NewDecoder(bytes.NewReader([]byte(doc))).
-		EnableUnmarshalerInterface().
-		Decode(&d)
-
-	assert.NoError(t, err)
-	assert.Equal(t, 2, len(d.Tables))
-	assert.Equal(t, "first", d.Tables[0].Values["name"])
-	assert.Equal(t, "one", d.Tables[0].Values["value"])
-	assert.Equal(t, "second", d.Tables[1].Values["name"])
-	assert.Equal(t, "two", d.Tables[1].Values["value"])
-}
-
 // Test for split tables - when the same parent table is defined in multiple places
 // This is a key requirement for issue #873: if type A implements Unmarshaler,
 // and [a.b] and [a.d] are defined with another table [x] in between,

unstable/ast.go

@@ -28,12 +28,16 @@ func (c *Iterator) Next() bool {
 	if c.nodes == nil {
 		return false
 	}
+	nodes := *c.nodes
 	if !c.started {
 		c.started = true
-	} else if c.idx >= 0 {
-		c.idx = (*c.nodes)[c.idx].next
+	} else {
+		idx := c.idx
+		if idx >= 0 && int(idx) < len(nodes) {
+			c.idx = nodes[idx].next
 		}
-	return c.idx >= 0 && int(c.idx) < len(*c.nodes)
+	}
+	return c.idx >= 0 && int(c.idx) < len(nodes)
 }
 
 // IsLast returns true if the current node of the iterator is the last

unstable/parser.go

@@ -3,6 +3,7 @@ package unstable
 import (
 	"bytes"
 	"fmt"
+	"reflect"
 	"unicode"
 
 	"github.com/pelletier/go-toml/v2/internal/characters"
@@ -83,10 +84,14 @@ func (p *Parser) rangeOfToken(token, rest []byte) Range {
 }
 
 // subsliceOffset returns the byte offset of subslice b within p.data.
-// b must be a suffix (tail) of p.data.
+// b must be a subslice of p.data (sharing the same backing array).
 func (p *Parser) subsliceOffset(b []byte) int {
-	// b is a suffix of p.data, so its offset is len(p.data) - len(b)
-	return len(p.data) - len(b)
+	if len(b) == 0 {
+		return 0
+	}
+	dataPtr := reflect.ValueOf(p.data).Pointer()
+	subPtr := reflect.ValueOf(b).Pointer()
+	return int(subPtr - dataPtr)
 }
 
 // Raw returns the slice corresponding to the bytes in the given range.
@@ -345,7 +350,7 @@ func (p *Parser) parseKeyval(b []byte) (reference, []byte, error) {
 	b = p.parseWhitespace(b)
 
 	if len(b) == 0 {
-		return invalidReference, nil, NewParserError(b, "expected = after a key, but the document ends there")
+		return invalidReference, nil, NewParserError(startB[:len(startB)-len(b)], "expected = after a key, but the document ends there")
 	}
 
 	b, err = expect('=', b)
@@ -363,9 +368,10 @@ func (p *Parser) parseKeyval(b []byte) (reference, []byte, error) {
 	p.builder.Chain(valRef, key)
 	p.builder.AttachChild(ref, valRef)
 
-	// Set Raw to span the entire key-value expression
-	node := p.builder.NodeAt(ref)
-	node.Raw = p.rangeOfToken(startB[:len(startB)-len(b)], b)
+	// Set Raw to span the entire key-value expression.
+	// Access the node directly in the slice to avoid the write barrier
+	// that NodeAt's nodes-pointer setup would trigger.
+	p.builder.tree.nodes[ref].Raw = p.rangeOfToken(startB[:len(startB)-len(b)], b)
 
 	return ref, b, err
 }