Support uintptr and unsafe.Pointer (#34)

* Support uintptr and unsafe.Pointer

* README: link to golangci-lint usage

* More tests

README.md

@@ -47,28 +47,35 @@ if err != nil {
 ### What if I think it's bullshit?
 
 I understand that each case needs to be analyzed separately, 
-but I hope that the linter will make you think again -
-is it necessary to use an ambiguous API or is it better to do it using a sentinel error?
+but I hope that the linter will make you think again –
+is it necessary to use an **ambiguous API** or is it better to do it using a sentinel error?
 <br>
 
 In any case, you can just not enable the linter.
 
 ## Configuration
 
+### CLI
+
 ```shell
-# command line (see help for full list of types)
+# See help for full list of types.
 $ nilnil --checked-types ptr,func ./...
 ```
 
+### golangci-lint
+
+https://golangci-lint.run/usage/linters/#nilnil
+
 ```yaml
-# https://golangci-lint.run/usage/configuration/
 nilnil:
   checked-types:
     - ptr
     - func
     - iface
     - map
     - chan
+    - uintptr
+    - unsafeptr
 ```
 
 ## Examples
@@ -219,20 +226,12 @@ func (r *RateLimiter) Allow() bool {
 
 ## Assumptions
 
-<details>
-  <summary>Click to expand</summary>
-
-<br>
-
-- Linter only checks functions with two return arguments, the last of which has `error` type.
+- Linter only checks functions with two return arguments, the last of which implements `error`.
 - Next types are checked:
-  * pointers, functions & interfaces (`panic: invalid memory address or nil pointer dereference`);
+  * pointers (including `uinptr` and `unsafe.Pointer`), functions and interfaces (`panic: invalid memory address or nil pointer dereference`);
   * maps (`panic: assignment to entry in nil map`);
   * channels (`fatal error: all goroutines are asleep - deadlock!`)
-- `uinptr` & `unsafe.Pointer` are not checked as a special case.
-- Supported only explicit `return nil, nil`.
-
-</details>
+- Only explicit `return nil, nil` are supported.
 
 ## Check Go 1.22.2 source code
 

pkg/analyzer/analyzer.go

@@ -2,7 +2,9 @@ package analyzer
 
 import (
 	"go/ast"
+	"go/token"
 	"go/types"
+	"strconv"
 
 	"golang.org/x/tools/go/analysis"
 	"golang.org/x/tools/go/analysis/passes/inspect"
@@ -74,13 +76,32 @@ func (n *nilNil) run(pass *analysis.Pass) (interface{}, error) {
 				return false
 			}
 
-			fRes1, fRes2 := ft.Results.List[0], ft.Results.List[1]
-			if !(n.isDangerNilField(pass, fRes1) && n.isErrorField(pass, fRes2)) {
+			fRes1Type := pass.TypesInfo.TypeOf(ft.Results.List[0].Type)
+			if fRes1Type == nil {
 				return false
 			}
 
-			rRes1, rRes2 := v.Results[0], v.Results[1]
-			if isNil(pass, rRes1) && isNil(pass, rRes2) {
+			fRes2Type := pass.TypesInfo.TypeOf(ft.Results.List[1].Type)
+			if fRes2Type == nil {
+				return false
+			}
+
+			ok, zv := n.isDangerNilType(fRes1Type)
+			if !(ok && isErrorType(fRes2Type)) {
+				return false
+			}
+
+			retVal, retErr := v.Results[0], v.Results[1]
+
+			var needWarn bool
+			switch zv {
+			case zeroValueNil:
+				needWarn = isNil(pass, retVal) && isNil(pass, retErr)
+			case zeroValueZero:
+				needWarn = isZero(retVal) && isNil(pass, retErr)
+			}
+
+			if needWarn {
 				pass.Reportf(v.Pos(), reportMsg)
 			}
 		}
@@ -91,41 +112,47 @@ func (n *nilNil) run(pass *analysis.Pass) (interface{}, error) {
 	return nil, nil //nolint:nilnil
 }
 
-func (n *nilNil) isDangerNilField(pass *analysis.Pass, f *ast.Field) bool {
-	return n.isDangerNilType(pass.TypesInfo.TypeOf(f.Type))
-}
+type zeroValue int
 
-func (n *nilNil) isDangerNilType(t types.Type) bool {
+const (
+	zeroValueNil = iota + 1
+	zeroValueZero
+)
+
+func (n *nilNil) isDangerNilType(t types.Type) (bool, zeroValue) {
 	switch v := t.(type) {
 	case *types.Pointer:
-		return n.checkedTypes.Contains(ptrType)
+		return n.checkedTypes.Contains(ptrType), zeroValueNil
 
 	case *types.Signature:
-		return n.checkedTypes.Contains(funcType)
+		return n.checkedTypes.Contains(funcType), zeroValueNil
 
 	case *types.Interface:
-		return n.checkedTypes.Contains(ifaceType)
+		return n.checkedTypes.Contains(ifaceType), zeroValueNil
 
 	case *types.Map:
-		return n.checkedTypes.Contains(mapType)
+		return n.checkedTypes.Contains(mapType), zeroValueNil
 
 	case *types.Chan:
-		return n.checkedTypes.Contains(chanType)
+		return n.checkedTypes.Contains(chanType), zeroValueNil
+
+	case *types.Basic:
+		if v.Kind() == types.Uintptr {
+			return n.checkedTypes.Contains(uintptrType), zeroValueZero
+		}
+		if v.Kind() == types.UnsafePointer {
+			return n.checkedTypes.Contains(unsafeptrType), zeroValueNil
+		}
 
 	case *types.Named:
 		return n.isDangerNilType(v.Underlying())
 	}
-	return false
+	return false, 0
 }
 
 var errorIface = types.Universe.Lookup("error").Type().Underlying().(*types.Interface)
 
-func (n *nilNil) isErrorField(pass *analysis.Pass, f *ast.Field) bool {
-	t := pass.TypesInfo.TypeOf(f.Type)
-	if t == nil {
-		return false
-	}
-
+func isErrorType(t types.Type) bool {
 	_, ok := t.Underlying().(*types.Interface)
 	return ok && types.Implements(t, errorIface)
 }
@@ -139,3 +166,19 @@ func isNil(pass *analysis.Pass, e ast.Expr) bool {
 	_, ok = pass.TypesInfo.ObjectOf(i).(*types.Nil)
 	return ok
 }
+
+func isZero(e ast.Expr) bool {
+	bl, ok := e.(*ast.BasicLit)
+	if !ok {
+		return false
+	}
+	if bl.Kind != token.INT {
+		return false
+	}
+
+	v, err := strconv.ParseInt(bl.Value, 0, 64)
+	if err != nil {
+		return false
+	}
+	return v == 0
+}

pkg/analyzer/analyzer_test.go

@@ -9,9 +9,22 @@ import (
 )
 
 func TestNilNil(t *testing.T) {
+	t.Parallel()
+
 	pkgs := []string{
 		"examples",
 		"strange",
+		"unsafe",
 	}
 	analysistest.Run(t, analysistest.TestData(), analyzer.New(), pkgs...)
 }
+
+func TestNilNil_Flags(t *testing.T) {
+	t.Parallel()
+
+	anlzr := analyzer.New()
+	if err := anlzr.Flags.Set("checked-types", "ptr"); err != nil {
+		t.Fatal(err)
+	}
+	analysistest.Run(t, analysistest.TestData(), anlzr, "pointers-only")
+}

pkg/analyzer/config.go

@@ -8,11 +8,13 @@ import (
 
 func newDefaultCheckedTypes() checkedTypes {
 	return checkedTypes{
-		ptrType:   struct{}{},
-		funcType:  struct{}{},
-		ifaceType: struct{}{},
-		mapType:   struct{}{},
-		chanType:  struct{}{},
+		ptrType:       {},
+		funcType:      {},
+		ifaceType:     {},
+		mapType:       {},
+		chanType:      {},
+		uintptrType:   {},
+		unsafeptrType: {},
 	}
 }
 
@@ -25,15 +27,15 @@ func (t typeName) S() string {
 }
 
 const (
-	ptrType   typeName = "ptr"
-	funcType  typeName = "func"
-	ifaceType typeName = "iface"
-	mapType   typeName = "map"
-	chanType  typeName = "chan"
+	ptrType       typeName = "ptr"
+	funcType      typeName = "func"
+	ifaceType     typeName = "iface"
+	mapType       typeName = "map"
+	chanType      typeName = "chan"
+	uintptrType   typeName = "uintptr"
+	unsafeptrType typeName = "unsafeptr"
 )
 
-var knownTypes = []typeName{ptrType, funcType, ifaceType, mapType, chanType}
-
 type checkedTypes map[typeName]struct{}
 
 func (c checkedTypes) Contains(t typeName) bool {
@@ -60,7 +62,7 @@ func (c checkedTypes) Set(s string) error {
 	c.disableAll()
 	for _, t := range types {
 		switch tt := typeName(t); tt {
-		case ptrType, funcType, ifaceType, mapType, chanType:
+		case ptrType, funcType, ifaceType, mapType, chanType, uintptrType, unsafeptrType:
 			c[tt] = struct{}{}
 		default:
 			return fmt.Errorf("unknown checked type name %q (see help)", t)

pkg/analyzer/config_test.go

@@ -4,33 +4,18 @@ import "testing"
 
 func TestCheckedTypes(t *testing.T) {
 	c := newDefaultCheckedTypes()
-
-	for _, tt := range knownTypes {
-		assertTrue(t, c.Contains(tt))
-	}
-	assertStringEqual(t, c.String(), "chan,func,iface,map,ptr")
+	assertStringEqual(t, c.String(), "chan,func,iface,map,ptr,uintptr,unsafeptr")
 
 	err := c.Set("chan,iface,ptr")
 	assertNoError(t, err)
 	assertTrue(t, c.Contains(chanType))
 	assertTrue(t, c.Contains(ifaceType))
 	assertTrue(t, c.Contains(ptrType))
+	assertFalse(t, c.Contains(funcType))
+	assertFalse(t, c.Contains(mapType))
+	assertFalse(t, c.Contains(uintptrType))
+	assertFalse(t, c.Contains(unsafeptrType))
 	assertStringEqual(t, "chan,iface,ptr", c.String())
-
-	for _, tt := range knownTypes {
-		err := c.Set(tt.S())
-		assertNoError(t, err)
-
-		for _, tt2 := range knownTypes {
-			if tt2 == tt {
-				assertTrue(t, c.Contains(tt2))
-			} else {
-				assertFalse(t, c.Contains(tt2))
-			}
-		}
-
-		assertStringEqual(t, tt.S(), c.String())
-	}
 }
 
 func TestCheckedTypes_SetError(t *testing.T) {
@@ -46,45 +31,40 @@ func TestCheckedTypes_SetWithoutArg(t *testing.T) {
 
 	err := c.Set("")
 	assertNoError(t, err)
-
-	for _, tt := range knownTypes {
-		assertTrue(t, c.Contains(tt))
-	}
-	assertStringEqual(t, c.String(), "chan,func,iface,map,ptr")
+	assertStringEqual(t, c.String(), "chan,func,iface,map,ptr,uintptr,unsafeptr")
 }
 
 func assertError(t *testing.T, err error) {
 	t.Helper()
 	if err == nil {
-		t.FailNow()
+		t.Fatal("must be not nil")
 	}
 }
 
 func assertNoError(t *testing.T, err error) {
 	t.Helper()
 	if err != nil {
-		t.FailNow()
+		t.Fatalf("must be nil, got %q", err)
 	}
 }
 
 func assertStringEqual(t *testing.T, a, b string) {
 	t.Helper()
 	if a != b {
-		t.Logf("%q != %q", a, b)
-		t.FailNow()
+		t.Fatalf("%q != %q", a, b)
 	}
 }
 
 func assertTrue(t *testing.T, v bool) {
 	t.Helper()
 	if !v {
-		t.FailNow()
+		t.Fatal("must be true")
 	}
 }
 
 func assertFalse(t *testing.T, v bool) {
 	t.Helper()
 	if v {
-		t.FailNow()
+		t.Fatal("must be false")
 	}
 }