fix: false-positive useless-assert on Positive function (#236)

* fix: false-positive useless-assert on Positive function when integer type is unsigned

* useless-assert: test and doc

---------

Co-authored-by: Anton Telyshev <[email protected]>

Author: semihbkgr

README.md

@@ -1123,14 +1123,12 @@ assert.Zero(t, false) // Any bool literal.
 assert.Negative(len(x))
 assert.Less(len(x), 0)
 assert.Greater(0, len(x))
-assert.Positive(len(x))
 assert.GreaterOrEqual(len(x), 0)
 assert.LessOrEqual(0, len(x))
 
 assert.Negative(uintVal)
 assert.Less(uintVal, 0)
 assert.Greater(0, uintVal)
-assert.Positive(uintVal)
 assert.GreaterOrEqual(uintVal, 0)
 assert.LessOrEqual(0, uintVal)
 ```

analyzer/testdata/src/checkers-default/useless-assert/useless_assert_test.go

@@ -18,8 +18,7 @@ func (s *BrokenSuite) SetupTest() {
 	var _ suite.TearDownSubTest
 }
 
-func (s *BrokenSuite) SetT() { // *BrokenSuite does not implement suite.TestingSuite (wrong type for method SetT)
-}
+//func (s *BrokenSuite) SetT() {} // *BrokenSuite does not implement suite.TestingSuite (wrong type for method SetT)
 
 func (s *BrokenSuite) TestTypo(_ *testing.T) { // value.go:424: test panicked: reflect: Call with too few input arguments
 	s.True(true)

analyzer/testdata/src/debug/suite_method_signature_test.go

@@ -23,3 +23,7 @@ func TestUselessAsserts(t *testing.T) {
 	assert.Zero(t, "")
 	assert.Zero(t, nil)
 }
+
+func TestPositiveZero(t *testing.T) {
+	assert.Positive(t, uint64(0))
+}

analyzer/testdata/src/debug/useless_assert_test.go

@@ -54,14 +54,12 @@ import (
 //	assert.Negative(len(x))
 //	assert.Less(len(x), 0)
 //	assert.Greater(0, len(x))
-//	assert.Positive(len(x))
 //	assert.GreaterOrEqual(len(x), 0)
 //	assert.LessOrEqual(0, len(x))
 //
 //	assert.Negative(uintVal)
 //	assert.Less(uintVal, 0)
 //	assert.Greater(0, uintVal)
-//	assert.Positive(uintVal)
 //	assert.GreaterOrEqual(uintVal, 0)
 //	assert.LessOrEqual(0, uintVal)
 type UselessAssert struct{}
@@ -94,7 +92,13 @@ func (checker UselessAssert) Check(pass *analysis.Pass, call *CallMeta) *analysi
 	case "LessOrEqual", "Greater":
 		isMeaningless = (len(call.Args) >= 2) && isAnyZero(call.Args[0]) && canNotBeNegative(pass, call.Args[1])
 
-	case "Negative", "Positive":
+	case "Positive":
+		if len(call.Args) < 1 {
+			return nil
+		}
+		_, isMeaningless = isIntBasicLit(call.Args[0])
+
+	case "Negative":
 		if len(call.Args) < 1 {
 			return nil
 		}

internal/checkers/useless_assert.go

@@ -134,14 +134,12 @@ func (g UselessAssertTestsGenerator) TemplateData() any {
 			{Fn: "Negative", Argsf: "len(x)", ReportMsgf: defaultReport},
 			{Fn: "Less", Argsf: "len(x), 0", ReportMsgf: defaultReport},
 			{Fn: "Greater", Argsf: "0, len(x)", ReportMsgf: defaultReport},
-			{Fn: "Positive", Argsf: "len(x)", ReportMsgf: defaultReport},
 			{Fn: "GreaterOrEqual", Argsf: "len(x), 0", ReportMsgf: defaultReport},
 			{Fn: "LessOrEqual", Argsf: "0, len(x)", ReportMsgf: defaultReport},
 
 			{Fn: "Negative", Argsf: "uint(42)", ReportMsgf: defaultReport},
 			{Fn: "Less", Argsf: "uint(42), 0", ReportMsgf: defaultReport},
 			{Fn: "Greater", Argsf: "0, uint(42)", ReportMsgf: defaultReport},
-			{Fn: "Positive", Argsf: "uint(42)", ReportMsgf: defaultReport},
 			{Fn: "GreaterOrEqual", Argsf: "uint(42), 0", ReportMsgf: defaultReport},
 			{Fn: "LessOrEqual", Argsf: "0, uint(42)", ReportMsgf: defaultReport},
 		},
@@ -173,6 +171,12 @@ func (g UselessAssertTestsGenerator) TemplateData() any {
 			{Fn: "Zero", Argsf: "str"},
 			{Fn: "Zero", Argsf: "new(testCase)"},
 			{Fn: "Zero", Argsf: "b"},
+
+			// NOTE(a.telyshev): An unsigned value can be 0.
+			{Fn: "Positive", Argsf: "len(x)"},
+			{Fn: "Positive", Argsf: "uint(42)"},
+			{Fn: "Greater", Argsf: "len(x), 0"},
+			{Fn: "Greater", Argsf: "uint(42), 0"},
 		},
 	}
 }