ruleguard: implement Var.Line filter (#234)

Fixes #146

analyzer/testdata/src/filtertest/f1.go

@@ -230,6 +230,21 @@ func fileFilters1() {
 	importsTest(os.PathListSeparator, "path/filepath")
 }
 
+func detectLine() {
+	lineTest(1, 2, "same line") // want `YES`
+	lineTest(1,
+		2, "same line")
+
+	lineTest( // want `YES`
+		1,
+		2,
+		"different line",
+	)
+	lineTest(1, 2,
+		"different line")
+	lineTest(1, 2, "different line")
+}
+
 func detectNode() {
 	var i int
 	var s string

analyzer/testdata/src/filtertest/linetest4.go

@@ -0,0 +1,6 @@
+package filtertest
+
+func _() {
+	lineTest("", "line 4") // want `YES`
+	lineTest("", "line 4")
+}

analyzer/testdata/src/filtertest/rules.go

@@ -84,6 +84,10 @@ func testRules(m dsl.Matcher) {
 		Where(!m["x"].Pure).
 		Report("!pure")
 
+	m.Match(`lineTest($x, "line 4")`).Where(m["x"].Line == 4).Report(`YES`)
+	m.Match(`lineTest($x, $y, "same line")`).Where(m["x"].Line == m["y"].Line).Report(`YES`)
+	m.Match(`lineTest($x, $y, "different line")`).Where(m["x"].Line != m["y"].Line).Report(`YES`)
+
 	m.Match(`textTest($x, "text=foo")`).Where(m["x"].Text == `foo`).Report(`YES`)
 	m.Match(`textTest($x, "text='foo'")`).Where(m["x"].Text == `"foo"`).Report(`YES`)
 	m.Match(`textTest($x, "text!='foo'")`).Where(m["x"].Text != `"foo"`).Report(`YES`)

analyzer/testdata/src/filtertest/utils.go

@@ -7,6 +7,7 @@ func parensFilterTest(args ...interface{}) {}
 func importsTest(args ...interface{})      {}
 func fileTest(args ...interface{})         {}
 func nodeTest(args ...interface{})         {}
+func lineTest(args ...interface{})         {}
 
 func random() int {
 	return 42

go.mod

@@ -5,7 +5,7 @@ go 1.15
 require (
 	github.com/go-toolsmith/astequal v1.0.0
 	github.com/google/go-cmp v0.5.2
-	github.com/quasilyte/go-ruleguard/dsl v0.3.2
+	github.com/quasilyte/go-ruleguard/dsl v0.3.3
 	github.com/quasilyte/go-ruleguard/rules v0.0.0-20210428214800-545e0d2e0bf7
 	golang.org/x/tools v0.0.0-20201230224404-63754364767c
 )

go.sum

@@ -15,6 +15,8 @@ github.com/quasilyte/go-ruleguard/dsl v0.3.1 h1:CHGOKP2LDz35P49TjW4Bx4BCfFI6ZZU/
 github.com/quasilyte/go-ruleguard/dsl v0.3.1/go.mod h1:KeCP03KrjuSO0H1kTuZQCWlQPulDV6YMIXmpQss17rU=
 github.com/quasilyte/go-ruleguard/dsl v0.3.2 h1:ULi3SLXvDUgb0u2IM5xU6er9KeWBSaUh1NlDjCgLHU8=
 github.com/quasilyte/go-ruleguard/dsl v0.3.2/go.mod h1:KeCP03KrjuSO0H1kTuZQCWlQPulDV6YMIXmpQss17rU=
+github.com/quasilyte/go-ruleguard/dsl v0.3.3 h1:mjurEAavnutTkwBMrSgXHlDcW1VG8XA8ZpJCWvIOe9E=
+github.com/quasilyte/go-ruleguard/dsl v0.3.3/go.mod h1:KeCP03KrjuSO0H1kTuZQCWlQPulDV6YMIXmpQss17rU=
 github.com/quasilyte/go-ruleguard/rules v0.0.0-20201231183845-9e62ed36efe1 h1:PX/E0GYUnSV8vwVfpOUEIBKnPG3KmYunmNOBlL+zDko=
 github.com/quasilyte/go-ruleguard/rules v0.0.0-20201231183845-9e62ed36efe1/go.mod h1:7JTjp89EGyU1d6XfBiXihJNG37wB2VRkd125Q1u7Plc=
 github.com/quasilyte/go-ruleguard/rules v0.0.0-20210203162857-b223e0831f88 h1:PeTrJiH/dSeruL/Z9Db39NRMwI/yoA3oHCdCkg+Wh8A=

ruleguard/filters.go

@@ -169,6 +169,30 @@ func makeTypeAssignableToFilter(src, varname string, dstType types.Type) filterF
 	}
 }
 
+func makeLineFilter(src, varname string, op token.Token, rhsVarname string) filterFunc {
+	return func(params *filterParams) matchFilterResult {
+		line1 := params.ctx.Fset.Position(params.subNode(varname).Pos()).Line
+		line2 := params.ctx.Fset.Position(params.subNode(rhsVarname).Pos()).Line
+		lhsValue := constant.MakeInt64(int64(line1))
+		rhsValue := constant.MakeInt64(int64(line2))
+		if constant.Compare(lhsValue, op, rhsValue) {
+			return filterSuccess
+		}
+		return filterFailure(src)
+	}
+}
+
+func makeLineConstFilter(src, varname string, op token.Token, rhsValue constant.Value) filterFunc {
+	return func(params *filterParams) matchFilterResult {
+		n := params.subNode(varname)
+		lhsValue := constant.MakeInt64(int64(params.ctx.Fset.Position(n.Pos()).Line))
+		if constant.Compare(lhsValue, op, rhsValue) {
+			return filterSuccess
+		}
+		return filterFailure(src)
+	}
+}
+
 func makeTypeSizeConstFilter(src, varname string, op token.Token, rhsValue constant.Value) filterFunc {
 	return func(params *filterParams) matchFilterResult {
 		typ := params.typeofNode(params.subExpr(varname))

ruleguard/parser.go

@@ -664,6 +664,14 @@ func (p *rulesParser) parseFilterExpr(e ast.Expr) matchFilter {
 			operand := p.toFilterOperand(e.X)
 			rhs := p.toFilterOperand(e.Y)
 			rhsValue := p.types.Types[e.Y].Value
+			if operand.path == "Line" && rhsValue != nil {
+				result.fn = makeLineConstFilter(result.src, operand.varName, e.Op, rhsValue)
+				return result
+			}
+			if operand.path == "Line" && rhs.path == "Line" && rhs.varName != "" {
+				result.fn = makeLineFilter(result.src, operand.varName, e.Op, rhs.varName)
+				return result
+			}
 			if operand.path == "Type.Size" && rhsValue != nil {
 				result.fn = makeTypeSizeConstFilter(result.src, operand.varName, e.Op, rhsValue)
 				return result