feat: add foreshadow linter

Author: Crocmagnon

.golangci.next.reference.yml

@@ -2534,6 +2534,7 @@ linters:
     - exportloopref
     - forbidigo
     - forcetypeassert
+    - foreshadow
     - funlen
     - gci
     - ginkgolinter
@@ -2647,6 +2648,7 @@ linters:
     - exportloopref
     - forbidigo
     - forcetypeassert
+    - foreshadow
     - funlen
     - gci
     - ginkgolinter

go.mod

@@ -11,6 +11,7 @@ require (
 	github.com/Antonboom/nilnil v0.1.7
 	github.com/Antonboom/testifylint v1.2.0
 	github.com/BurntSushi/toml v1.3.2
+	github.com/Crocmagnon/foreshadow v0.1.2
 	github.com/Djarvur/go-err113 v0.0.0-20210108212216-aea10b59be24
 	github.com/GaijinEntertainment/go-exhaustruct/v3 v3.2.0
 	github.com/OpenPeeDeeP/depguard/v2 v2.2.0

go.sum

@@ -237,6 +237,7 @@
             "exportloopref",
             "forbidigo",
             "forcetypeassert",
+            "foreshadow",
             "funlen",
             "gci",
             "ginkgolinter",

jsonschema/golangci.next.jsonschema.json

@@ -0,0 +1,17 @@
+package golinters
+
+import (
+	"github.com/Crocmagnon/foreshadow/pkg/analyzer"
+	"golang.org/x/tools/go/analysis"
+
+	"github.com/golangci/golangci-lint/pkg/goanalysis"
+)
+
+func NewForeshadow() *goanalysis.Linter {
+	return goanalysis.NewLinter(
+		"foreshadow",
+		"Enforces context shadowing inside loops",
+		[]*analysis.Analyzer{analyzer.Analyzer},
+		nil,
+	).WithLoadMode(goanalysis.LoadModeTypesInfo)
+}

pkg/golinters/foreshadow.go

@@ -181,6 +181,12 @@ func (b LinterBuilder) Build(cfg *config.Config) ([]*linter.Config, error) {
 			WithPresets(linter.PresetStyle).
 			WithURL("https://github.com/gostaticanalysis/forcetypeassert"),
 
+		linter.NewConfig(golinters.NewForeshadow()).
+			WithSince("1.58.0").
+			WithPresets(linter.PresetPerformance).
+			WithLoadForGoAnalysis().
+			WithURL("https://github.com/Crocmagnon/foreshadow"),
+
 		linter.NewConfig(golinters.NewFunlen(&cfg.LintersSettings.Funlen)).
 			WithSince("v1.18.0").
 			WithPresets(linter.PresetComplexity).

pkg/lint/lintersdb/builder_linter.go

@@ -0,0 +1,33 @@
+//golangcitest:args -Eforeshadow
+package testdata
+
+import "context"
+
+func example() {
+	ctx := context.Background()
+
+	for i := 0; i < 10; i++ {
+		ctx := context.WithValue(ctx, "key", i)
+		ctx = context.WithValue(ctx, "other", "val")
+	}
+
+	for i := 0; i < 10; i++ {
+		ctx = context.WithValue(ctx, "key", i) // want "context not shadowed in loop"
+		ctx = context.WithValue(ctx, "other", "val")
+	}
+
+	for item := range []string{"one", "two", "three"} {
+		ctx = wrapContext(ctx) // want "context not shadowed in loop"
+		ctx := context.WithValue(ctx, "key", item)
+		ctx = wrapContext(ctx)
+	}
+
+	for {
+		ctx = wrapContext(ctx) // want "context not shadowed in loop"
+		break
+	}
+}
+
+func wrapContext(ctx context.Context) context.Context {
+	return context.WithoutCancel(ctx)
+}