fix: panic with range over iter.Seq

Author: ldez

contextcheck.go

@@ -727,6 +727,14 @@ func (r *runner) getFunction(instr ssa.Instruction) (f *ssa.Function) {
 }
 
 func (r *runner) isCtxType(tp types.Type) bool {
+	if p, ok := tp.(*types.Pointer); ok {
+		// opaqueType is not exposed and lead to unreachable error.
+		// Related to https://github.com/golang/tools/blob/63229bc79404d8cf2fe4e88ad569168fe251d993/go/ssa/builder.go#L107
+		if p.Elem().String() == "deferStack" {
+			return false
+		}
+	}
+
 	return types.Identical(tp, r.ctxTyp) || types.Identical(tp, r.ctxPTyp)
 }
 

testdata/src/a/a.go

@@ -3,6 +3,7 @@ package a // want package:"ctxCheck"
 import (
 	"context"
 	"net/http"
+	"slices"
 )
 
 type MyString string
@@ -171,3 +172,13 @@ func f17(ctx context.Context, k string) func() func() {
 		}
 	}
 }
+
+/* ----------------- range over iter.Seq ----------------- */
+
+func fIterSeq() {
+	seq := slices.Values([]any{"a"})
+	for range seq {
+		_, cancel := context.WithCancel(context.Background())
+		defer cancel()
+	}
+}