pkg/eval: Don't use the new context.Cause API.

Elvish should still be buildable with Go 1.19.

pkg/eval/builtin_fn_time.go

@@ -1,7 +1,6 @@
 package eval
 
 import (
-	"context"
 	"fmt"
 	"math"
 	"math/big"
@@ -54,7 +53,7 @@ func sleep(fm *Frame, duration any) error {
 
 	select {
 	case <-fm.Context().Done():
-		return context.Cause(fm.Context())
+		return ErrInterrupted
 	case <-timeAfter(fm, d):
 		return nil
 	}

pkg/eval/compile_effect.go

@@ -38,8 +38,8 @@ func (op chunkOp) exec(fm *Frame) Exception {
 	// Check for interrupts after the chunk.
 	// We also check for interrupts before each pipeline, so there is no
 	// need to check it before the chunk or after each pipeline.
-	if err := fm.CancelCause(); err != nil {
-		return fm.errorp(op, err)
+	if fm.Canceled() {
+		return fm.errorp(op, ErrInterrupted)
 	}
 	return nil
 }
@@ -68,8 +68,8 @@ type pipelineOp struct {
 const pipelineChanBufferSize = 32
 
 func (op *pipelineOp) exec(fm *Frame) Exception {
-	if err := fm.CancelCause(); err != nil {
-		return fm.errorp(op, err)
+	if fm.Canceled() {
+		return fm.errorp(op, ErrInterrupted)
 	}
 
 	if op.bg {

pkg/eval/frame.go

@@ -180,14 +180,13 @@ func (fm *Frame) Context() context.Context {
 	return fm.ctx
 }
 
-// CancelCause checks whether the Context of the Frame has been canceled, and if
-// so, returns a non-nil error.
-func (fm *Frame) CancelCause() error {
+// Canceled reports whether the Context of the Frame has been canceled.
+func (fm *Frame) Canceled() bool {
 	select {
 	case <-fm.ctx.Done():
-		return context.Cause(fm.ctx)
+		return true
 	default:
-		return nil
+		return false
 	}
 }
 

pkg/eval/glob.go

@@ -253,7 +253,7 @@ func doGlob(ctx context.Context, gp globPattern) ([]any, error) {
 		}
 		return true
 	}) {
-		return nil, context.Cause(ctx)
+		return nil, ErrInterrupted
 	}
 	if len(vs) == 0 && !gp.Flags.Has(noMatchOK) {
 		return nil, ErrWildcardNoMatch

pkg/eval/interrupts.go

@@ -11,15 +11,11 @@ import (
 // ErrInterrupted is thrown when the execution is interrupted by a signal.
 var ErrInterrupted = errors.New("interrupted")
 
-// Used to "cancel" a finished evaluation. It is a bug if this actually cancels
-// anything.
-var errEvalFinished = errors.New("internal bug, eval should have finished")
-
 // ListenInterrupts returns a Context that is canceled when SIGINT or SIGQUIT
 // has been received by the process. It also returns a function to cancel the
 // Context, which should be called when it is no longer needed.
 func ListenInterrupts() (context.Context, func()) {
-	ctx, cancel := context.WithCancelCause(context.Background())
+	ctx, cancel := context.WithCancel(context.Background())
 
 	sigCh := make(chan os.Signal, 1)
 	signal.Notify(sigCh, syscall.SIGINT, syscall.SIGQUIT)
@@ -27,13 +23,13 @@ func ListenInterrupts() (context.Context, func()) {
 	go func() {
 		select {
 		case <-sigCh:
-			cancel(ErrInterrupted)
+			cancel()
 		case <-ctx.Done():
 		}
 		signal.Stop(sigCh)
 	}()
 
 	return ctx, func() {
-		cancel(errEvalFinished)
+		cancel()
 	}
 }