checker: add an interface check for mutability, fixes #1081, fixes #7038 (#11963)

vlib/context/README.md

@@ -39,9 +39,9 @@ fn example_with_cancel() {
 	// The callers of gen need to cancel the context once
 	// they are done consuming generated integers not to leak
 	// the internal routine started by gen.
-	gen := fn (ctx context.Context) chan int {
+	gen := fn (mut ctx context.Context) chan int {
 		dst := chan int{}
-		go fn (ctx context.Context, dst chan int) {
+		go fn (mut ctx context.Context, dst chan int) {
 			mut v := 0
 			ch := ctx.done()
 			for {
@@ -55,16 +55,20 @@ fn example_with_cancel() {
 					}
 				}
 			}
-		}(ctx, dst)
+		}(mut ctx, dst)
 		return dst
 	}
 
-	ctx, cancel := context.with_cancel(context.background())
+	mut background := context.background()
+	mut b := &background
+	mut ctx, cancel := context.with_cancel(mut b)
 	defer {
 		cancel()
 	}
 
-	ch := gen(ctx)
+	mut mut_ctx := ctx
+	mut ctx2 := &mut_ctx
+	ch := gen(mut ctx2)
 	for i in 0 .. 5 {
 		v := <-ch
 		assert i == v
@@ -87,7 +91,9 @@ const (
 // function that it should abandon its work as soon as it gets to it.
 fn example_with_deadline() {
 	dur := time.now().add(short_duration)
-	ctx, cancel := context.with_deadline(context.background(), dur)
+	mut background := context.background()
+	mut b := &background
+	mut ctx, cancel := context.with_deadline(mut b, dur)
 
 	defer {
 		// Even though ctx will be expired, it is good practice to call its
@@ -122,7 +128,9 @@ const (
 fn example_with_timeout() {
 	// Pass a context with a timeout to tell a blocking function that it
 	// should abandon its work after the timeout elapses.
-	ctx, cancel := context.with_timeout(context.background(), short_duration)
+	mut background := context.background()
+	mut b := &background
+	mut ctx, cancel := context.with_timeout(mut b, short_duration)
 	defer {
 		cancel()
 	}

vlib/context/_context.v

@@ -43,23 +43,6 @@ pub interface Context {
 	// should be canceled. deadline returns none when no deadline is
 	// set. Successive calls to deadline return the same results.
 	deadline() ?time.Time
-	// done returns a channel that's closed when work done on behalf of this
-	// context should be canceled. done may return nil if this context can
-	// never be canceled. Successive calls to done return the same value.
-	// The close of the done channel may happen asynchronously,
-	// after the cancel function returns.
-	//
-	// with_cancel arranges for done to be closed when cancel is called;
-	// with_deadline arranges for done to be closed when the deadline
-	// expires; with_timeout arranges for done to be closed when the timeout
-	// elapses.
-	done() chan int
-	// If done is not yet closed, err returns nil.
-	// If done is closed, err returns a non-nil error explaining why:
-	// canceled if the context was canceled
-	// or deadline_exceeded if the context's deadline passed.
-	// After err returns a non-nil error, successive calls to err return the same error.
-	err() IError
 	// Value returns the value associated with this context for key, or nil
 	// if no value is associated with key. Successive calls to Value with
 	// the same key returns the same result.
@@ -76,6 +59,24 @@ pub interface Context {
 	// collisions.
 	value(key Key) ?Any
 	str() string
+	// done returns a channel that's closed when work done on behalf of this
+	// context should be canceled. done may return nil if this context can
+	// never be canceled. Successive calls to done return the same value.
+	// The close of the done channel may happen asynchronously,
+	// after the cancel function returns.
+	//
+	// with_cancel arranges for done to be closed when cancel is called;
+	// with_deadline arranges for done to be closed when the deadline
+	// expires; with_timeout arranges for done to be closed when the timeout
+	// elapses.
+mut:
+	done() chan int
+	// If done is not yet closed, err returns nil.
+	// If done is closed, err returns a non-nil error explaining why:
+	// canceled if the context was canceled
+	// or deadline_exceeded if the context's deadline passed.
+	// After err returns a non-nil error, successive calls to err return the same error.
+	err() IError
 }
 
 // background returns an empty Context. It is never canceled, has no

vlib/context/cancel.v

@@ -12,12 +12,13 @@ pub type CancelFn = fn ()
 
 pub interface Canceler {
 	id string
+mut:
 	cancel(remove_from_parent bool, err IError)
 	done() chan int
 }
 
 [deprecated]
-pub fn cancel(ctx Context) {
+pub fn cancel(mut ctx Context) {
 	match mut ctx {
 		CancelContext {
 			ctx.cancel(true, canceled)
@@ -47,9 +48,9 @@ mut:
 //
 // Canceling this context releases resources associated with it, so code should
 // call cancel as soon as the operations running in this Context complete.
-pub fn with_cancel(parent Context) (Context, CancelFn) {
+pub fn with_cancel(mut parent Context) (Context, CancelFn) {
 	mut c := new_cancel_context(parent)
-	propagate_cancel(parent, c)
+	propagate_cancel(mut parent, mut c)
 	return Context(c), fn [mut c] () {
 		c.cancel(true, canceled)
 	}
@@ -116,18 +117,20 @@ fn (mut ctx CancelContext) cancel(remove_from_parent bool, err IError) {
 
 	for _, child in ctx.children {
 		// NOTE: acquiring the child's lock while holding parent's lock.
-		child.cancel(false, err)
+		mut c := child
+		c.cancel(false, err)
 	}
 
 	ctx.children = map[string]Canceler{}
 	ctx.mutex.unlock()
 
 	if remove_from_parent {
-		remove_child(ctx.context, ctx)
+		mut cc := &ctx.context
+		remove_child(mut cc, ctx)
 	}
 }
 
-fn propagate_cancel(parent Context, child Canceler) {
+fn propagate_cancel(mut parent Context, mut child Canceler) {
 	done := parent.done()
 	select {
 		_ := <-done {
@@ -136,15 +139,15 @@ fn propagate_cancel(parent Context, child Canceler) {
 			return
 		}
 	}
-	mut p := parent_cancel_context(parent) or {
-		go fn (parent Context, child Canceler) {
+	mut p := parent_cancel_context(mut parent) or {
+		go fn (mut parent Context, mut child Canceler) {
 			pdone := parent.done()
 			select {
 				_ := <-pdone {
 					child.cancel(false, parent.err())
 				}
 			}
-		}(parent, child)
+		}(mut parent, mut child)
 		return
 	}
 
@@ -162,7 +165,7 @@ fn propagate_cancel(parent Context, child Canceler) {
 // parent.done() matches that CancelContext. (If not, the CancelContext
 // has been wrapped in a custom implementation providing a
 // different done channel, in which case we should not bypass it.)
-fn parent_cancel_context(parent Context) ?&CancelContext {
+fn parent_cancel_context(mut parent Context) ?&CancelContext {
 	done := parent.done()
 	if done.closed {
 		return none
@@ -181,7 +184,7 @@ fn parent_cancel_context(parent Context) ?&CancelContext {
 }
 
 // remove_child removes a context from its parent.
-fn remove_child(parent Context, child Canceler) {
-	mut p := parent_cancel_context(parent) or { return }
+fn remove_child(mut parent Context, child Canceler) {
+	mut p := parent_cancel_context(mut parent) or { return }
 	p.children.delete(child.id)
 }

vlib/context/cancel_test.v

@@ -10,9 +10,9 @@ fn test_with_cancel() {
 	// The callers of gen need to cancel the context once
 	// they are done consuming generated integers not to leak
 	// the internal routine started by gen.
-	gen := fn (ctx context.Context) chan int {
+	gen := fn (mut ctx context.Context) chan int {
 		dst := chan int{}
-		go fn (ctx context.Context, dst chan int) {
+		go fn (mut ctx context.Context, dst chan int) {
 			mut v := 0
 			ch := ctx.done()
 			for {
@@ -26,16 +26,20 @@ fn test_with_cancel() {
 					}
 				}
 			}
-		}(ctx, dst)
+		}(mut ctx, dst)
 		return dst
 	}
 
-	ctx, cancel := context.with_cancel(context.background())
+	mut background := context.background()
+	mut b := &background
+	mut ctx, cancel := context.with_cancel(mut b)
 	defer {
 		cancel()
 	}
 
-	ch := gen(ctx)
+	mut mut_ctx := ctx
+	mut ctx2 := &mut_ctx
+	ch := gen(mut ctx2)
 	for i in 0 .. 5 {
 		v := <-ch
 		assert i == v

vlib/context/deadline.v

@@ -26,12 +26,12 @@ mut:
 //
 // Canceling this context releases resources associated with it, so code should
 // call cancel as soon as the operations running in this Context complete.
-pub fn with_deadline(parent Context, d time.Time) (Context, CancelFn) {
+pub fn with_deadline(mut parent Context, d time.Time) (Context, CancelFn) {
 	id := rand.uuid_v4()
 	if cur := parent.deadline() {
 		if cur < d {
 			// The current deadline is already sooner than the new one.
-			return with_cancel(parent)
+			return with_cancel(mut parent)
 		}
 	}
 	cancel_ctx := new_cancel_context(parent)
@@ -40,7 +40,7 @@ pub fn with_deadline(parent Context, d time.Time) (Context, CancelFn) {
 		deadline: d
 		id: id
 	}
-	propagate_cancel(parent, ctx)
+	propagate_cancel(mut parent, mut ctx)
 	dur := d - time.now()
 	if dur.nanoseconds() <= 0 {
 		ctx.cancel(true, deadline_exceeded) // deadline has already passed
@@ -64,8 +64,8 @@ pub fn with_deadline(parent Context, d time.Time) (Context, CancelFn) {
 //
 // Canceling this context releases resources associated with it, so code should
 // call cancel as soon as the operations running in this Context complete
-pub fn with_timeout(parent Context, timeout time.Duration) (Context, CancelFn) {
-	return with_deadline(parent, time.now().add(timeout))
+pub fn with_timeout(mut parent Context, timeout time.Duration) (Context, CancelFn) {
+	return with_deadline(mut parent, time.now().add(timeout))
 }
 
 pub fn (ctx &TimerContext) deadline() ?time.Time {
@@ -88,7 +88,8 @@ pub fn (mut ctx TimerContext) cancel(remove_from_parent bool, err IError) {
 	ctx.cancel_ctx.cancel(false, err)
 	if remove_from_parent {
 		// Remove this TimerContext from its parent CancelContext's children.
-		remove_child(ctx.cancel_ctx.context, ctx)
+		mut cc := &ctx.cancel_ctx.context
+		remove_child(mut cc, ctx)
 	}
 }
 

vlib/context/deadline_test.v

@@ -10,7 +10,9 @@ const (
 // function that it should abandon its work as soon as it gets to it.
 fn test_with_deadline() {
 	dur := time.now().add(short_duration)
-	ctx, cancel := context.with_deadline(context.background(), dur)
+	mut background := context.background()
+	mut b := &background
+	mut ctx, cancel := context.with_deadline(mut b, dur)
 
 	defer {
 		// Even though ctx will be expired, it is good practice to call its
@@ -33,7 +35,9 @@ fn test_with_deadline() {
 fn test_with_timeout() {
 	// Pass a context with a timeout to tell a blocking function that it
 	// should abandon its work after the timeout elapses.
-	ctx, cancel := context.with_timeout(context.background(), short_duration)
+	mut background := context.background()
+	mut b := &background
+	mut ctx, cancel := context.with_timeout(mut b, short_duration)
 	defer {
 		cancel()
 	}

vlib/context/value.v

@@ -37,11 +37,11 @@ pub fn (ctx &ValueContext) deadline() ?time.Time {
 	return ctx.context.deadline()
 }
 
-pub fn (ctx &ValueContext) done() chan int {
+pub fn (mut ctx ValueContext) done() chan int {
 	return ctx.context.done()
 }
 
-pub fn (ctx &ValueContext) err() IError {
+pub fn (mut ctx ValueContext) err() IError {
 	return ctx.context.err()
 }