Infer coroutine effects automatically

README.md

@@ -33,7 +33,7 @@ the semantic Type-to-Go mapping turns a class such as `User` into `*User`.
 - Gotlin classes are reference types by default; `*` is only needed for external Go pointer types
 - named external Go struct construction, for example `http.Client(timeout = 3 * time.second)`
 - top-level embedded resources such as `@embed("assets/*") val assets: embed.FS`
-- structured coroutines with `suspend fun`, `runBlocking`, `coroutineScope`, `launch`, `async`, `await`, `delay`, `withTimeout`, and `isActive`
+- inferred structured coroutine effects with `runBlocking`, `coroutineScope`, `launch`, `async`, `await`, `delay`, `withTimeout`, `isActive`, and `coroutineContext`
 
 ## Example
 
@@ -282,8 +282,18 @@ sibling coroutine contexts. The removed `worker`, bare `go`, and channel
 `select` forms are not valid Gotlin syntax; use coroutine scopes, `delay`, and
 explicit channel `read()`/`send()` operations.
 
+Coroutine effects are inferred through the call graph. Functions that directly
+or transitively use coroutine operations receive a hidden scope parameter and
+can only be called from an ambient coroutine scope. `runBlocking` establishes a
+scope boundary, so neither a `suspend` modifier nor manually threaded context is
+needed.
+
+Use `coroutineContext()` only at Go interop boundaries that require a
+`context.Context`; it returns the ambient scope context without exposing it in
+the Gotlin function signature.
+
 ```kotlin
-suspend fun load(): Int {
+fun load(): Int {
     delay(10)
     return 42
 }

cmd/gotlin-lsp/main.go

@@ -1583,40 +1583,41 @@ func builtinHoverDetail(name string) (string, bool) {
 }
 
 var builtinDetails = map[string]string{
-	"println":        "fun println(value: Any): Unit",
+	"println":          "fun println(value: Any): Unit",
-	"runCatching":    "fun runCatching(block: () -> Unit): Result",
+	"runCatching":      "fun runCatching(block: () -> Unit): Result",
-	"Channel":        "fun Channel<T>(capacity: Int = 0): Channel<T>",
+	"Channel":          "fun Channel<T>(capacity: Int = 0): Channel<T>",
-	"listOf":         "fun listOf<T>(values: T...): List<T>",
+	"listOf":           "fun listOf<T>(values: T...): List<T>",
-	"mutableListOf":  "fun mutableListOf<T>(values: T...): MutableList<T>",
+	"mutableListOf":    "fun mutableListOf<T>(values: T...): MutableList<T>",
-	"mapOf":          "fun mapOf<K, V>(pairs: Any...): Map<K, V>",
+	"mapOf":            "fun mapOf<K, V>(pairs: Any...): Map<K, V>",
-	"mutableMapOf":   "fun mutableMapOf<K, V>(pairs: Any...): MutableMap<K, V>",
+	"mutableMapOf":     "fun mutableMapOf<K, V>(pairs: Any...): MutableMap<K, V>",
-	"ByteSlice":      "fun ByteSlice(value: String | Int): ByteSlice",
+	"ByteSlice":        "fun ByteSlice(value: String | Int): ByteSlice",
-	"append":         "fun append<T>(values: List<T>, value: T): List<T>",
+	"append":           "fun append<T>(values: List<T>, value: T): List<T>",
-	"keys":           "fun keys<K, V>(values: Map<K, V>): List<K>",
+	"keys":             "fun keys<K, V>(values: Map<K, V>): List<K>",
-	"goAssert":       "fun goAssert<T>(value: Any): T",
+	"goAssert":         "fun goAssert<T>(value: Any): T",
-	"len":            "fun len(value: Any): Int",
+	"len":              "fun len(value: Any): Int",
-	"cap":            "fun cap(value: Any): Int",
+	"cap":              "fun cap(value: Any): Int",
-	"make":           "fun make<T>(size: Int): T",
+	"make":             "fun make<T>(size: Int): T",
-	"new":            "fun new<T>(): *T",
+	"new":              "fun new<T>(): *T",
-	"copy":           "fun copy(target: Any, source: Any): Int",
+	"copy":             "fun copy(target: Any, source: Any): Int",
-	"delete":         "fun delete(map: Any, key: Any): Unit",
+	"delete":           "fun delete(map: Any, key: Any): Unit",
-	"close":          "fun close(channel: Any): Unit",
+	"close":            "fun close(channel: Any): Unit",
-	"panic":          "fun panic(value: Any): Unit",
+	"panic":            "fun panic(value: Any): Unit",
-	"recover":        "fun recover(): Any",
+	"recover":          "fun recover(): Any",
-	"string":         "fun string(value: Any): String",
+	"string":           "fun string(value: Any): String",
-	"int":            "fun int(value: Any): Int",
+	"int":              "fun int(value: Any): Int",
-	"float64":        "fun float64(value: Any): Double",
+	"float64":          "fun float64(value: Any): Double",
-	"bool":           "fun bool(value: Any): Boolean",
+	"bool":             "fun bool(value: Any): Boolean",
-	"sql":            "typed PostgreSQL query DSL",
+	"sql":              "typed PostgreSQL query DSL",
-	"set":            "fun set(target: Any, value: Any): Unit",
+	"set":              "fun set(target: Any, value: Any): Unit",
-	"now":            "fun now(): time.Time",
+	"now":              "fun now(): time.Time",
-	"runBlocking":    "fun runBlocking(block: suspend () -> Unit): Unit",
+	"runBlocking":      "fun runBlocking(block: () -> Unit): Unit",
-	"coroutineScope": "suspend fun coroutineScope(block: suspend () -> Unit): Unit",
+	"coroutineScope":   "contextual fun coroutineScope(block: () -> Unit): Unit",
-	"launch":         "suspend fun launch(block: suspend () -> Unit): Unit",
+	"launch":           "contextual fun launch(block: () -> Unit): Unit",
-	"async":          "suspend fun async<T>(block: suspend () -> T): Deferred<T>",
+	"async":            "contextual fun async<T>(block: () -> T): Deferred<T>",
-	"delay":          "suspend fun delay(ms: Int): Unit",
+	"delay":            "contextual fun delay(ms: Int): Unit",
-	"withTimeout":    "suspend fun withTimeout(ms: Int, block: suspend () -> Unit): Unit",
+	"withTimeout":      "contextual fun withTimeout(ms: Int, block: () -> Unit): Unit",
-	"isActive":       "suspend fun isActive(): Boolean",
+	"isActive":         "contextual fun isActive(): Boolean",
+	"coroutineContext": "contextual fun coroutineContext(): context.Context",
 }
 
 func contains(values []string, needle string) bool {

internal/lang/ast.go

@@ -65,7 +65,6 @@ type FunctionSignature struct {
 	Params     []Param
 	ReturnType string
 	ReturnRef  TypeRef
-	Suspend    bool
 }
 
 type FunctionDecl struct {
@@ -75,7 +74,6 @@ type FunctionDecl struct {
 	ReturnType string
 	ReturnRef  TypeRef
 	Body       []Stmt
-	Suspend    bool
 }
 
 type Param struct {

internal/lang/coroutines.go

@@ -5,17 +5,17 @@ import (
 	"strings"
 )
 
-var coroutineBuiltins = map[string]bool{"runBlocking": true, "coroutineScope": true, "launch": true, "async": true, "delay": true, "withTimeout": true, "isActive": true}
+var coroutineBuiltins = map[string]bool{"runBlocking": true, "coroutineScope": true, "launch": true, "async": true, "delay": true, "withTimeout": true, "isActive": true, "coroutineContext": true}
 
 func programUsesCoroutines(program *Program) bool {
 	for _, fn := range program.Functions {
-		if fn.Suspend || statementsUseCoroutines(fn.Body) {
+		if statementsUseCoroutines(fn.Body) {
 			return true
 		}
 	}
 	for _, class := range program.Classes {
 		for _, fn := range class.Methods {
-			if fn.Suspend || statementsUseCoroutines(fn.Body) {
+			if statementsUseCoroutines(fn.Body) {
 				return true
 			}
 		}
@@ -94,6 +94,7 @@ func (g *goGenerator) emitCoroutineSupport() {
 	g.line("func (scope *GotlinCoroutineScope) Scope(block func(*GotlinCoroutineScope)) { child:=gotlinNewCoroutineScope(scope.ctx); defer child.cancel(); defer func(){if value:=recover();value!=nil{child.cancel();child.workers.Wait();panic(value)}}(); block(child); child.wait() }")
 	g.line("func (scope *GotlinCoroutineScope) Delay(ms int) { timer:=time.NewTimer(time.Duration(ms)*time.Millisecond); defer timer.Stop(); select { case <-timer.C: case <-scope.ctx.Done(): panic(scope.ctx.Err()) } }")
 	g.line("func (scope *GotlinCoroutineScope) IsActive() bool { return scope.ctx.Err()==nil }")
+	g.line("func (scope *GotlinCoroutineScope) Context() context.Context { return scope.ctx }")
 	g.line("func (scope *GotlinCoroutineScope) WithTimeout(ms int, block func(*GotlinCoroutineScope)) { ctx,cancel:=context.WithTimeout(scope.ctx,time.Duration(ms)*time.Millisecond); defer cancel(); child:=gotlinNewCoroutineScope(ctx); defer child.cancel(); block(child); child.wait() }")
 	g.line("func gotlinRunBlocking(block func(*GotlinCoroutineScope)) { scope:=gotlinNewCoroutineScope(context.Background()); defer scope.cancel(); defer func(){if value:=recover();value!=nil{scope.cancel();scope.workers.Wait();panic(value)}}(); block(scope); scope.wait() }")
 	g.line("type GotlinDeferred[T any] struct { done chan struct{}; value T; failure any }")

internal/lang/coroutines_test.go

@@ -7,7 +7,7 @@ import (
 
 func TestGenerateStructuredCoroutines(t *testing.T) {
 	prog, err := Parse(`package demo
-suspend fun load(): Int { delay(1); return 42 }
+fun load(): Int { delay(1); return 42 }
 fun main() {
     runBlocking {
         coroutineScope {
@@ -31,16 +31,35 @@ fun main() {
 	}
 }
 
-func TestSuspendFunctionRequiresScope(t *testing.T) {
+func TestInferredCoroutineFunctionRequiresScope(t *testing.T) {
 	prog, err := Parse(`package demo
-suspend fun load(): Int { return 1 }
+fun load(): Int { delay(1); return 1 }
 fun main() { println(load()) }`)
 	if err != nil {
 		t.Fatal(err)
 	}
-	_, err = GenerateGo(prog)
+	out, err := GenerateGo(prog)
-	if err == nil || !strings.Contains(err.Error(), "requires a coroutine scope") {
+	if err == nil || !strings.Contains(err.Error(), "contextual function main requires a runBlocking boundary") {
-		t.Fatalf("unexpected error: %v", err)
+		t.Fatalf("unexpected error: %v\n%s", err, out)
+	}
+}
+
+func TestCoroutineEffectPropagatesTransitively(t *testing.T) {
+	prog, err := Parse(`package demo
+fun load(): Int { delay(1); return 42 }
+fun wrapped(): Int { return load() }
+fun main() { runBlocking { println(wrapped()) } }`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	out, err := GenerateGo(prog)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, expected := range []string{"func load(gotlinScope *GotlinCoroutineScope)", "func wrapped(gotlinScope *GotlinCoroutineScope)", "wrapped(gotlinScope)"} {
+		if !strings.Contains(string(out), expected) {
+			t.Fatalf("missing %q:\n%s", expected, out)
+		}
 	}
 }
 
@@ -52,6 +71,51 @@ func TestLegacyConcurrencySyntaxIsRemoved(t *testing.T) {
 	}
 }
 
+func TestSuspendModifierIsRemoved(t *testing.T) {
+	if _, err := Parse(`package demo suspend fun load() {}`); err == nil {
+		t.Fatal("suspend modifier parsed")
+	}
+}
+
+func TestAnalyzeInfersCoroutineEffects(t *testing.T) {
+	program, err := Parse(`package demo
+fun direct() { delay(1) }
+fun transitive() { direct() }
+fun boundary() { runBlocking { transitive() } }`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	semantic, err := Analyze(program)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !semantic.FunctionEffects["direct"].Has(CoroutineEffect) || !semantic.FunctionEffects["transitive"].Has(CoroutineEffect) {
+		t.Fatalf("effects were not propagated: %#v", semantic.FunctionEffects)
+	}
+	if semantic.FunctionEffects["boundary"].Has(CoroutineEffect) {
+		t.Fatalf("runBlocking did not stop effect propagation: %#v", semantic.FunctionEffects)
+	}
+}
+
+func TestCoroutineContextUsesAmbientScope(t *testing.T) {
+	program, err := Parse(`package demo
+import fmt
+fun useContext() { fmt.sprint(coroutineContext()) }
+fun main() { runBlocking { useContext() } }`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	output, err := GenerateGo(program)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, expected := range []string{"func useContext(gotlinScope *GotlinCoroutineScope)", "gotlinScope.Context()", "useContext(gotlinScope)"} {
+		if !strings.Contains(string(output), expected) {
+			t.Fatalf("missing %q:\n%s", expected, output)
+		}
+	}
+}
+
 func TestRunBlockingCancelsAndJoinsChildrenOnPanic(t *testing.T) {
 	prog, err := Parse(`package demo fun main() { runBlocking { launch { delay(1) }; panic("failed") } }`)
 	if err != nil {

internal/lang/effects.go

@@ -0,0 +1,155 @@
+package lang
+
+type Effect uint8
+
+const (
+	NoEffect        Effect = 0
+	CoroutineEffect Effect = 1 << 0
+)
+
+func (effect Effect) Has(required Effect) bool { return effect&required != 0 }
+
+type effectNode struct {
+	key     string
+	symbol  *Symbol
+	direct  Effect
+	callees []*Symbol
+}
+
+func inferCoroutineEffects(semantic *SemanticProgram) {
+	var nodes []*effectNode
+	for index := range semantic.Syntax.Functions {
+		decl := &semantic.Syntax.Functions[index]
+		symbol, _ := semantic.Global.Lookup(decl.Name)
+		node := &effectNode{key: decl.Name, symbol: symbol}
+		collectFunctionEffects(decl.Body, node)
+		nodes = append(nodes, node)
+	}
+	for classIndex := range semantic.Syntax.Classes {
+		class := &semantic.Syntax.Classes[classIndex]
+		classSymbol := semantic.ClassInfo[class.Name]
+		for methodIndex := range class.Methods {
+			method := &class.Methods[methodIndex]
+			node := &effectNode{key: class.Name + "." + method.Name, symbol: classSymbol.Methods[method.Name]}
+			collectFunctionEffects(method.Body, node)
+			nodes = append(nodes, node)
+		}
+	}
+	changed := true
+	for changed {
+		changed = false
+		for _, node := range nodes {
+			effects := node.direct
+			for _, callee := range node.callees {
+				effects |= callee.Effects
+			}
+			if node.symbol != nil && node.symbol.Effects != effects {
+				node.symbol.Effects = effects
+				changed = true
+			}
+		}
+	}
+	for _, node := range nodes {
+		if node.symbol != nil {
+			semantic.FunctionEffects[node.key] = node.symbol.Effects
+			if function, ok := node.symbol.Type.(FunctionType); ok {
+				function.Effects = node.symbol.Effects
+				node.symbol.Type = function
+			}
+		}
+	}
+}
+
+func collectFunctionEffects(statements []Stmt, node *effectNode) {
+	for _, statement := range statements {
+		switch value := statement.(type) {
+		case VarDecl:
+			collectExpressionEffects(value.Value, node)
+		case MultiVarDecl:
+			collectExpressionEffects(value.Value, node)
+		case AssignStmt:
+			collectExpressionEffects(value.Value, node)
+		case AddAssignStmt:
+			collectExpressionEffects(value.Value, node)
+		case MultiAssignStmt:
+			collectExpressionEffects(value.Value, node)
+		case ReturnStmt:
+			if value.Value != nil {
+				collectExpressionEffects(value.Value, node)
+			}
+		case ThrowStmt:
+			collectExpressionEffects(value.Value, node)
+		case DeferStmt:
+			collectExpressionEffects(value.Value, node)
+		case ExprStmt:
+			collectExpressionEffects(value.Value, node)
+		case IfStmt:
+			collectExpressionEffects(value.Cond, node)
+			collectFunctionEffects(value.Then, node)
+			collectFunctionEffects(value.Else, node)
+		case WhileStmt:
+			collectExpressionEffects(value.Cond, node)
+			collectFunctionEffects(value.Body, node)
+		case ForEachStmt:
+			collectExpressionEffects(value.Source, node)
+			collectFunctionEffects(value.Body, node)
+		case MatchStmt:
+			collectExpressionEffects(value.Value, node)
+			for _, matchCase := range value.Cases {
+				collectFunctionEffects(matchCase.Body, node)
+			}
+		case TryCatchStmt:
+			collectFunctionEffects(value.TryBody, node)
+			collectFunctionEffects(value.CatchBody, node)
+		}
+	}
+}
+
+func collectExpressionEffects(expression Expr, node *effectNode) {
+	switch value := expression.(type) {
+	case CallExpr:
+		if ident, ok := value.Callee.(IdentExpr); ok {
+			if ident.Name == "runBlocking" {
+				return
+			}
+			if coroutineBuiltins[ident.Name] {
+				node.direct |= CoroutineEffect
+			}
+		}
+		if semantic := exprMeta(value); semantic != nil {
+			if call, ok := semantic.Node.(HIRGotlinCall); ok && call.Target != nil {
+				node.callees = append(node.callees, call.Target)
+			}
+		}
+		collectExpressionEffects(value.Callee, node)
+		for _, argument := range value.Args {
+			collectExpressionEffects(argument, node)
+		}
+		for _, argument := range value.NamedArgs {
+			collectExpressionEffects(argument.Value, node)
+		}
+	case UnaryExpr:
+		collectExpressionEffects(value.Value, node)
+	case NonNullExpr:
+		collectExpressionEffects(value.Value, node)
+	case TryExpr:
+		collectExpressionEffects(value.Value, node)
+	case BinaryExpr:
+		collectExpressionEffects(value.Left, node)
+		collectExpressionEffects(value.Right, node)
+	case SelectorExpr:
+		collectExpressionEffects(value.Receiver, node)
+	case SafeSelectorExpr:
+		collectExpressionEffects(value.Receiver, node)
+	case IndexExpr:
+		collectExpressionEffects(value.Receiver, node)
+		collectExpressionEffects(value.Index, node)
+	case MatchExpr:
+		collectExpressionEffects(value.Value, node)
+		for _, matchCase := range value.Cases {
+			collectExpressionEffects(matchCase.Value, node)
+		}
+	case LambdaExpr:
+		collectFunctionEffects(value.Body, node)
+	}
+}

internal/lang/generate_go.go

@@ -251,7 +251,11 @@ func (g *goGenerator) function(fn FunctionDecl) error {
 	g.currentClass = nil
 	g.currentFunc = fn
 	previousScope := g.currentCoroutineScope
-	if fn.Suspend {
+	hasCoroutineEffect := g.hasCoroutineEffect(fn)
+	if hasCoroutineEffect && fn.Name == "main" {
+		return fmt.Errorf("contextual function main requires a runBlocking boundary")
+	}
+	if hasCoroutineEffect {
 		g.currentCoroutineScope = "gotlinScope"
 	}
 	defer func() { g.currentCoroutineScope = previousScope }()
@@ -284,11 +288,7 @@ func (g *goGenerator) interfaceDecl(decl InterfaceDecl) {
 	g.line("type " + decl.Name + " interface {")
 	g.indentLevel++
 	for _, method := range decl.Methods {
-		prefix := ""
+		g.line(method.Name + g.renderGoParamsWithPrefix(method.Params, "") + g.renderGoReturnSuffix(method.ReturnType))
-		if method.Suspend {
-			prefix = "gotlinScope *GotlinCoroutineScope"
-		}
-		g.line(method.Name + g.renderGoParamsWithPrefix(method.Params, prefix) + g.renderGoReturnSuffix(method.ReturnType))
 	}
 	g.indentLevel--
 	g.line("}")
@@ -416,7 +416,7 @@ func (g *goGenerator) method(class ClassDecl, fn FunctionDecl) error {
 	g.currentClass = &class
 	g.currentFunc = fn
 	previousScope := g.currentCoroutineScope
-	if fn.Suspend {
+	if g.hasCoroutineEffect(fn) {
 		g.currentCoroutineScope = "gotlinScope"
 	}
 	defer func() { g.currentCoroutineScope = previousScope }()
@@ -954,6 +954,11 @@ func (g *goGenerator) expr(expr Expr, expectedType string) (string, error) {
 					return "", fmt.Errorf("isActive requires a coroutine scope")
 				}
 				return g.currentCoroutineScope + ".IsActive()", nil
+			case "coroutineContext":
+				if g.currentCoroutineScope == "" {
+					return "", fmt.Errorf("coroutineContext requires a coroutine scope")
+				}
+				return g.currentCoroutineScope + ".Context()", nil
 			}
 		}
 		if selector, ok := e.Callee.(SelectorExpr); ok && selector.Name == "await" && len(e.Args) == 0 {
@@ -1197,27 +1202,14 @@ func (g *goGenerator) expr(expr Expr, expectedType string) (string, error) {
 				return fmt.Sprintf("New%s%s(%s)", ident.Name, g.renderCallTypeArguments(e.TypeArgs), strings.Join(args, ", ")), nil
 			}
 		}
-		if ident, ok := e.Callee.(IdentExpr); ok {
+		if resolvedCall != nil {
-			if fn, found := g.semantic.Functions[ident.Name]; found && fn.Suspend {
+			if call, ok := resolvedCall.Node.(HIRGotlinCall); ok && call.Target != nil && call.Target.Effects.Has(CoroutineEffect) {
 				if g.currentCoroutineScope == "" {
-					return "", fmt.Errorf("suspend function %s requires a coroutine scope", ident.Name)
+					return "", fmt.Errorf("contextual function %s requires a coroutine scope", call.Target.Name)
 				}
 				args = append([]string{g.currentCoroutineScope}, args...)
 			}
 		}
-		if selector, ok := e.Callee.(SelectorExpr); ok {
-			if class, found := g.classForType(g.exprType(selector.Receiver)); found {
-				for _, method := range class.Methods {
-					if method.Name == selector.Name && method.Suspend {
-						if g.currentCoroutineScope == "" {
-							return "", fmt.Errorf("suspend method %s requires a coroutine scope", selector.Name)
-						}
-						args = append([]string{g.currentCoroutineScope}, args...)
-						break
-					}
-				}
-			}
-		}
 		callee, err := g.expr(e.Callee, "")
 		if err != nil {
 			return "", err
@@ -2491,12 +2483,20 @@ func (g *goGenerator) cloneScopes() []map[string]bool {
 
 func (g *goGenerator) renderGoFunctionParams(function FunctionDecl) string {
 	prefix := ""
-	if function.Suspend {
+	if g.hasCoroutineEffect(function) {
 		prefix = "gotlinScope *GotlinCoroutineScope"
 	}
 	return g.renderGoParamsWithPrefix(function.Params, prefix)
 }
 
+func (g *goGenerator) hasCoroutineEffect(function FunctionDecl) bool {
+	key := function.Name
+	if g.currentClass != nil {
+		key = g.currentClass.Name + "." + function.Name
+	}
+	return g.semantic.FunctionEffects[key].Has(CoroutineEffect)
+}
+
 func renderGoTypeParameters(params []string) string {
 	if len(params) == 0 {
 		return ""

internal/lang/hir.go

@@ -600,6 +600,11 @@ func (resolver *semanticResolver) meaning(expr Expr, scope *Scope) (ExprMeaning,
 			if root, ok := selectorRootAlias(selector); ok && resolver.program.Imports[root] {
 				return GoCallExpr, nil
 			}
+			if class, _ := classInstance(ResolvedType(selector.Receiver)); class != nil {
+				if method, ok := class.Methods[selector.Name]; ok {
+					return MethodCallExpr, method
+				}
+			}
 			receiverType := ResolvedType(selector.Receiver)
 			if !isUnknownType(resolver.program.goMethodType(receiverType, selector.Name)) {
 				return GoCallExpr, nil
@@ -755,7 +760,7 @@ var semanticBuiltins = map[string]bool{
 	"panic": true, "recover": true, "string": true, "int": true, "float64": true, "bool": true,
 	"sql": true, "set": true, "now": true, "Result": true, "ByteSlice": true,
 	"runBlocking": true, "coroutineScope": true, "launch": true, "async": true,
-	"delay": true, "withTimeout": true, "isActive": true,
+	"delay": true, "withTimeout": true, "isActive": true, "coroutineContext": true,
 	"continue": true, "break": true,
 }
 

internal/lang/parser.go

@@ -138,7 +138,7 @@ func (p *parser) parseProgram() (*Program, error) {
 			default:
 				return nil, fmt.Errorf("unsupported annotation %q", annotation.lexeme)
 			}
-		case p.check(tokenFun) || p.check(tokenSuspend):
+		case p.check(tokenFun):
 			fn, err := p.parseFunction()
 			if err != nil {
 				return nil, err
@@ -325,7 +325,7 @@ func (p *parser) parseClass() (ClassDecl, error) {
 	var methods []FunctionDecl
 	for !p.check(tokenRBrace) && !p.check(tokenEOF) {
 		p.match(tokenOverride)
-		if !p.check(tokenFun) && !p.check(tokenSuspend) {
+		if !p.check(tokenFun) {
 			tok := p.peek()
 			return ClassDecl{}, fmt.Errorf("expected class member at %d, found %q", tok.pos, tok.lexeme)
 		}
@@ -482,12 +482,10 @@ func (p *parser) parseFunction() (FunctionDecl, error) {
 		Params:     signature.Params,
 		ReturnType: signature.ReturnType,
 		Body:       body,
-		Suspend:    signature.Suspend,
 	}, nil
 }
 
 func (p *parser) parseFunctionSignature() (FunctionSignature, error) {
-	suspend := p.match(tokenSuspend)
 	if _, err := p.expect(tokenFun, "expected 'fun'"); err != nil {
 		return FunctionSignature{}, err
 	}
@@ -524,7 +522,6 @@ func (p *parser) parseFunctionSignature() (FunctionSignature, error) {
 		TypeParams: typeParams,
 		Params:     params,
 		ReturnType: returnType,
-		Suspend:    suspend,
 	}, nil
 }
 

internal/lang/symbols.go

@@ -21,6 +21,7 @@ type Symbol struct {
 	Type    Type
 	Mutable bool
 	Decl    any
+	Effects Effect
 }
 
 type Scope struct {
@@ -56,17 +57,18 @@ type ClassSymbol struct {
 }
 
 type SemanticProgram struct {
-	Syntax      *Program
+	Syntax          *Program
-	Global      *Scope
+	Global          *Scope
-	Classes     map[string]ClassDecl
+	Classes         map[string]ClassDecl
-	ClassInfo   map[string]*ClassSymbol
+	ClassInfo       map[string]*ClassSymbol
-	Functions   map[string]FunctionDecl
+	Functions       map[string]FunctionDecl
-	Enums       map[string]EnumDecl
+	Enums           map[string]EnumDecl
-	Imports     map[string]bool
+	Imports         map[string]bool
-	GoPackages  map[string]*gotypes.Package
+	GoPackages      map[string]*gotypes.Package
-	HIR         *HIRProgram
+	HIR             *HIRProgram
-	Mappings    *mappingState
+	Mappings        *mappingState
-	Diagnostics []SemanticDiagnostic
+	Diagnostics     []SemanticDiagnostic
+	FunctionEffects map[string]Effect
 }
 
 func Analyze(program *Program) (*SemanticProgram, error) {
@@ -91,15 +93,16 @@ func AnalyzeWithContext(program *Program, additional []*Program) (*SemanticProgr
 
 func analyzeProgram(program *Program, additional []*Program) (*SemanticProgram, error) {
 	semantic := &SemanticProgram{
-		Syntax:     program,
+		Syntax:          program,
-		Global:     NewScope(nil),
+		Global:          NewScope(nil),
-		Classes:    map[string]ClassDecl{},
+		Classes:         map[string]ClassDecl{},
-		ClassInfo:  map[string]*ClassSymbol{},
+		ClassInfo:       map[string]*ClassSymbol{},
-		Functions:  map[string]FunctionDecl{},
+		Functions:       map[string]FunctionDecl{},
-		Enums:      map[string]EnumDecl{},
+		Enums:           map[string]EnumDecl{},
-		Imports:    map[string]bool{},
+		Imports:         map[string]bool{},
-		GoPackages: map[string]*gotypes.Package{},
+		GoPackages:      map[string]*gotypes.Package{},
-		Mappings:   &mappingState{functions: map[string]string{}},
+		Mappings:        &mappingState{functions: map[string]string{}},
+		FunctionEffects: map[string]Effect{},
 	}
 	programs := append([]*Program{program}, additional...)
 	for _, source := range programs {
@@ -198,6 +201,7 @@ func analyzeProgram(program *Program, additional []*Program) (*SemanticProgram,
 	if err := resolver.resolve(); err != nil {
 		return nil, err
 	}
+	inferCoroutineEffects(semantic)
 	return semantic, nil
 }
 

internal/lang/token.go

@@ -19,7 +19,6 @@ const (
 	tokenEnum       tokenKind = "ENUM"
 	tokenMatch      tokenKind = "MATCH"
 	tokenFun        tokenKind = "FUN"
-	tokenSuspend    tokenKind = "SUSPEND"
 	tokenOverride   tokenKind = "OVERRIDE"
 	tokenPrivate    tokenKind = "PRIVATE"
 	tokenVal        tokenKind = "VAL"
@@ -70,7 +69,6 @@ const (
 
 var keywords = map[string]tokenKind{
 	"fun":       tokenFun,
-	"suspend":   tokenSuspend,
 	"import":    tokenImport,
 	"package":   tokenPackage,
 	"class":     tokenClass,

internal/lang/type_checker.go

@@ -125,6 +125,8 @@ func (semantic *SemanticProgram) TypeOf(expr Expr, environment TypeEnvironment)
 				if len(value.TypeArgs) == 1 {
 					return GenericType{Base: NamedType{Name: "Deferred"}, Args: []Type{resolve(value.TypeArgs[0])}}
 				}
+			case "coroutineContext":
+				return NamedType{Name: "context.Context"}
 			}
 			if ident.Name == "keys" && len(value.Args) == 1 {
 				if mapping, ok := semantic.TypeOf(value.Args[0], environment).(GenericType); ok && (mapping.Base.String() == "Map" || mapping.Base.String() == "MutableMap") && len(mapping.Args) == 2 {

internal/lang/types.go

@@ -57,6 +57,7 @@ type FunctionType struct {
 	TypeParams []string
 	Params     []Type
 	Result     Type
+	Effects    Effect
 }
 
 func (FunctionType) typeNode() {}
@@ -200,7 +201,7 @@ func resolveTypeParameters(typ Type, params map[string]bool) Type {
 		for index, param := range value.Params {
 			resolved[index] = resolveTypeParameters(param, params)
 		}
-		return FunctionType{TypeParams: value.TypeParams, Params: resolved, Result: resolveTypeParameters(value.Result, params)}
+		return FunctionType{TypeParams: value.TypeParams, Params: resolved, Result: resolveTypeParameters(value.Result, params), Effects: value.Effects}
 	case GenericType:
 		args := make([]Type, len(value.Args))
 		for index, arg := range value.Args {
@@ -248,7 +249,7 @@ func substituteType(typ Type, bindings map[string]Type) Type {
 		for index, param := range value.Params {
 			params[index] = substituteType(param, bindings)
 		}
-		return FunctionType{TypeParams: value.TypeParams, Params: params, Result: substituteType(value.Result, bindings)}
+		return FunctionType{TypeParams: value.TypeParams, Params: params, Result: substituteType(value.Result, bindings), Effects: value.Effects}
 	default:
 		return typ
 	}

tools/vscode-gotlin/scripts/validate.js

@@ -42,7 +42,7 @@ assert(language.folding?.markers?.start && language.indentationRules?.increaseIn
 
 const grammarSource = JSON.stringify(grammar);
 const expectedTokens = [
-  "data", "class", "suspend", "private", "override", "val", "var", "if", "else",
+  "data", "class", "private", "override", "val", "var", "if", "else",
   "while", "for", "in", "return", "defer", "try", "catch",
   "throw", "enum", "match", "package", "import", "jsonNaming", "embed", "table", "column", "id",
   "generated", "Int", "Long", "String", "Boolean", "Unit", "Double", "Float", "Any",

tools/vscode-gotlin/syntaxes/gotlin.tmLanguage.json

@@ -254,7 +254,7 @@
       "patterns": [
         {
           "name": "keyword.control.declaration.gotlin",
-          "match": "\\b(package|import|data|class|interface|enum|suspend|fun)\\b"
+          "match": "\\b(package|import|data|class|interface|enum|fun)\\b"
         },
         {
           "name": "storage.modifier.gotlin",