Add missing bounds check in isReachableFlowNodeWorker

internal/checker/flow.go

@@ -2484,12 +2484,9 @@ func (c *Checker) isReachableFlowNodeWorker(f *FlowState, flow *ast.FlowNode, no
 		case flags&(ast.FlowFlagsAssignment|ast.FlowFlagsCondition|ast.FlowFlagsArrayMutation) != 0:
 			flow = flow.Antecedent
 		case flags&ast.FlowFlagsCall != 0:
-			signature := c.getEffectsSignature(flow.Node)
-			if signature != nil {
-				predicate := c.getTypePredicateOfSignature(signature)
-				if predicate != nil && predicate.kind == TypePredicateKindAssertsIdentifier && predicate.t == nil {
-					predicateArgument := flow.Node.Arguments()[predicate.parameterIndex]
-					if predicateArgument != nil && c.isFalseExpression(predicateArgument) {
+			if signature := c.getEffectsSignature(flow.Node); signature != nil {
+				if predicate := c.getTypePredicateOfSignature(signature); predicate != nil && predicate.kind == TypePredicateKindAssertsIdentifier && predicate.t == nil {
+					if arguments := flow.Node.Arguments(); int(predicate.parameterIndex) < len(arguments) && c.isFalseExpression(arguments[predicate.parameterIndex]) {
 						return false
 					}
 				}

testdata/baselines/reference/compiler/assertionWithNoArgument.symbols

@@ -0,0 +1,15 @@
+//// [tests/cases/compiler/assertionWithNoArgument.ts] ////
+
+=== assertionWithNoArgument.ts ===
+export function assertWeird(value?: string): asserts value {
+>assertWeird : Symbol(assertWeird, Decl(assertionWithNoArgument.ts, 0, 0))
+>value : Symbol(value, Decl(assertionWithNoArgument.ts, 0, 28))
+>value : Symbol(value, Decl(assertionWithNoArgument.ts, 0, 28))
+}
+
+assertWeird();
+>assertWeird : Symbol(assertWeird, Decl(assertionWithNoArgument.ts, 0, 0))
+
+assertWeird("hello");
+>assertWeird : Symbol(assertWeird, Decl(assertionWithNoArgument.ts, 0, 0))
+

testdata/baselines/reference/compiler/assertionWithNoArgument.types

@@ -0,0 +1,17 @@
+//// [tests/cases/compiler/assertionWithNoArgument.ts] ////
+
+=== assertionWithNoArgument.ts ===
+export function assertWeird(value?: string): asserts value {
+>assertWeird : (value?: string | undefined) => asserts value
+>value : string | undefined
+}
+
+assertWeird();
+>assertWeird() : void
+>assertWeird : (value?: string | undefined) => asserts value
+
+assertWeird("hello");
+>assertWeird("hello") : void
+>assertWeird : (value?: string | undefined) => asserts value
+>"hello" : "hello"
+

testdata/tests/cases/compiler/assertionWithNoArgument.ts

@@ -0,0 +1,8 @@
+// @strict: true
+// @noemit: true
+
+export function assertWeird(value?: string): asserts value {
+}
+
+assertWeird();
+assertWeird("hello");