microsoft · Andarist · Aug 31, 2023 · Nov 13, 2025 · Nov 13, 2025
diff --git a/src/compiler/binder.ts b/src/compiler/binder.ts
@@ -219,6 +219,7 @@ import {
     isSpecialPropertyDeclaration,
     isStatement,
     isStatementButNotDeclaration,
+    isStatementsContainer,
     isStatic,
     isString,
     isStringLiteralLike,
@@ -3850,7 +3851,7 @@ function isEnumDeclarationWithPreservedEmit(node: Node, options: CompilerOptions
 }
 
 function eachUnreachableRange(node: Node, options: CompilerOptions, cb: (start: Node, last: Node) => void): void {
-    if (isStatement(node) && isExecutableStatement(node) && isBlock(node.parent)) {
+    if (isStatement(node) && isExecutableStatement(node) && isStatementsContainer(node.parent)) {
         const { statements } = node.parent;
         const slice = sliceAfter(statements, node);
         getRangesWhere(slice, isExecutableStatement, (start, afterEnd) => cb(slice[start], slice[afterEnd - 1]));

diff --git a/src/compiler/types.ts b/src/compiler/types.ts
@@ -3321,6 +3321,10 @@ export interface Statement extends Node, JSDocContainer {
     _statementBrand: any;
 }
 
+export interface StatementsContainer extends Node {
+    readonly statements: NodeArray<Statement>;
+}
+
 // Represents a statement that is elided as part of a transformation to emit comments on a
 // not-emitted node.
 export interface NotEmittedStatement extends Statement {
@@ -3368,9 +3372,8 @@ export type BlockLike =
     | ModuleBlock
     | CaseOrDefaultClause;
 
-export interface Block extends Statement, LocalsContainer {
+export interface Block extends Statement, LocalsContainer, StatementsContainer {
     readonly kind: SyntaxKind.Block;
-    readonly statements: NodeArray<Statement>;
     /** @internal */ multiLine?: boolean;
 }
 
@@ -3477,18 +3480,16 @@ export interface CaseBlock extends Node, LocalsContainer {
     readonly clauses: NodeArray<CaseOrDefaultClause>;
 }
 
-export interface CaseClause extends Node, JSDocContainer {
+export interface CaseClause extends StatementsContainer, JSDocContainer {
     readonly kind: SyntaxKind.CaseClause;
     readonly parent: CaseBlock;
     readonly expression: Expression;
-    readonly statements: NodeArray<Statement>;
     /** @internal */ fallthroughFlowNode?: FlowNode;
 }
 
-export interface DefaultClause extends Node {
+export interface DefaultClause extends StatementsContainer {
     readonly kind: SyntaxKind.DefaultClause;
     readonly parent: CaseBlock;
-    readonly statements: NodeArray<Statement>;
     /** @internal */ fallthroughFlowNode?: FlowNode;
 }
 
@@ -3653,10 +3654,9 @@ export interface JSDocNamespaceDeclaration extends ModuleDeclaration {
     readonly body?: JSDocNamespaceBody;
 }
 
-export interface ModuleBlock extends Node, Statement {
+export interface ModuleBlock extends StatementsContainer, Statement {
     readonly kind: SyntaxKind.ModuleBlock;
     readonly parent: ModuleDeclaration;
-    readonly statements: NodeArray<Statement>;
 }
 
 export type ModuleReference =
@@ -4316,9 +4316,8 @@ export interface RedirectInfo {
 export type ResolutionMode = ModuleKind.ESNext | ModuleKind.CommonJS | undefined;
 
 // Source files are declarations when they are external modules.
-export interface SourceFile extends Declaration, LocalsContainer {
+export interface SourceFile extends Declaration, LocalsContainer, StatementsContainer {
     readonly kind: SyntaxKind.SourceFile;
-    readonly statements: NodeArray<Statement>;
     readonly endOfFileToken: Token<SyntaxKind.EndOfFileToken>;
 
     fileName: string;

diff --git a/src/compiler/utilities.ts b/src/compiler/utilities.ts
@@ -533,6 +533,7 @@ import {
     startsWith,
     startsWithUseStrict,
     Statement,
+    StatementsContainer,
     StringLiteral,
     StringLiteralLike,
     StringLiteralType,
@@ -4939,6 +4940,19 @@ export function isNodeWithPossibleHoistedDeclaration(node: Node): node is NodeWi
     return false;
 }
 
+/** @internal */
+export function isStatementsContainer(node: Node): node is StatementsContainer {
+    switch (node.kind) {
+        case SyntaxKind.Block:
+        case SyntaxKind.ModuleBlock:
+        case SyntaxKind.SourceFile:
+        case SyntaxKind.DefaultClause:
+        case SyntaxKind.CaseClause:
+            return true;
+    }
+    return false;
+}
+
 /** @internal */
 export type ValueSignatureDeclaration =
     | FunctionDeclaration

diff --git a/tests/baselines/reference/api/typescript.d.ts b/tests/baselines/reference/api/typescript.d.ts
@@ -5271,6 +5271,9 @@ declare namespace ts {
     interface Statement extends Node, JSDocContainer {
         _statementBrand: any;
     }
+    interface StatementsContainer extends Node {
+        readonly statements: NodeArray<Statement>;
+    }
     interface NotEmittedStatement extends Statement {
         readonly kind: SyntaxKind.NotEmittedStatement;
     }
@@ -5295,9 +5298,8 @@ declare namespace ts {
         readonly name?: Identifier;
     }
     type BlockLike = SourceFile | Block | ModuleBlock | CaseOrDefaultClause;
-    interface Block extends Statement, LocalsContainer {
+    interface Block extends Statement, LocalsContainer, StatementsContainer {
         readonly kind: SyntaxKind.Block;
-        readonly statements: NodeArray<Statement>;
     }
     interface VariableStatement extends Statement, FlowContainer {
         readonly kind: SyntaxKind.VariableStatement;
@@ -5373,16 +5375,14 @@ declare namespace ts {
         readonly parent: SwitchStatement;
         readonly clauses: NodeArray<CaseOrDefaultClause>;
     }
-    interface CaseClause extends Node, JSDocContainer {
+    interface CaseClause extends StatementsContainer, JSDocContainer {
         readonly kind: SyntaxKind.CaseClause;
         readonly parent: CaseBlock;
         readonly expression: Expression;
-        readonly statements: NodeArray<Statement>;
     }
-    interface DefaultClause extends Node {
+    interface DefaultClause extends StatementsContainer {
         readonly kind: SyntaxKind.DefaultClause;
         readonly parent: CaseBlock;
-        readonly statements: NodeArray<Statement>;
     }
     type CaseOrDefaultClause = CaseClause | DefaultClause;
     interface LabeledStatement extends Statement, FlowContainer {
@@ -5488,10 +5488,9 @@ declare namespace ts {
         readonly name: Identifier;
         readonly body?: JSDocNamespaceBody;
     }
-    interface ModuleBlock extends Node, Statement {
+    interface ModuleBlock extends StatementsContainer, Statement {
         readonly kind: SyntaxKind.ModuleBlock;
         readonly parent: ModuleDeclaration;
-        readonly statements: NodeArray<Statement>;
     }
     type ModuleReference = EntityName | ExternalModuleReference;
     /**
@@ -5913,9 +5912,8 @@ declare namespace ts {
         getLineAndCharacterOfPosition(pos: number): LineAndCharacter;
     }
     type ResolutionMode = ModuleKind.ESNext | ModuleKind.CommonJS | undefined;
-    interface SourceFile extends Declaration, LocalsContainer {
+    interface SourceFile extends Declaration, LocalsContainer, StatementsContainer {
         readonly kind: SyntaxKind.SourceFile;
-        readonly statements: NodeArray<Statement>;
         readonly endOfFileToken: Token<SyntaxKind.EndOfFileToken>;
         fileName: string;
         text: string;

diff --git a/tests/baselines/reference/reachabilityChecks1.errors.txt b/tests/baselines/reference/reachabilityChecks1.errors.txt
@@ -3,56 +3,88 @@ reachabilityChecks1.ts(6,5): error TS7027: Unreachable code detected.
 reachabilityChecks1.ts(18,5): error TS7027: Unreachable code detected.
 reachabilityChecks1.ts(30,5): error TS7027: Unreachable code detected.
 reachabilityChecks1.ts(47,5): error TS7027: Unreachable code detected.
+reachabilityChecks1.ts(51,1): error TS7027: Unreachable code detected.
 reachabilityChecks1.ts(60,5): error TS7027: Unreachable code detected.
 reachabilityChecks1.ts(69,5): error TS7027: Unreachable code detected.
 
 
-==== reachabilityChecks1.ts (7 errors) ====
+==== reachabilityChecks1.ts (8 errors) ====
     while (true);
     var x = 1;
     ~~~~~~~~~~
-!!! error TS7027: Unreachable code detected.
+    
 
     namespace A {
+    ~~~~~~~~~~~~~
         while (true);
+    ~~~~~~~~~~~~~~~~~
         let x;
+    ~~~~~~~~~~
         ~~~~~~
 !!! error TS7027: Unreachable code detected.
     }
+    ~
+
 
     namespace A1 {
+    ~~~~~~~~~~~~~~
         do {} while(true);
+    ~~~~~~~~~~~~~~~~~~~~~~
         namespace A {
+    ~~~~~~~~~~~~~~~~~
             interface F {}
+    ~~~~~~~~~~~~~~~~~~~~~~
         }
+    ~~~~~
     }
+    ~
+
 
     namespace A2 {
+    ~~~~~~~~~~~~~~
         while (true);
+    ~~~~~~~~~~~~~~~~~
         namespace A {
+    ~~~~~~~~~~~~~~~~~
         ~~~~~~~~~~~~~
             var x = 1;
+    ~~~~~~~~~~~~~~~~~~
     ~~~~~~~~~~~~~~~~~~
         }
     ~~~~~
+    ~~~~~
 !!! error TS7027: Unreachable code detected.
     }
+    ~
+
 
     namespace A3 {
+    ~~~~~~~~~~~~~~
         while (true);
+    ~~~~~~~~~~~~~~~~~
         type T = string;
+    ~~~~~~~~~~~~~~~~~~~~
     }
+    ~
+
 
     namespace A4 {
+    ~~~~~~~~~~~~~~
         while (true);
+    ~~~~~~~~~~~~~~~~~
         namespace A {
+    ~~~~~~~~~~~~~~~~~
         ~~~~~~~~~~~~~
             const enum E { X }
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~
     ~~~~~~~~~~~~~~~~~~~~~~~~~~
         }
     ~~~~~
+    ~~~~~
 !!! error TS7027: Unreachable code detected.
     }
+    ~
+!!! error TS7027: Unreachable code detected.
 
     function f1(x) {
         if (x) {
@@ -74,10 +106,16 @@ reachabilityChecks1.ts(69,5): error TS7027: Unreachable code detected.
     }
 
     namespace B {
+    ~~~~~~~~~~~~~
         for (; ;);
+    ~~~~~~~~~~~~~~
         namespace C {
+    ~~~~~~~~~~~~~~~~~
         }
+    ~~~~~
     }
+    ~
+!!! error TS7027: Unreachable code detected.
 
     function f3() {
         do {

diff --git a/tests/baselines/reference/reachabilityChecks10.errors.txt b/tests/baselines/reference/reachabilityChecks10.errors.txt
@@ -0,0 +1,11 @@
+reachabilityChecks10.ts(2,1): error TS7027: Unreachable code detected.
+
+
+==== reachabilityChecks10.ts (1 errors) ====
+    throw new Error("")
+    console.log("1")
+    ~~~~~~~~~~~~~~~~
+    console.log("2")
+    ~~~~~~~~~~~~~~~~
+!!! error TS7027: Unreachable code detected.
+
diff --git a/tests/baselines/reference/reachabilityChecks10.symbols b/tests/baselines/reference/reachabilityChecks10.symbols
@@ -0,0 +1,16 @@
+//// [tests/cases/compiler/reachabilityChecks10.ts] ////
+
+=== reachabilityChecks10.ts ===
+throw new Error("")
+>Error : Symbol(Error, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+
+console.log("1")
+>console.log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+>console : Symbol(console, Decl(lib.dom.d.ts, --, --))
+>log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+
+console.log("2")
+>console.log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+>console : Symbol(console, Decl(lib.dom.d.ts, --, --))
+>log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+
diff --git a/tests/baselines/reference/reachabilityChecks10.types b/tests/baselines/reference/reachabilityChecks10.types
@@ -0,0 +1,35 @@
+//// [tests/cases/compiler/reachabilityChecks10.ts] ////
+
+=== reachabilityChecks10.ts ===
+throw new Error("")
+>new Error("") : Error
+>              : ^^^^^
+>Error : ErrorConstructor
+>      : ^^^^^^^^^^^^^^^^
+>"" : ""
+>   : ^^
+
+console.log("1")
+>console.log("1") : void
+>                 : ^^^^
+>console.log : (...data: any[]) => void
+>            : ^^^^    ^^     ^^^^^    
+>console : Console
+>        : ^^^^^^^
+>log : (...data: any[]) => void
+>    : ^^^^    ^^     ^^^^^    
+>"1" : "1"
+>    : ^^^
+
+console.log("2")
+>console.log("2") : void
+>                 : ^^^^
+>console.log : (...data: any[]) => void
+>            : ^^^^    ^^     ^^^^^    
+>console : Console
+>        : ^^^^^^^
+>log : (...data: any[]) => void
+>    : ^^^^    ^^     ^^^^^    
+>"2" : "2"
+>    : ^^^
+
diff --git a/tests/baselines/reference/reachabilityChecks9.errors.txt b/tests/baselines/reference/reachabilityChecks9.errors.txt
@@ -0,0 +1,37 @@
+reachabilityChecks9.ts(7,7): error TS7027: Unreachable code detected.
+reachabilityChecks9.ts(20,7): error TS7027: Unreachable code detected.
+
+
+==== reachabilityChecks9.ts (2 errors) ====
+    // https://github.com/microsoft/TypeScript/issues/55562
+
+    function g(str: string) {
+      switch (str) {
+        case "a":
+          return;
+          console.log("1");
+          ~~~~~~~~~~~~~~~~~
+          console.log("2");
+    ~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS7027: Unreachable code detected.
+        case "b":
+          console.log("3");
+      }
+    }
+
+    function h(str: string) {
+      switch (str) {
+        case "a":
+          console.log("1");
+        default:
+          return;
+          console.log("2");
+          ~~~~~~~~~~~~~~~~~
+          console.log("3");
+    ~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS7027: Unreachable code detected.
+        case "b":
+          console.log("4");
+      }
+    }
+