From 6d6c620cc2e047047f8aba4eb7fe6acea81d77b4 Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Mon, 16 Sep 2019 15:30:45 -0700
Subject: [PATCH] Report grammatic and type-based unreachable code errors in
 the same way

---
 src/compiler/binder.ts  |  3 +++
 src/compiler/checker.ts | 10 +++++-----
 src/compiler/types.ts   |  4 +++-
 3 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/src/compiler/binder.ts b/src/compiler/binder.ts
index 5006e841dc7..cf93ee17ebd 100644
--- a/src/compiler/binder.ts
+++ b/src/compiler/binder.ts
@@ -672,6 +672,9 @@ namespace ts {
                 bindJSDoc(node);
                 return;
             }
+            if (node.kind >= SyntaxKind.FirstStatement && node.kind <= SyntaxKind.LastStatement) {
+                node.flowNode = currentFlow;
+            }
             switch (node.kind) {
                 case SyntaxKind.WhileStatement:
                     bindWhileStatement(<WhileStatement>node);
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index ba06e08a301..501e6c4d92e 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -17057,11 +17057,7 @@ namespace ts {
             // on empty arrays are possible without implicit any errors and new element types can be inferred without
             // type mismatch errors.
             const resultType = getObjectFlags(evolvedType) & ObjectFlags.EvolvingArray && isEvolvingArrayOperationTarget(reference) ? autoArrayType : finalizeEvolvingArrayType(evolvedType);
-            if (resultType === unreachableNeverType) {
-                error(reference, Diagnostics.Unreachable_code_detected);
-                return declaredType;
-            }
-            if (reference.parent && reference.parent.kind === SyntaxKind.NonNullExpression && getTypeWithFacts(resultType, TypeFacts.NEUndefinedOrNull).flags & TypeFlags.Never) {
+            if (resultType === unreachableNeverType|| reference.parent && reference.parent.kind === SyntaxKind.NonNullExpression && getTypeWithFacts(resultType, TypeFacts.NEUndefinedOrNull).flags & TypeFlags.Never) {
                 return declaredType;
             }
             return resultType;
@@ -30533,6 +30529,10 @@ namespace ts {
                         cancellationToken.throwIfCancellationRequested();
                 }
             }
+            if (kind >= SyntaxKind.FirstStatement && kind <= SyntaxKind.LastStatement &&
+                !compilerOptions.allowUnreachableCode && node.flowNode && !isReachableFlowNode(node.flowNode)) {
+                errorOrSuggestion(compilerOptions.allowUnreachableCode === false, node, Diagnostics.Unreachable_code_detected);
+            }
 
             switch (kind) {
                 case SyntaxKind.TypeParameter:
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index f80126b64c5..afb53aea7a3 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -363,8 +363,8 @@ namespace ts {
         SemicolonClassElement,
         // Element
         Block,
-        VariableStatement,
         EmptyStatement,
+        VariableStatement,
         ExpressionStatement,
         IfStatement,
         DoStatement,
@@ -514,6 +514,8 @@ namespace ts {
         LastTemplateToken = TemplateTail,
         FirstBinaryOperator = LessThanToken,
         LastBinaryOperator = CaretEqualsToken,
+        FirstStatement = VariableStatement,
+        LastStatement = DebuggerStatement,
         FirstNode = QualifiedName,
         FirstJSDocNode = JSDocTypeExpression,
         LastJSDocNode = JSDocPropertyTag,