check that default clause is non-empty in reachability checks

Author: vladima

src/compiler/binder.ts

@@ -912,8 +912,8 @@ namespace ts {
  preSwitchCaseFlow = currentFlow;
  bind(node.caseBlock);
  addAntecedent(postSwitchLabel, currentFlow);
- const hasDefault = forEach(node.caseBlock.clauses, c => c.kind === SyntaxKind.DefaultClause);
- if (!hasDefault) {
+ const hasNonEmptyDefault = forEach(node.caseBlock.clauses, c => c.kind === SyntaxKind.DefaultClause && c.statements.length);
+ if (!hasNonEmptyDefault) {
  addAntecedent(postSwitchLabel, preSwitchCaseFlow);
  }
  currentBreakTarget = saveBreakTarget;

tests/baselines/reference/reachabilityCheckWithEmptyDefault.js

@@ -0,0 +1,18 @@
+//// [reachabilityCheckWithEmptyDefault.ts]
+declare function print(s: string): void;
+function foo(x: any) {
+switch(x) {
+case 1: return;
+default:
+}
+print('1');
+}
+
+//// [reachabilityCheckWithEmptyDefault.js]
+function foo(x) {
+ switch (x) {
+ case 1: return;
+ default:
+ }
+ print('1');
+}

tests/baselines/reference/reachabilityCheckWithEmptyDefault.symbols

@@ -0,0 +1,18 @@
+=== tests/cases/compiler/reachabilityCheckWithEmptyDefault.ts ===
+declare function print(s: string): void;
+>print : Symbol(print, Decl(reachabilityCheckWithEmptyDefault.ts, 0, 0))
+>s : Symbol(s, Decl(reachabilityCheckWithEmptyDefault.ts, 0, 23))
+
+function foo(x: any) {
+>foo : Symbol(foo, Decl(reachabilityCheckWithEmptyDefault.ts, 0, 40))
+>x : Symbol(x, Decl(reachabilityCheckWithEmptyDefault.ts, 1, 13))
+
+switch(x) {
+>x : Symbol(x, Decl(reachabilityCheckWithEmptyDefault.ts, 1, 13))
+
+case 1: return;
+default:
+}
+print('1');
+>print : Symbol(print, Decl(reachabilityCheckWithEmptyDefault.ts, 0, 0))
+}

tests/baselines/reference/reachabilityCheckWithEmptyDefault.types

@@ -0,0 +1,22 @@
+=== tests/cases/compiler/reachabilityCheckWithEmptyDefault.ts ===
+declare function print(s: string): void;
+>print : (s: string) => void
+>s : string
+
+function foo(x: any) {
+>foo : (x: any) => void
+>x : any
+
+switch(x) {
+>x : any
+
+case 1: return;
+>1 : number
+
+default:
+}
+print('1');
+>print('1') : void
+>print : (s: string) => void
+>'1' : string
+}

tests/cases/compiler/reachabilityCheckWithEmptyDefault.ts

@@ -0,0 +1,8 @@
+declare function print(s: string): void;
+function foo(x: any) {
+switch(x) {
+case 1: return;
+default:
+}
+print('1');
+}