in noImplicitReturns mode, also disallow "return;"

In --noImplicitReturns mode, if a function specifies a return type, disallow empty "return;" statements. Fixes microsoft#5916.

Author: evmar

src/compiler/checker.ts

@@ -13842,11 +13842,11 @@ namespace ts {
  }
  }
 
- if (node.expression) {
-  const func = getContainingFunction(node);
- if (func) {
-  const signature = getSignatureFromDeclaration(func);
-  const returnType = getReturnTypeOfSignature(signature);
+ const func = getContainingFunction(node);
+ if (func) {
+ const signature = getSignatureFromDeclaration(func);
+ const returnType = getReturnTypeOfSignature(signature);
+ if (node.expression) {
  const exprType = checkExpressionCached(node.expression);
 
  if (func.asteriskToken) {
@@ -13881,6 +13881,10 @@ namespace ts {
  }
  }
  }
+ else if (compilerOptions.noImplicitReturns && !maybeTypeOfKind(returnType, TypeFlags.Void | TypeFlags.Any)) {
+ // The function has a return type, but the return statement doesn't have an expression.
+ error(node, Diagnostics.Not_all_code_paths_return_a_value);
+ }
  }
  }
 

tests/baselines/reference/noImplicitReturnsWithoutReturnExpression.errors.txt

@@ -0,0 +1,34 @@
+tests/cases/compiler/noImplicitReturnsWithoutReturnExpression.ts(2,5): error TS7030: Not all code paths return a value.
+tests/cases/compiler/noImplicitReturnsWithoutReturnExpression.ts(22,9): error TS7030: Not all code paths return a value.
+
+
+==== tests/cases/compiler/noImplicitReturnsWithoutReturnExpression.ts (2 errors) ====
+ function isMissingReturnExpression(): number {
+ return;
+ ~~~~~~~
+!!! error TS7030: Not all code paths return a value.
+ }
+ 
+ function isMissingReturnExpression2(): any {
+ return;
+ }
+ 
+ function isMissingReturnExpression3(): number|void {
+ return;
+ }
+ 
+ function isMissingReturnExpression4(): void {
+ return;
+ }
+ 
+ function isMissingReturnExpression5(x) {
+ if (x) {
+ return 0;
+ }
+ else {
+ return;
+ ~~~~~~~
+!!! error TS7030: Not all code paths return a value.
+ }
+ }
+ 

tests/baselines/reference/noImplicitReturnsWithoutReturnExpression.js

@@ -0,0 +1,48 @@
+//// [noImplicitReturnsWithoutReturnExpression.ts]
+function isMissingReturnExpression(): number {
+ return;
+}
+
+function isMissingReturnExpression2(): any {
+ return;
+}
+
+function isMissingReturnExpression3(): number|void {
+ return;
+}
+
+function isMissingReturnExpression4(): void {
+ return;
+}
+
+function isMissingReturnExpression5(x) {
+ if (x) {
+ return 0;
+ }
+ else {
+ return;
+ }
+}
+
+
+//// [noImplicitReturnsWithoutReturnExpression.js]
+function isMissingReturnExpression() {
+ return;
+}
+function isMissingReturnExpression2() {
+ return;
+}
+function isMissingReturnExpression3() {
+ return;
+}
+function isMissingReturnExpression4() {
+ return;
+}
+function isMissingReturnExpression5(x) {
+ if (x) {
+ return 0;
+ }
+ else {
+ return;
+ }
+}

tests/cases/compiler/noImplicitReturnsWithoutReturnExpression.ts

@@ -0,0 +1,25 @@
+// @noImplicitReturns: true
+function isMissingReturnExpression(): number {
+ return;
+}
+
+function isMissingReturnExpression2(): any {
+ return;
+}
+
+function isMissingReturnExpression3(): number|void {
+ return;
+}
+
+function isMissingReturnExpression4(): void {
+ return;
+}
+
+function isMissingReturnExpression5(x) {
+ if (x) {
+ return 0;
+ }
+ else {
+ return;
+ }
+}