[Parser] error out if there is no block after 'else'

src/parser.cpp

@@ -190,6 +190,9 @@ std::unique_ptr<IfStmt> TheParser::parseIfStmt() {
                                     std::move(trueBranch), std::move(elseIf));
   }
 
+  if (nextToken.kind != TokenKind::Lbrace)
+    return error(nextToken.location, "expected 'else' body");
+
   varOrReturn(falseBlock, parseBlock());
 
   return std::make_unique<IfStmt>(location, std::move(condition),

test/parser/if.al

@@ -0,0 +1,45 @@
+// RUN: compiler %s -ast-dump 2>&1 | filecheck %s
+fn main(): void {
+    // CHECK: [[# @LINE + 1 ]]:8: error: expected expression
+    if {}
+
+    // CHECK: [[# @LINE + 1 ]]:12: error: expected 'if' body
+    if 0.0 ({}
+
+    if 0.0 {}
+    // CHECK: [[# @LINE + 1 ]]:10: error: expected 'else' body
+    else ({}
+
+    if 0.0 {}
+    // CHECK: [[# @LINE + 1 ]]:13: error: expected expression
+    else if {}
+    // CHECK: [[# @LINE + 1 ]]:5: error: expected expression
+    else {}
+
+    if 0.0 {}
+    // CHECK: IfStmt
+    // CHECK-NEXT:   NumberLiteral: '0.0'
+    // CHECK-NEXT:   Block
+
+    if 0.0 {}
+    else {}
+    // CHECK: IfStmt
+    // CHECK-NEXT:   NumberLiteral: '0.0'
+    // CHECK-NEXT:   Block
+    // CHECK-NEXT:   Block
+
+    if 0.0 {}
+    else if 1.0 {}
+    else if 2.0 {}
+    else {}
+    // CHECK: IfStmt
+    // CHECK-NEXT:   NumberLiteral: '0.0'
+    // CHECK-NEXT:   Block
+    // CHECK-NEXT:   IfStmt
+    // CHECK-NEXT:     NumberLiteral: '1.0'
+    // CHECK-NEXT:     Block
+    // CHECK-NEXT:     IfStmt
+    // CHECK-NEXT:       NumberLiteral: '2.0'
+    // CHECK-NEXT:       Block
+    // CHECK-NEXT:       Block
+}