stmt: Support iterating over vector values

I ran into wanting to iterate over just the values of a vector and wondering
whether that could just work.

This adds support for the following, where v will be value of vec[i].

    local vec = vector("zero", "one", "two");

    for ( i, v in vec )
        print i, v;

NEWS

@@ -96,6 +96,14 @@ New Functionality
   ``disable_analyzer()`` at a later point when it finds the condition due
   to which it vetoed fulfilled (which may be never).
 
+- Add support for iterating over indices and values of a vector using the
+  same syntax as used for iterating over key-value pairs of tables, where
+  ``value`` will be set to ``vec[idx]``.
+
+	local vec = vector("zero", "one", "two");
+	for ( idx, value in vec )
+		print idx, value;
+
 Changed Functionality
 ---------------------
 

src/Stmt.cc

@@ -1290,24 +1290,30 @@ ForStmt::ForStmt(IDPList* arg_loop_vars, ExprPtr loop_expr, IDPtr val_var)
 	{
 	value_var = std::move(val_var);
 
-	if ( e->GetType()->IsTable() )
-		{
-		const auto& yield_type = e->GetType()->AsTableType()->Yield();
+	auto t = e->GetType();
+	zeek::TypePtr yield_type;
 
-		// Verify value_vars type if its already been defined
+	if ( t->IsTable() )
+		yield_type = t->AsTableType()->Yield();
+
+	else if ( t->Tag() == TYPE_VECTOR )
+		yield_type = t->AsVectorType()->Yield();
+
+	else
+		{
+		e->Error("key value for loops only support iteration over tables or vectors");
+		return;
+		}
+
+	// Verify value_vars type if it's already been defined
 	if ( value_var->GetType() )
 		{
 		if ( ! same_type(value_var->GetType(), yield_type) )
 			value_var->GetType()->Error("type clash in iteration", yield_type.get());
 		}
 	else
-			{
 		add_local(value_var, yield_type, INIT_NONE, nullptr, nullptr, VAR_REGULAR);
 	}
-		}
-	else
-		e->Error("key value for loops only support iteration over tables");
-	}
 
 ForStmt::~ForStmt()
 	{
@@ -1358,8 +1364,11 @@ ValPtr ForStmt::DoExec(Frame* f, Val* v, StmtFlowType& flow)
 			if ( ! raw_vv[i] )
 				continue;
 
-			// Set the loop variable to the current index, and make
-			// another pass over the loop body.
+			// Set the loop variable to the current index, the value variable
+			// to the current value, and make another pass over the loop body.
+			if ( value_var )
+				f->SetElement(value_var, vv->ValAt(i));
+
 			f->SetElement((*loop_vars)[0], val_mgr->Count(i));
 			flow = FLOW_NEXT;
 			ret = body->Exec(f, flow);

testing/btest/Baseline/language.vector-for-value/out

@@ -0,0 +1,13 @@
+### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
+0, zero
+1, one
+2, two
+4, four
+0, zero
+1, one
+2, two
+4, four
+zero
+one
+two
+four

testing/btest/language/vector-for-value.zeek

@@ -0,0 +1,20 @@
+# @TEST-EXEC: zeek -b %INPUT >out
+# @TEST-EXEC: btest-diff out
+
+local vec: vector of string = { "zero", "one", "two" };
+vec[4] = "four";
+
+for ( i, v in vec )
+	{
+	print i, v;
+	}
+
+for ( [i], v in vec )
+	{
+	print i, v;
+	}
+
+for ( _, v in vec )
+	{
+	print v;
+	}