[vala/staging: 6/10] vala: Report error for yield statements without async context

[Rico Tzschichholz <ricotz src gnome org>]

commit d19187f3b5f7bdc99bba2c9a856f51af9e8cd520
Author: Rico Tzschichholz <ricotz ubuntu com>
Date:   Thu Mar 14 09:16:51 2019 +0100

    vala: Report error for yield statements without async context

 tests/Makefile.am                                         |  1 +
 .../semantic/yield-statement-requires-async-context.test  |  5 +++++
 vala/valayieldstatement.vala                              | 15 +++++++++++++++
 3 files changed, 21 insertions(+)
---
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 41481e7e8..f0000a94b 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -715,6 +715,7 @@ TESTS = \
        semantic/yield-call-requires-async-method.test \
        semantic/yield-creation-requires-async-context.test \
        semantic/yield-creation-requires-async-method.test \
+       semantic/yield-statement-requires-async-context.test \
        $(NULL)
 
 NON_NULL_TESTS = \
diff --git a/tests/semantic/yield-statement-requires-async-context.test 
b/tests/semantic/yield-statement-requires-async-context.test
new file mode 100644
index 000000000..8dd03950b
--- /dev/null
+++ b/tests/semantic/yield-statement-requires-async-context.test
@@ -0,0 +1,5 @@
+Invalid Code
+
+void main () {
+       yield;
+}
diff --git a/vala/valayieldstatement.vala b/vala/valayieldstatement.vala
index 795de2761..91d8e7f9f 100644
--- a/vala/valayieldstatement.vala
+++ b/vala/valayieldstatement.vala
@@ -35,6 +35,21 @@ public class Vala.YieldStatement : CodeNode, Statement {
                this.source_reference = source_reference;
        }
 
+       public override bool check (CodeContext context) {
+               if (checked) {
+                       return !error;
+               }
+
+               checked = true;
+
+               if (context.analyzer.current_method == null || !context.analyzer.current_method.coroutine) {
+                       error = true;
+                       Report.error (source_reference, "yield statement not available outside async method");
+               }
+
+               return !error;
+       }
+
        public override void emit (CodeGenerator codegen) {
                codegen.visit_yield_statement (this);
        }