[vala/0.40] vala: Improve check of expression passed to yield

[Rico Tzschichholz <ricotz src gnome org>]

commit 7a2529e63510a0fffa2827a7a11364ec173fca78
Author: Rico Tzschichholz <ricotz ubuntu com>
Date:   Mon Jul 20 10:37:53 2020 +0200

    vala: Improve check of expression passed to yield
    
    Report a proper error and fix codegen cricical when a signal is given:
    
      vala_ccode_function_add_expression: assertion 'expression != NULL' failed
    
    See https://gitlab.gnome.org/GNOME/vala/issues/1039

 tests/Makefile.am                                   |  1 +
 .../yield-call-requires-async-method-2.test         | 12 ++++++++++++
 vala/valamethodcall.vala                            | 21 +++++++++++----------
 3 files changed, 24 insertions(+), 10 deletions(-)
---
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 9de3eb472..ff8d228b1 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -838,6 +838,7 @@ TESTS = \
        semantic/unary-unsupported-negation.test \
        semantic/yield-call-requires-async-context.test \
        semantic/yield-call-requires-async-method.test \
+       semantic/yield-call-requires-async-method-2.test \
        semantic/yield-creation-requires-async-context.test \
        semantic/yield-creation-requires-async-method.test \
        $(NULL)
diff --git a/tests/semantic/yield-call-requires-async-method-2.test 
b/tests/semantic/yield-call-requires-async-method-2.test
new file mode 100644
index 000000000..f3d1fe67d
--- /dev/null
+++ b/tests/semantic/yield-call-requires-async-method-2.test
@@ -0,0 +1,12 @@
+Invalid Code
+
+class Foo {
+       signal void bar ();
+
+       void run () {
+               yield bar ();
+       }
+}
+
+void main () {
+}
diff --git a/vala/valamethodcall.vala b/vala/valamethodcall.vala
index 958254ee5..69dba11ce 100644
--- a/vala/valamethodcall.vala
+++ b/vala/valamethodcall.vala
@@ -475,20 +475,21 @@ public class Vala.MethodCall : Expression {
                formal_value_type = ret_type.copy ();
                value_type = formal_value_type.get_actual_type (target_object_type, method_type_args, this);
 
+               if (is_yield_expression) {
+                       if (!(mtype is MethodType) || !((MethodType) mtype).method_symbol.coroutine) {
+                               error = true;
+                               Report.error (source_reference, "yield expression requires async method");
+                       }
+                       if (context.analyzer.current_method == null || 
!context.analyzer.current_method.coroutine) {
+                               error = true;
+                               Report.error (source_reference, "yield expression not available outside async 
method");
+                       }
+               }
+
                bool may_throw = false;
 
                if (mtype is MethodType) {
                        var m = ((MethodType) mtype).method_symbol;
-                       if (is_yield_expression) {
-                               if (!m.coroutine) {
-                                       error = true;
-                                       Report.error (source_reference, "yield expression requires async 
method");
-                               }
-                               if (context.analyzer.current_method == null || 
!context.analyzer.current_method.coroutine) {
-                                       error = true;
-                                       Report.error (source_reference, "yield expression not available 
outside async method");
-                               }
-                       }
                        if (m != null && m.coroutine && !is_yield_expression && ((MemberAccess) 
call).member_name != "end") {
                                // .begin call of async method, no error can happen here
                        } else {