[vala/staging] vala: Improve error for incompatible expressions in conditional expression

[Rico Tzschichholz <ricotz src gnome org>]

commit c6142ef5261617095aa06f431bab92f147f53a37
Author: Rico Tzschichholz <ricotz ubuntu com>
Date:   Sun Mar 14 12:38:16 2021 +0100

    vala: Improve error for incompatible expressions in conditional expression

 tests/Makefile.am                                       | 1 +
 tests/semantic/conditional-expression-incompatible.test | 7 +++++++
 vala/valaconditionalexpression.vala                     | 3 ++-
 3 files changed, 10 insertions(+), 1 deletion(-)
---
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 3373316ed..bfbc13dd3 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -934,6 +934,7 @@ TESTS = \
        semantic/class-singleton-non-gobject.test \
        semantic/class-too-few-type-arguments.test \
        semantic/class-too-many-type-arguments.test \
+       semantic/conditional-expression-incompatible.test \
        semantic/conditional-expression-no-block.test \
        semantic/constant-extern.test \
        semantic/constant-pointer.test \
diff --git a/tests/semantic/conditional-expression-incompatible.test 
b/tests/semantic/conditional-expression-incompatible.test
new file mode 100644
index 000000000..1d8c108c3
--- /dev/null
+++ b/tests/semantic/conditional-expression-incompatible.test
@@ -0,0 +1,7 @@
+Invalid Code
+
+void main () {
+       string foo = "foo";
+       int bar = 42;
+       var manam = true ? foo : bar;
+}
diff --git a/vala/valaconditionalexpression.vala b/vala/valaconditionalexpression.vala
index 1bc100081..c8bfdbce1 100644
--- a/vala/valaconditionalexpression.vala
+++ b/vala/valaconditionalexpression.vala
@@ -194,7 +194,8 @@ public class Vala.ConditionalExpression : Expression {
                        value_type = false_expression.value_type.copy ();
                } else {
                        error = true;
-                       Report.error (condition.source_reference, "Incompatible expressions");
+                       var source_reference = new SourceReference (true_expression.source_reference.file, 
true_expression.source_reference.begin, false_expression.source_reference.end);
+                       Report.error (source_reference, "Cannot resolve target type from `%s' and `%s'", 
true_expression.value_type.to_prototype_string (), false_expression.value_type.to_prototype_string ());
                        return false;
                }