[vala/staging] Check for assignment to constant

[Rico Tzschichholz <ricotz src gnome org>]

commit 33879ec4c2286314957ac0e03a5a8e89ba6faa02
Author: Simon Werbeck <simon werbeck gmail com>
Date:   Sun Sep 18 18:30:02 2016 +0200

    Check for assignment to constant
    
    This simply checks if the left-hand side is a constant and if so raises
    an error.
    
    Fixes bug 771626

 tests/Makefile.am                |    1 +
 tests/basic-types/bug771626.test |    7 +++++++
 vala/valaassignment.vala         |    6 ++++++
 3 files changed, 14 insertions(+), 0 deletions(-)
---
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 0832a41..b2caa77 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -41,6 +41,7 @@ TESTS = \
        basic-types/bug729907.vala \
        basic-types/bug731017.vala \
        basic-types/bug761307.vala \
+       basic-types/bug771626.test \
        namespaces.vala \
        methods/lambda.vala \
        methods/closures.vala \
diff --git a/tests/basic-types/bug771626.test b/tests/basic-types/bug771626.test
new file mode 100644
index 0000000..64a5da8
--- /dev/null
+++ b/tests/basic-types/bug771626.test
@@ -0,0 +1,7 @@
+Invalid Code
+
+const int FOO = 0;
+
+void main () {
+       FOO = 1;
+}
diff --git a/vala/valaassignment.vala b/vala/valaassignment.vala
index a6b73b9..fc27acf 100644
--- a/vala/valaassignment.vala
+++ b/vala/valaassignment.vala
@@ -145,6 +145,12 @@ public class Vala.Assignment : Expression {
                if (left is MemberAccess) {
                        var ma = (MemberAccess) left;
 
+                       if (ma.symbol_reference is Constant) {
+                               error = true;
+                               Report.error (source_reference, "Assignment to constant after 
initialization");
+                               return false;
+                       }
+
                        if ((!(ma.symbol_reference is Signal || ma.symbol_reference is DynamicProperty) && 
ma.value_type == null) ||
                            (ma.inner == null && ma.member_name == "this" && 
context.analyzer.is_in_instance_method ())) {
                                error = true;