[vala/staging] vala: Add Block.unreachable_exit and have it set accordingly by FlowAnalyzer

[Rico Tzschichholz <ricotz src gnome org>]

commit b1bf1e999fcfd32dacbc7396dbeda64882272b8a
Author: Rico Tzschichholz <ricotz ubuntu com>
Date:   Thu Feb 4 15:53:55 2021 +0100

    vala: Add Block.unreachable_exit and have it set accordingly by FlowAnalyzer
    
    Use this control flow information in codegen rather than doing an
    educated guess based on occurring ReturnStatement nodes.
    
    See https://gitlab.gnome.org/GNOME/vala/issues/838

 codegen/valaccodebasemodule.vala | 6 +-----
 vala/valablock.vala              | 5 +++++
 vala/valaflowanalyzer.vala       | 2 ++
 3 files changed, 8 insertions(+), 5 deletions(-)
---
diff --git a/codegen/valaccodebasemodule.vala b/codegen/valaccodebasemodule.vala
index 9e46dd2f6..a5c42b01c 100644
--- a/codegen/valaccodebasemodule.vala
+++ b/codegen/valaccodebasemodule.vala
@@ -2404,17 +2404,13 @@ public abstract class Vala.CCodeBaseModule : CodeGenerator {
                        cfile.add_function (unref_fun);
                }
 
-               bool reachable_exit_block = true;
                foreach (Statement stmt in b.get_statements ()) {
-                       if (stmt is ReturnStatement) {
-                               reachable_exit_block = false;
-                       }
                        push_line (stmt.source_reference);
                        stmt.emit (this);
                        pop_line ();
                }
 
-               if (reachable_exit_block) {
+               if (!b.unreachable_exit) {
                        if (b.parent_symbol is Method) {
                                unowned Method m = (Method) b.parent_symbol;
                                // check postconditions
diff --git a/vala/valablock.vala b/vala/valablock.vala
index e13f2b2be..e002909bf 100644
--- a/vala/valablock.vala
+++ b/vala/valablock.vala
@@ -32,6 +32,11 @@ public class Vala.Block : Symbol, Statement {
         */
        public bool contains_jump_statement { get; set; }
 
+       /**
+        * Specifies whether the end of this block is unreachable.
+        */
+       public bool unreachable_exit { get; set; }
+
        public bool captured { get; set; }
 
        private List<Statement> statement_list = new ArrayList<Statement> ();
diff --git a/vala/valaflowanalyzer.vala b/vala/valaflowanalyzer.vala
index a86bda42a..a5a8be993 100644
--- a/vala/valaflowanalyzer.vala
+++ b/vala/valaflowanalyzer.vala
@@ -235,6 +235,8 @@ public class Vala.FlowAnalyzer : CodeVisitor {
                        }
 
                        current_block.connect (m.return_block);
+               } else {
+                       m.body.unreachable_exit = true;
                }
 
                analyze_body (m.entry_block);