Fix conditional returns messing up nested branches.

Bug: issue #890
Test: new test

compiler/parse-node.cpp

@@ -71,6 +71,17 @@ LogicalExpr::FlattenLogical(int token, std::vector<Expr*>* out)
     }
 }
 
+bool Stmt::IsTerminal() const {
+    switch (flow_type()) {
+        case Flow_Break:
+        case Flow_Continue:
+        case Flow_Return:
+            return true;
+        default:
+            return false;
+    }
+}
+
 BlockStmt*
 BlockStmt::WrapStmt(Stmt* stmt)
 {

compiler/parse-node.h

@@ -118,7 +118,7 @@ class Stmt : public ParseNode
     FlowType flow_type() const { return flow_type_; }
     void set_flow_type(FlowType type) { flow_type_ = type; }
 
-    bool IsTerminal() const { return flow_type() != Flow_None; }
+    bool IsTerminal() const;
 
     StmtKind kind() const { return kind_; }
     bool is(StmtKind k) const { return kind() == k; }

tests/regressions/terminal-statements-in-conditions.out

@@ -0,0 +1 @@
+hi

tests/regressions/terminal-statements-in-conditions.sp

@@ -0,0 +1,18 @@
+#include <shell>
+
+public void main()
+{
+  if (1)
+  {
+    if (0)
+    {
+      return;
+    }
+
+    print("hi\n");
+  }
+  else
+  {
+    print("this should never happen\n");
+  }
+}

tests/regressions/terminal-statements-in-switch.out

@@ -0,0 +1 @@
+hi

tests/regressions/terminal-statements-in-switch.sp

@@ -0,0 +1,30 @@
+#include <shell>
+
+public void main()
+{
+  switch (0)
+  {
+    case 0:
+    {
+      if (0)
+      {
+        return;
+      }
+
+      print("hi\n");
+    }
+    case 1:
+    {
+      if (0)
+      {
+        return;
+      }
+
+      print("this should never happen\n");
+    }
+    default:
+    {
+      print("this should never happen either\n");
+    }
+  }
+}