Fixed #4030: Can't catch TypeCastError when doing as inside method

Ary Borenszweig · Ary Borenszweig · commit ced58fcf4492 · 2017-02-14T09:55:56.000-03:00
diff --git a/spec/compiler/codegen/exception_spec.cr b/spec/compiler/codegen/exception_spec.cr
@@ -1255,4 +1255,22 @@ describe "Code gen: exception" do
       print 5
       )).to_i.should eq(123)
   end
+
+  it "catches exception thrown by as inside method (#4030)" do
+    run(%(
+      require "prelude"
+
+      def foo
+        a = 1 || ""
+        a.as(String)
+      end
+
+      begin
+        foo
+        "bad"
+      rescue ex : TypeCastError
+        "good"
+      end
+      )).to_string.should eq("good")
+  end
 end
diff --git a/src/compiler/crystal/semantic/main_visitor.cr b/src/compiler/crystal/semantic/main_visitor.cr
@@ -1696,6 +1696,12 @@ module Crystal
     end
 
     def visit(node : Cast | NilableCast)
+      # If there's an `x.as(T)` inside a method, that method
+      # has a chance to raise, so we must mark it as such
+      if typed_def = @typed_def
+        typed_def.raises = true
+      end
+
       node.obj.accept self
 
       @in_type_args += 1
