Semantic: fix behavior of union and proc notation with untyped expres…

…sion

Fixed crystal-lang#5805

The reason of crystal-lang#5805 is missing to check untyped in union types.
And `ProcNotation` has the same problem. It is fixed also.

spec/compiler/semantic/proc_spec.cr

@@ -880,4 +880,14 @@ describe "Semantic: proc" do
       Foo.new.x
       )) { proc_of(int32) }
   end
+
+  it "does not raise an error if proc notation contains untyped" do
+    assert_type(%(
+      x = 1
+      if x.is_a?(String)
+        [] of typeof(x) ->
+      end
+      x
+      )) { int32 }
+  end
 end

spec/compiler/semantic/union_spec.cr

@@ -165,4 +165,14 @@ describe "Semantic: union" do
       {foo(1), foo("hi")}
       )) { tuple_of([int32, string]) }
   end
+
+  it "does not raise an error if union contains untyped" do
+    assert_type(%(
+      x = 1
+      if x.is_a?(String)
+        [] of typeof(x) | typeof(1)
+      end
+      x
+      )) { int32 }
+  end
 end

src/compiler/crystal/semantic/main_visitor.cr

@@ -286,12 +286,14 @@ module Crystal
       @in_type_args -= 1
 
       if inputs = node.inputs
+        return false unless inputs.all? &.type?
         types = inputs.map &.type.instance_type.virtual_type
       else
         types = [] of Type
       end
 
       if output = node.output
+        return false unless output.type?
         types << output.type.instance_type.virtual_type
       else
         types << program.void
@@ -307,6 +309,8 @@ module Crystal
       node.types.each &.accept self
       @in_type_args -= 1
 
+      return false unless node.types.all? &.type?
+
       old_in_is_a, @in_is_a = @in_is_a, false
 
       types = node.types.map do |subtype|