Fixed #4242: while and until don't restrict variables after them

crystal-lang · Apr 10, 2017 · b7e048b · b7e048b
1 parent cf207b0
commit b7e048b
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Showing 2 changed files with 74 additions and 8 deletions.
diff --git a/spec/compiler/semantic/while_spec.cr b/spec/compiler/semantic/while_spec.cr
@@ -116,4 +116,49 @@ describe "Semantic: while" do
       x
       )) { union_of(int32, char) }
   end
+
+  it "restricts type after while (#4242)" do
+    assert_type(%(
+      a = nil
+      while a.nil?
+        a = 1
+      end
+      a
+      )) { int32 }
+  end
+
+  it "restricts type after while with not (#4242)" do
+    assert_type(%(
+      a = nil
+      while !a
+        a = 1
+      end
+      a
+      )) { int32 }
+  end
+
+  it "restricts type after while with not and and (#4242)" do
+    assert_type(%(
+      a = nil
+      b = nil
+      while !(a && b)
+        a = 1
+        b = 'a'
+      end
+      {a, b}
+      )) { tuple_of [int32, char] }
+  end
+
+  it "doesn't restrict type after while if there's a break (#4242)" do
+    assert_type(%(
+      a = nil
+      while a.nil?
+        if 1 == 1
+          break
+        end
+        a = 1
+      end
+      a
+      )) { nilable int32 }
+  end
 end
diff --git a/src/compiler/crystal/semantic/main_visitor.cr b/src/compiler/crystal/semantic/main_visitor.cr
@@ -88,6 +88,9 @@ module Crystal
     @or_left_type_filters : TypeFilters?
     @or_right_type_filters : TypeFilters?
 
+    # Type filters for `exp` in `!exp`, used after a `while`
+    @before_not_type_filters : TypeFilters?
+
     def initialize(program, vars = MetaVars.new, @typed_def = nil, meta_vars = nil)
       super(program, vars)
       @while_stack = [] of While
@@ -1977,6 +1980,16 @@ module Crystal
           node.type = program.no_return
           return
         end
+
+        if node.cond.is_a?(Not)
+          after_while_type_filters = @not_type_filters
+        else
+          after_while_type_filters = not_type_filters(node.cond, cond_type_filters)
+        end
+
+        if after_while_type_filters
+          filter_vars(after_while_type_filters)
+        end
       end
 
       node.type = @program.nil
@@ -2849,18 +2862,26 @@ module Crystal
       node.exp.add_observer node
       node.update
 
-      if needs_type_filters? && (type_filters = @type_filters)
-        # `Not` can only deduce type filters for these nodes
-        case exp = node.exp
+      if needs_type_filters?
+        @not_type_filters = @type_filters
+        @type_filters = not_type_filters(node.exp, @type_filters)
+      else
+        @type_filters = nil
+        @not_type_filters = nil
+      end
+
+      false
+    end
+
+    private def not_type_filters(exp, type_filters)
+      if type_filters
+        case exp
         when Var, IsA, RespondsTo, Not
-          @type_filters = type_filters.not
-          return false
+          return type_filters.not
         end
       end
 
-      @type_filters = nil
-
-      false
+      nil
     end
 
     def visit(node : VisibilityModifier)