diff --git a/spec/compiler/parser/parser_spec.cr b/spec/compiler/parser/parser_spec.cr
index 22e9c5feb385..f719e5c41b06 100644
--- a/spec/compiler/parser/parser_spec.cr
+++ b/spec/compiler/parser/parser_spec.cr
@@ -204,6 +204,8 @@ module Crystal
 
     it_parses "a = 1", Assign.new("a".var, 1.int32)
     it_parses "a = b = 2", Assign.new("a".var, Assign.new("b".var, 2.int32))
+    it_parses "a[] = 1", Call.new("a".call, "[]=", 1.int32)
+    it_parses "a.[] = 1", Call.new("a".call, "[]=", 1.int32)
 
     it_parses "a, b = 1, 2", MultiAssign.new(["a".var, "b".var] of ASTNode, [1.int32, 2.int32] of ASTNode)
     it_parses "a, b = 1", MultiAssign.new(["a".var, "b".var] of ASTNode, [1.int32] of ASTNode)
@@ -276,6 +278,10 @@ module Crystal
     assert_syntax_error "a.b() += 1"
     assert_syntax_error "a.[]() += 1"
 
+    assert_syntax_error "a.[] 0 = 1"
+    assert_syntax_error "a.[] 0 += 1"
+    assert_syntax_error "a b: 0 = 1"
+
     it_parses "def foo\n1\nend", Def.new("foo", body: 1.int32)
     it_parses "def downto(n)\n1\nend", Def.new("downto", ["n".arg], 1.int32)
     it_parses "def foo ; 1 ; end", Def.new("foo", body: 1.int32)
@@ -524,11 +530,15 @@ module Crystal
     it_parses "foo &.+(2)", Call.new(nil, "foo", block: Block.new([Var.new("__arg0")], Call.new(Var.new("__arg0"), "+", 2.int32)))
     it_parses "foo &.bar.baz", Call.new(nil, "foo", block: Block.new([Var.new("__arg0")], Call.new(Call.new(Var.new("__arg0"), "bar"), "baz")))
     it_parses "foo(&.bar.baz)", Call.new(nil, "foo", block: Block.new([Var.new("__arg0")], Call.new(Call.new(Var.new("__arg0"), "bar"), "baz")))
+    it_parses "foo &.block[]", Call.new(nil, "foo", block: Block.new([Var.new("__arg0")], Call.new(Call.new(Var.new("__arg0"), "block"), "[]")))
     it_parses "foo &.block[0]", Call.new(nil, "foo", block: Block.new([Var.new("__arg0")], Call.new(Call.new(Var.new("__arg0"), "block"), "[]", 0.int32)))
     it_parses "foo &.block=(0)", Call.new(nil, "foo", block: Block.new([Var.new("__arg0")], Call.new(Var.new("__arg0"), "block=", 0.int32)))
     it_parses "foo &.block = 0", Call.new(nil, "foo", block: Block.new([Var.new("__arg0")], Call.new(Var.new("__arg0"), "block=", 0.int32)))
+    it_parses "foo &.block[] = 1", Call.new(nil, "foo", block: Block.new([Var.new("__arg0")], Call.new(Call.new(Var.new("__arg0"), "block"), "[]=", 1.int32)))
     it_parses "foo &.block[0] = 1", Call.new(nil, "foo", block: Block.new([Var.new("__arg0")], Call.new(Call.new(Var.new("__arg0"), "block"), "[]=", 0.int32, 1.int32)))
+    it_parses "foo &.[]", Call.new(nil, "foo", block: Block.new([Var.new("__arg0")], Call.new(Var.new("__arg0"), "[]")))
     it_parses "foo &.[0]", Call.new(nil, "foo", block: Block.new([Var.new("__arg0")], Call.new(Var.new("__arg0"), "[]", 0.int32)))
+    it_parses "foo &.[] = 1", Call.new(nil, "foo", block: Block.new([Var.new("__arg0")], Call.new(Var.new("__arg0"), "[]=", 1.int32)))
     it_parses "foo &.[0] = 1", Call.new(nil, "foo", block: Block.new([Var.new("__arg0")], Call.new(Var.new("__arg0"), "[]=", 0.int32, 1.int32)))
     it_parses "foo(&.is_a?(T))", Call.new(nil, "foo", block: Block.new([Var.new("__arg0")], IsA.new(Var.new("__arg0"), "T".path)))
     it_parses "foo(&.!)", Call.new(nil, "foo", block: Block.new([Var.new("__arg0")], Not.new(Var.new("__arg0"))))
@@ -2226,6 +2236,31 @@ module Crystal
 
     assert_syntax_error "lib Foo%end", %(unexpected token: "%")
 
+    assert_syntax_error "foo.[]? = 1"
+    assert_syntax_error "foo.[]? += 1"
+    assert_syntax_error "foo[0]? = 1"
+    assert_syntax_error "foo[0]? += 1"
+    assert_syntax_error "foo.[0]? = 1"
+    assert_syntax_error "foo.[0]? += 1"
+    assert_syntax_error "foo &.[0]? = 1"
+    assert_syntax_error "foo &.[0]? += 1"
+
+    assert_syntax_error "foo &.[]?=(1)"
+    assert_syntax_error "foo &.[]? = 1"
+    assert_syntax_error "foo &.[]? 0 =(1)"
+    assert_syntax_error "foo &.[]? 0 = 1"
+    assert_syntax_error "foo &.[]?(0)=(1)"
+    assert_syntax_error "foo &.[]?(0) = 1"
+    assert_syntax_error "foo &.[] 0 =(1)"
+    assert_syntax_error "foo &.[] 0 = 1"
+    assert_syntax_error "foo &.[](0)=(1)"
+    assert_syntax_error "foo &.[](0) = 1"
+
+    assert_syntax_error "foo &.bar.[] 0 =(1)"
+    assert_syntax_error "foo &.bar.[] 0 = 1"
+    assert_syntax_error "foo &.bar.[](0)=(1)"
+    assert_syntax_error "foo &.bar.[](0) = 1"
+
     describe "end locations" do
       assert_end_location "nil"
       assert_end_location "false"
@@ -2821,5 +2856,17 @@ module Crystal
       node = Parser.parse(source).as(Annotation).path
       node_source(source, node).should eq("::Foo")
     end
+
+    it "sets args_in_brackets to false for `a.b`" do
+      parser = Parser.new("a.b")
+      node = parser.parse.as(Call)
+      node.args_in_brackets?.should be_false
+    end
+
+    it "sets args_in_brackets to true for `a[b]`" do
+      parser = Parser.new("a[b]")
+      node = parser.parse.as(Call)
+      node.args_in_brackets?.should be_true
+    end
   end
 end
diff --git a/spec/support/syntax.cr b/spec/support/syntax.cr
index e1fd8f43d951..a6fe6286d11b 100644
--- a/spec/support/syntax.cr
+++ b/spec/support/syntax.cr
@@ -133,8 +133,8 @@ class Crystal::ASTNode
   end
 end
 
-def assert_syntax_error(str, message = nil, line = nil, column = nil, metafile = __FILE__, metaline = __LINE__, metaendline = __END_LINE__)
-  it "says syntax error on #{str.inspect}", metafile, metaline, metaendline do
+def assert_syntax_error(str, message = nil, line = nil, column = nil, metafile = __FILE__, metaline = __LINE__, metaendline = __END_LINE__, *, focus : Bool = false)
+  it "says syntax error on #{str.inspect}", metafile, metaline, metaendline, focus: focus do
     begin
       parse str
       fail "Expected SyntaxException to be raised", metafile, metaline
diff --git a/src/compiler/crystal/syntax/ast.cr b/src/compiler/crystal/syntax/ast.cr
index f6d314371034..9ccd8dda1f69 100644
--- a/src/compiler/crystal/syntax/ast.cr
+++ b/src/compiler/crystal/syntax/ast.cr
@@ -653,6 +653,7 @@ module Crystal
     property visibility = Visibility::Public
     property? global : Bool
     property? expansion = false
+    property? args_in_brackets = false
     property? has_parentheses = false
 
     def initialize(@obj, @name, @args = [] of ASTNode, @block = nil, @block_arg = nil, @named_args = nil, @global : Bool = false)
diff --git a/src/compiler/crystal/syntax/parser.cr b/src/compiler/crystal/syntax/parser.cr
index bd7c67a975b8..7153e0ede247 100644
--- a/src/compiler/crystal/syntax/parser.cr
+++ b/src/compiler/crystal/syntax/parser.cr
@@ -735,6 +735,9 @@ module Crystal
 
             case @token.type
             when .op_eq?
+              atomic = Call.new(atomic, name)
+              unexpected_token unless can_be_assigned?(atomic)
+
               # Rewrite 'f.x = arg' as f.x=(arg)
               next_token
 
@@ -760,15 +763,20 @@ module Crystal
                 end_location = arg.end_location
               end
 
-              atomic = Call.new(atomic, "#{name}=", arg).at(location).at_end(end_location)
+              atomic.at(location).at_end(end_location)
+              atomic.name = "#{name}="
+              atomic.args = [arg] of ASTNode
               atomic.name_location = name_location
               next
             when .assignment_operator?
+              call = Call.new(atomic, name)
+              unexpected_token unless can_be_assigned?(call)
+
               op_name_location = @token.location
               method = @token.type.to_s.byte_slice(0, @token.type.to_s.size - 1)
               next_token_skip_space_or_newline
               value = parse_op_assign
-              call = Call.new(atomic, name).at(location)
+              call.at(location)
               call.name_location = name_location
               atomic = OpAssign.new(call, method, value).at(location)
               atomic.name_location = op_name_location
@@ -848,7 +856,8 @@ module Crystal
           atomic = Call.new(atomic, method_name, (args || [] of ASTNode), block, block_arg, named_args).at(location)
           atomic.name_location = name_location
           atomic.end_location = end_location
-          atomic.name_size = 0 if atomic.is_a?(Call)
+          atomic.name_size = 0
+          atomic.args_in_brackets = true
           atomic
         else
           break
@@ -1622,7 +1631,7 @@ module Crystal
       elsif @token.type.op_lsquare?
         call = parse_atomic_method_suffix obj, location
 
-        if @token.type.op_eq? && call.is_a?(Call)
+        if @token.type.op_eq? && call.is_a?(Call) && can_be_assigned?(call)
           next_token_skip_space
           exp = parse_op_assign
           call.name = "#{call.name}="
@@ -1643,6 +1652,8 @@ module Crystal
         call = call.as(Call)
 
         if @token.type.op_eq?
+          unexpected_token unless can_be_assigned?(call)
+
           next_token_skip_space
           if @token.type.op_lparen?
             next_token_skip_space
@@ -1660,7 +1671,7 @@ module Crystal
         else
           call = parse_atomic_method_suffix call, location
 
-          if @token.type.op_eq? && call.is_a?(Call) && call.name == "[]"
+          if @token.type.op_eq? && call.is_a?(Call) && can_be_assigned?(call)
             next_token_skip_space
             exp = parse_op_assign
             call.name = "#{call.name}="
@@ -6185,7 +6196,10 @@ module Crystal
       when Var, InstanceVar, ClassVar, Path, Global, Underscore
         true
       when Call
-        !node.has_parentheses? && ((node.obj.nil? && node.args.empty? && node.block.nil?) || node.name == "[]")
+        return false if node.has_parentheses?
+        no_args = node.args.empty? && node.named_args.nil? && node.block.nil?
+        return true if Lexer.ident?(node.name) && no_args
+        node.name == "[]" && (node.args_in_brackets? || no_args)
       else
         false
       end