Disallow duplicate fun parameter names (#11967)

spec/compiler/parser/parser_spec.cr

@@ -1806,6 +1806,9 @@ module Crystal
     assert_syntax_error "def foo(**x, &x); end", "duplicated def parameter name: x"
     assert_syntax_error "def foo(x, **x); end", "duplicated def parameter name: x"
 
+    assert_syntax_error "fun foo(x : Int32, x : Int64); end", "duplicated fun parameter name: x"
+    assert_syntax_error "lib Foo; fun foo(x : Int32, x : Int64); end", "duplicated fun parameter name: x"
+
     assert_syntax_error "Set {1, 2, 3} of Int32"
     assert_syntax_error "Hash {foo: 1} of Int32 => Int32"
     assert_syntax_error "enum Foo < UInt16; end"

src/big/lib_gmp.cr

@@ -196,8 +196,8 @@ lib LibGMP
   # # Conversion
   fun mpf_get_str = __gmpf_get_str(str : UInt8*, expptr : MpExp*, base : Int, n_digits : LibC::SizeT, op : MPF*) : UInt8*
   fun mpf_get_d = __gmpf_get_d(op : MPF*) : Double
-  fun mpf_set_d = __gmpf_set_d(op : MPF*, op : Double)
-  fun mpf_set = __gmpf_set(op : MPF*, op : MPF*)
+  fun mpf_set_d = __gmpf_set_d(rop : MPF*, op : Double)
+  fun mpf_set = __gmpf_set(rop : MPF*, op : MPF*)
   fun mpf_set_z = __gmpf_set_z(rop : MPF*, op : MPZ*)
   fun mpf_set_q = __gmpf_set_q(rop : MPF*, op : MPQ*)
   fun mpf_get_si = __gmpf_get_si(op : MPF*) : SI

src/compiler/crystal/syntax/parser.cr

@@ -5643,6 +5643,12 @@ module Crystal
               arg_type = parse_bare_proc_type
               skip_space_or_newline
 
+              args.each do |arg|
+                if arg.name == arg_name
+                  raise "duplicated fun parameter name: #{arg_name}", arg_location
+                end
+              end
+
               args << Arg.new(arg_name, nil, arg_type).at(arg_location)
 
               push_var_name arg_name if require_body