Add some dash-insensitivity specs for meta functions (#1452)

See sass/sass#792

Author: nex3

spec/core_functions/meta/function_exists.hrx

@@ -35,6 +35,30 @@ a {
   b: true;
 }
 
+<===>
+================================================================================
+<===> same_module/dash_insensitive/dash_to_underscore/input.scss
+@function a_b() {@return null}
+
+c {d: function-exists(a-b)}
+
+<===> same_module/dash_insensitive/dash_to_underscore/output.css
+c {
+  d: true;
+}
+
+<===>
+================================================================================
+<===> same_module/dash_insensitive/underscore_to_dash/input.scss
+@function a-b() {@return null}
+
+c {d: function-exists(a_b)}
+
+<===> same_module/dash_insensitive/underscore_to_dash/output.css
+c {
+  d: true;
+}
+
 <===>
 ================================================================================
 <===> same_module/non_existent/input.scss

spec/core_functions/meta/get_function/same_module.hrx

@@ -69,3 +69,27 @@ a {
   sass-fn: #ff9999;
   css-fn: lighten(red, 30%);
 }
+
+<===>
+================================================================================
+<===> dash_insensitive/dash_to_underscore/input.scss
+@function add_two($v) {@return $v + 2}
+
+a {b: call(get-function(add-two), 10)}
+
+<===> dash_insensitive/dash_to_underscore/output.css
+a {
+  b: 12;
+}
+
+<===>
+================================================================================
+<===> dash_insensitive/underscore_to_dash/input.scss
+@function add-two($v) {@return $v + 2}
+
+a {b: call(get-function(add_two), 10)}
+
+<===> dash_insensitive/underscore_to_dash/output.css
+a {
+  b: 12;
+}

spec/core_functions/meta/global_variable_exists.hrx

@@ -35,6 +35,30 @@ a {
   b: true;
 }
 
+<===>
+================================================================================
+<===> dash_insensitive/dash_to_underscore/input.scss
+$a_b: null;
+
+c {d: global-variable-exists(a-b)}
+
+<===> dash_insensitive/dash_to_underscore/output.css
+c {
+  d: true;
+}
+
+<===>
+================================================================================
+<===> dash_insensitive/underscore_to_dash/input.scss
+$a-b: null;
+
+c {d: global-variable-exists(a_b)}
+
+<===> dash_insensitive/underscore_to_dash/output.css
+c {
+  d: true;
+}
+
 <===>
 ================================================================================
 <===> same_module/non_existent/input.scss

spec/core_functions/meta/variable_exists.hrx

@@ -21,6 +21,30 @@ a {
   b: true;
 }
 
+<===>
+================================================================================
+<===> dash_insensitive/dash_to_underscore/input.scss
+$a_b: null;
+
+c {d: variable-exists(a-b)}
+
+<===> dash_insensitive/dash_to_underscore/output.css
+c {
+  d: true;
+}
+
+<===>
+================================================================================
+<===> dash_insensitive/underscore_to_dash/input.scss
+$a-b: null;
+
+c {d: variable-exists(a_b)}
+
+<===> dash_insensitive/underscore_to_dash/output.css
+c {
+  d: true;
+}
+
 <===>
 ================================================================================
 <===> through_import/input.scss