I had printed the shader code, translated code by ANGLE, and error info when compile and link by mesa.
a)  scoping.valid.local_int_variable_hides_struct_type
--original-shader--
#version 100
precision mediump float;
bool isOk (int a, int b) { return (a == b); }
varying float v_in0;
uniform int ref_out0;
int out0;


struct S { int val; };

void main()
{
	int in0 = int(v_in0 * 1.0025);

	int S = S(in0).val;
	out0 = S;
	bool RES = isOk(out0, ref_out0);
gl_FragColor = vec4(RES, RES, RES, 1.0);

}

--translated-shader--
bool webgl_26daf0ef1d00ab6d(in int webgl_2420662cd003acfa, in int webgl_44a9acbe7629930d){
return (webgl_2420662cd003acfa == webgl_44a9acbe7629930d);
}
varying float webgl_c64db3cf02d35b2e;
uniform int webgl_20b06c95b742317e;
int webgl_50c85a6bbb49f119;
struct webgl_bc2ee2bf060ca60{
int webgl_d29633f34eb1c59e;
} ;
void main(){
int webgl_e4819ca83edf6f18 = int((webgl_c64db3cf02d35b2e * 1.0025001));
int webgl_bc2ee2bf060ca60 = webgl_bc2ee2bf060ca60(webgl_e4819ca83edf6f18).webgl_d29633f34eb1c59e;
(webgl_50c85a6bbb49f119 = webgl_bc2ee2bf060ca60);
bool webgl_64928d1969e45ae2 = webgl_26daf0ef1d00ab6d(webgl_50c85a6bbb49f119, webgl_20b06c95b742317e);
(gl_FragColor = vec4(webgl_64928d1969e45ae2, webgl_64928d1969e45ae2, webgl_64928d1969e45ae2, 1.0));
}

--info-log--
0:13(48): error: syntax error, unexpected ')', expecting '('

b) local_struct_variable_hides_struct_type
--original-shader--
#version 100
precision mediump float;
bool isOk (int a, int b) { return (a == b); }
varying float v_in0;
uniform int ref_out0;
int out0;


struct S { int val; };

void main()
{
	int in0 = int(v_in0 * 1.0025);

	S S = S(in0);
	out0 = S.val;
	bool RES = isOk(out0, ref_out0);
gl_FragColor = vec4(RES, RES, RES, 1.0);

}

--translated-shader--
bool webgl_26daf0ef1d00ab6d(in int webgl_2420662cd003acfa, in int webgl_44a9acbe7629930d){
return (webgl_2420662cd003acfa == webgl_44a9acbe7629930d);
}
varying float webgl_c64db3cf02d35b2e;
uniform int webgl_20b06c95b742317e;
int webgl_50c85a6bbb49f119;
struct webgl_bc2ee2bf060ca60{
int webgl_d29633f34eb1c59e;
} ;
void main(){
int webgl_e4819ca83edf6f18 = int((webgl_c64db3cf02d35b2e * 1.0025001));
webgl_bc2ee2bf060ca60 webgl_bc2ee2bf060ca60 = webgl_bc2ee2bf060ca60(webgl_e4819ca83edf6f18);
(webgl_50c85a6bbb49f119 = webgl_bc2ee2bf060ca60.webgl_d29633f34eb1c59e);
bool webgl_64928d1969e45ae2 = webgl_26daf0ef1d00ab6d(webgl_50c85a6bbb49f119, webgl_20b06c95b742317e);
(gl_FragColor = vec4(webgl_64928d1969e45ae2, webgl_64928d1969e45ae2, webgl_64928d1969e45ae2, 1.0));
}

--info-log--
0:13(48): error: syntax error, unexpected DOT_TOK, expecting '('

c) scoping.valid.function_parameter_hides_struct_type
--original-shader--
#version 100
precision mediump float;
bool isOk (int a, int b) { return (a == b); }
varying float v_in0;
uniform int ref_out0;
int out0;


struct S { int x; };

int func (int S) { return S; }

void main()
{
	int in0 = int(v_in0 * 1.0025);

	out0 = func(in0);
	bool RES = isOk(out0, ref_out0);
gl_FragColor = vec4(RES, RES, RES, 1.0);

}

--translated-shader--
bool webgl_26daf0ef1d00ab6d(in int webgl_2420662cd003acfa, in int webgl_44a9acbe7629930d){
return (webgl_2420662cd003acfa == webgl_44a9acbe7629930d);
}
varying float webgl_c64db3cf02d35b2e;
uniform int webgl_20b06c95b742317e;
int webgl_50c85a6bbb49f119;
struct webgl_bc2ee2bf060ca60{
int webgl_4fc82888d13de398;
} ;
int webgl_8e5fc8b7c9b6652c(in int webgl_bc2ee2bf060ca60){
return webgl_bc2ee2bf060ca60;
}
void main(){
int webgl_e4819ca83edf6f18 = int((webgl_c64db3cf02d35b2e * 1.0025001));
(webgl_50c85a6bbb49f119 = webgl_8e5fc8b7c9b6652c(webgl_e4819ca83edf6f18));
bool webgl_64928d1969e45ae2 = webgl_26daf0ef1d00ab6d(webgl_50c85a6bbb49f119, webgl_20b06c95b742317e);
(gl_FragColor = vec4(webgl_64928d1969e45ae2, webgl_64928d1969e45ae2, webgl_64928d1969e45ae2, 1.0));
}

--info-log--
0:11(29): error: syntax error, unexpected ';', expecting '('

See 95184, this bug has been fixed in Mesa 12.0. Should we mark it a duplicate?

All of these tests are now skipped with a message like 

WARNING scoping.valid.function_parameter_hides_struct_type_vertex: Skipping test due to tcuSkipList: scoping.valid.function_parameter_hides_struct_type_vertex
WARNING scoping.valid.function_parameter_hides_struct_type_fragment: Skipping test due to tcuSkipList: scoping.valid.function_parameter_hides_struct_type_fragment

I do not know what that means. Closing as NOTABUG.