internal/shader: Bug fix: Error on duplicated const/var names

Updates #1192

internal/shader/shader.go

@@ -540,6 +540,12 @@ func (s *compileState) parseVariable(block *block, vs *ast.ValueSpec) ([]variabl
 				return nil, nil, nil, false
 			}
 		}
+		for _, c := range block.consts {
+			if c.name == name {
+				s.addError(vs.Pos(), fmt.Sprintf("duplicated local constant/variable name: %s", name))
+				return nil, nil, nil, false
+			}
+		}
 		vars = append(vars, variable{
 			name: name,
 			typ:  t,
@@ -561,12 +567,26 @@ func (s *compileState) parseConstant(block *block, vs *ast.ValueSpec) ([]constan
 
 	var cs []constant
 	for i, n := range vs.Names {
+		name := n.Name
+		for _, c := range block.consts {
+			if c.name == name {
+				s.addError(vs.Pos(), fmt.Sprintf("duplicated local constant name: %s", name))
+				return nil, false
+			}
+		}
+		for _, v := range block.vars {
+			if v.name == name {
+				s.addError(vs.Pos(), fmt.Sprintf("duplicated local constant/variable name: %s", name))
+				return nil, false
+			}
+		}
+
 		es, _, ss, ok := s.parseExpr(block, vs.Values[i], false)
 		if !ok {
 			return nil, false
 		}
 		if len(ss) > 0 {
-			s.addError(vs.Pos(), fmt.Sprintf("invalid constant expression: %s", n))
+			s.addError(vs.Pos(), fmt.Sprintf("invalid constant expression: %s", name))
 			return nil, false
 		}
 		if len(es) != 1 {
@@ -578,7 +598,7 @@ func (s *compileState) parseConstant(block *block, vs *ast.ValueSpec) ([]constan
 			return nil, false
 		}
 		cs = append(cs, constant{
-			name:  n.Name,
+			name:  name,
 			typ:   t,
 			value: es[0].Const,
 		})

shader_test.go

@@ -780,6 +780,65 @@ func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
 	}
 }
 
+func TestShaderDuplicatedVarsAndConstants(t *testing.T) {
+	if _, err := NewShader([]byte(`package main
+
+func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
+	var a = 0
+	const a = 0
+	return vec4(a)
+}
+`)); err == nil {
+		t.Errorf("error must be non-nil but was nil")
+	}
+
+	if _, err := NewShader([]byte(`package main
+
+func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
+	const a = 0
+	var a = 0
+	return vec4(a)
+}
+`)); err == nil {
+		t.Errorf("error must be non-nil but was nil")
+	}
+
+	if _, err := NewShader([]byte(`package main
+
+func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
+	const a = 0
+	const a = 0
+	return vec4(a)
+}
+`)); err == nil {
+		t.Errorf("error must be non-nil but was nil")
+	}
+
+	if _, err := NewShader([]byte(`package main
+
+const U0 = 0
+var U0 float
+
+func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
+	return vec4(a)
+}
+`)); err == nil {
+		t.Errorf("error must be non-nil but was nil")
+	}
+
+	if _, err := NewShader([]byte(`package main
+
+var U0 float
+const U0 = 0
+
+func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
+	return vec4(a)
+}
+`)); err == nil {
+		t.Errorf("error must be non-nil but was nil")
+	}
+}
+
 func TestShaderMatrix(t *testing.T) {
 	const w, h = 16, 16