shader: Reland: Bug fix: Checking unused variables defined with var

internal/shader/shader.go

@@ -322,8 +322,11 @@ func (cs *compileState) parseDecl(b *block, d ast.Decl) ([]shaderir.Stmt, bool)
 					continue
 				}
 
+				// base must be obtained before adding the variables.
 				base := b.totalLocalVariableNum()
-				b.vars = append(b.vars, vs...)
+				for _, v := range vs {
+					b.addNamedLocalVariable(v.name, v.typ, d.Pos())
+				}
 
 				if len(inits) > 0 {
 					for i := range vs {

internal/shader/testdata/array2.go

@@ -5,6 +5,7 @@ func Foo() [3]vec2 {
 	{
 		var b [2]vec2
 		b = a
+		_ = b
 	}
 	var c [3]vec2
 	return c

internal/shader/testdata/blocks3.go

@@ -15,6 +15,7 @@ func Foo(foo vec2) vec4 {
 			r.y = foo.y
 			var foo vec4
 			r.z = bar.z
+			_ = foo
 		}
 	}
 	return r

shader_test.go

@@ -588,6 +588,26 @@ func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
 `)); err != nil {
 		t.Error(err)
 	}
+
+	if _, err := NewShader([]byte(`package main
+
+func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
+	var a int
+	return vec4(0)
+}
+`)); 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 {
+	var a, b int
+	return vec4(0)
+}
+`)); err == nil {
+		t.Errorf("error must be non-nil but was nil")
+	}
 }
 
 func TestShaderBlankLhs(t *testing.T) {