Implemented compilation to SSA form

src/core/errors.go

@@ -0,0 +1,27 @@
+package core
+
+import (
+	"fmt"
+
+	"git.urbach.dev/cli/q/src/errors"
+)
+
+var (
+	InvalidExpression = errors.String("Invalid expression")
+	InvalidNumber     = errors.String("Invalid number")
+	InvalidRune       = errors.String("Invalid rune")
+)
+
+// UnknownIdentifier represents unknown identifiers.
+type UnknownIdentifier struct {
+	Name        string
+	CorrectName string
+}
+
+func (err *UnknownIdentifier) Error() string {
+	if err.CorrectName != "" {
+		return fmt.Sprintf("Unknown identifier '%s', did you mean '%s'?", err.Name, err.CorrectName)
+	}
+
+	return fmt.Sprintf("Unknown identifier '%s'", err.Name)
+}