fix: fix incorrect semantic error logging by refactoring error.scala from frontend

src/main/wacc/frontend/Error.scala

@@ -2,7 +2,6 @@ package wacc
 
 import wacc.ast.Position
 import wacc.types._
-import java.io.PrintStream
 
 /** Error types for semantic errors
   */
@@ -24,71 +23,72 @@ enum Error {
   * @param errorContent
   *   Contents of the file to generate code snippets
   */
-def printError(error: Error)(using errorContent: String, stdout: PrintStream): Unit = {
-  stdout.println("Semantic error:")
-  error match {
-    case Error.DuplicateDeclaration(ident) =>
-      printPosition(ident.pos)
-      stdout.println(s"Duplicate declaration of identifier ${ident.v}")
-      highlight(ident.pos, ident.v.length)
-    case Error.UndeclaredVariable(ident) =>
-      printPosition(ident.pos)
-      stdout.println(s"Undeclared variable ${ident.v}")
-      highlight(ident.pos, ident.v.length)
-    case Error.UndefinedFunction(ident) =>
-      printPosition(ident.pos)
-      stdout.println(s"Undefined function ${ident.v}")
-      highlight(ident.pos, ident.v.length)
-    case Error.FunctionParamsMismatch(id, expected, got, funcType) =>
-      printPosition(id.pos)
-      stdout.println(s"Function expects $expected parameters, got $got")
-      stdout.println(
-        s"(function ${id.v} has type (${funcType.params.mkString(", ")}) -> ${funcType.returnType})"
-      )
-      highlight(id.pos, 1)
-    case Error.TypeMismatch(pos, expected, got, msg) =>
-      printPosition(pos)
-      stdout.println(s"Type mismatch: $msg\nExpected: $expected\nGot: $got")
-      highlight(pos, 1)
-    case Error.SemanticError(pos, msg) =>
-      printPosition(pos)
-      stdout.println(msg)
-      highlight(pos, 1)
-    case wacc.Error.InternalError(pos, msg) =>
-      printPosition(pos)
-      stdout.println(s"Internal error: $msg")
-      highlight(pos, 1)
+def formatError(error: Error)(using errorContent: String): String = {
+  val sb = new StringBuilder()
+  sb.append("Semantic error:\n")
+
+  /** Function to format the position of an error
+    *
+    * @param pos
+    *   Position of the error
+    */
+  def formatPosition(pos: Position): Unit = {
+    sb.append(s"(line ${pos.line}, column ${pos.column}):\n")
   }
 
-}
-
-/** Function to highlight a section of code for an error message
-  *
-  * @param pos
-  *   Position of the error
-  * @param size
-  *   Size(in chars) of section to highlight
-  * @param errorContent
-  *   Contents of the file to generate code snippets
-  */
-def highlight(pos: Position, size: Int)(using errorContent: String, stdout: PrintStream): Unit = {
-  val lines = errorContent.split("\n")
-
-  val preLine = if (pos.line > 1) lines(pos.line - 2) else ""
-  val midLine = lines(pos.line - 1)
-  val postLine = if (pos.line < lines.size) lines(pos.line) else ""
-  val linePointer = " " * (pos.column + 2) + ("^" * (size)) + "\n"
-
-  stdout.println(
-    s"  >$preLine\n  >$midLine\n$linePointer  >$postLine"
-  )
-}
-
-/** Function to print the position of an error
-  *
-  * @param pos
-  *   Position of the error
-  */
-def printPosition(pos: Position)(using stdout: PrintStream): Unit = {
-  stdout.println(s"(line ${pos.line}, column ${pos.column}):")
+  /** Function to highlight a section of code for an error message
+    *
+    * @param pos
+    *   Position of the error
+    * @param size
+    *   Size(in chars) of section to highlight
+    */
+  def formatHighlight(pos: Position, size: Int): Unit = {
+    val lines = errorContent.split("\n")
+    val preLine = if (pos.line > 1) lines(pos.line - 2) else ""
+    val midLine = lines(pos.line - 1)
+    val postLine = if (pos.line < lines.size) lines(pos.line) else ""
+    val linePointer = " " * (pos.column + 2) + ("^" * (size)) + "\n"
+
+    sb.append(
+      s"  >$preLine\n  >$midLine\n$linePointer  >$postLine\netscape"
+    )
+  }
+
+  error match {
+    case Error.DuplicateDeclaration(ident) =>
+      formatPosition(ident.pos)
+      sb.append(s"Duplicate declaration of identifier ${ident.v}")
+      formatHighlight(ident.pos, ident.v.length)
+    case Error.UndeclaredVariable(ident) =>
+      formatPosition(ident.pos)
+      sb.append(s"Undeclared variable ${ident.v}")
+      formatHighlight(ident.pos, ident.v.length)
+    case Error.UndefinedFunction(ident) =>
+      formatPosition(ident.pos)
+      sb.append(s"Undefined function ${ident.v}")
+      formatHighlight(ident.pos, ident.v.length)
+    case Error.FunctionParamsMismatch(id, expected, got, funcType) =>
+      formatPosition(id.pos)
+      sb.append(s"Function expects $expected parameters, got $got")
+      sb.append(
+        s"(function ${id.v} has type (${funcType.params.mkString(", ")}) -> ${funcType.returnType})"
+      )
+      formatHighlight(id.pos, 1)
+    case Error.TypeMismatch(pos, expected, got, msg) =>
+      formatPosition(pos)
+      sb.append(s"Type mismatch: $msg\nExpected: $expected\nGot: $got")
+      formatHighlight(pos, 1)
+    case Error.SemanticError(pos, msg) =>
+      formatPosition(pos)
+      sb.append(msg)
+      formatHighlight(pos, 1)
+    case wacc.Error.InternalError(pos, msg) =>
+      formatPosition(pos)
+      sb.append(s"Internal error: $msg")
+      formatHighlight(pos, 1)
+  }
+
+  sb.toString()
+
 }