From 43df98ea8f491b31b580fd909e92d5fea486599d Mon Sep 17 00:00:00 2001
From: Frederick Yin <fkfd@fkfd.me>
Date: Tue, 30 Aug 2022 15:21:25 +0800
Subject: hackc: print syntax error message

---
 projects/hackc/parser.py | 22 ++++++++++++++--------
 projects/hackc/syntax.py | 31 +++++++++++++++++++++----------
 2 files changed, 35 insertions(+), 18 deletions(-)

(limited to 'projects/hackc')

diff --git a/projects/hackc/parser.py b/projects/hackc/parser.py
index 9a927c6..2c34d1b 100644
--- a/projects/hackc/parser.py
+++ b/projects/hackc/parser.py
@@ -35,6 +35,12 @@ class Parser:
         self._extensions = extensions
         self.tokens = []
 
+        # load source code
+        input_file = open(fp)
+        self.source = input_file.read()
+        self.lines = self.source.splitlines()
+        input_file.close()
+
     def print_tokens(self):
         print("LINE\tCOL\tTYPE\tTOKEN")
         for token in self.tokens:
@@ -42,16 +48,10 @@ class Parser:
         print(f"===== {len(self.tokens)} tokens =====")
 
     def tokenize(self):
-        # read file
-        input_file = open(self._fp)
-        source_code = input_file.read()
-        source_lines = source_code.splitlines()
-        input_file.close()
-
         # tokenize code
         self.tokens = []
         in_multicomment = False  # True when inside /* */
-        for line_no, line in enumerate(source_lines):
+        for line_no, line in enumerate(self.lines):
             pos = 0  # current position in line
             line_width = len(line)
             if in_multicomment:
@@ -94,4 +94,10 @@ class Parser:
                     exit(EXIT_CODE_INVALID_TOKEN)
 
     def parse(self):
-        syntax_tree = Class.from_tokens(self.tokens)
+        try:
+            syntax_tree = Class.from_tokens(self.tokens)
+        except JackSyntaxError as err:
+            print_err(f"{self._fp}:{err.token.line_no + 1}")
+            print_err(self.lines[err.token.line_no])
+            print_err(" " * err.token.column + "^ " + err.message)
+            exit(EXIT_CODE_SYNTAX_ERROR)
diff --git a/projects/hackc/syntax.py b/projects/hackc/syntax.py
index c9be157..a07e69e 100644
--- a/projects/hackc/syntax.py
+++ b/projects/hackc/syntax.py
@@ -41,8 +41,15 @@ class Class:
                 f"Expected `{LEFT_BRACE}`, got `{tokens[2]}` instead", tokens[2]
             )
 
-        variables = Variable.from_tokens(tokens[3:])
-        variables.print_verbose()
+        tokens_consumed = 3
+
+        while True:
+            variables, token_cnt = Variable.from_tokens(tokens[tokens_consumed:])
+            if variables is None:
+                break
+            variables.print_verbose()
+            tokens_consumed += token_cnt
+
         return Class(name, variables, [])
 
 
@@ -53,10 +60,9 @@ class Variable:
         self.names = names
 
     @classmethod
-    def from_tokens(cls, tokens: list):
+    def from_tokens(cls, tokens: list) -> tuple:
         """Construct variable declaration statement.
-
-        You can declare multiple variables of one scope and type on the same line.
+        Return a tuple of a Variable instance and number of tokens consumed.
 
         Format:
         <scope> <type> <one or more names, joined with a comma>;
@@ -66,7 +72,7 @@ class Variable:
         """
         if len(tokens) < 4 or tokens[0] not in SCOPES:
             # not variable declaration
-            return None
+            return (None, 0)
 
         scope = tokens[0]
 
@@ -77,10 +83,12 @@ class Variable:
 
         type = tokens[1]
 
+        tokens_consumed = 2
         names = []  # names of variables
         expecting_identifier = True
 
         for token in tokens[2:]:
+            tokens_consumed += 1
             if token.type == "identifier":
                 if expecting_identifier:
                     names.append(token)
@@ -94,19 +102,22 @@ class Variable:
                     expecting_identifier = True
                 else:
                     raise JackSyntaxError(
-                        f"Expected identifier, got `,` instead", token
+                        f"Expected variable name, got `,` instead", token
                     )
             elif token == ";":
                 if expecting_identifier:
                     raise JackSyntaxError(
-                        f"Expected identifier, got `;` instead", token
+                        f"Expected variable name, got `;` instead", token
                     )
                 break
+            else:
+                expected = "variable name" if expecting_identifier else "`,` or `;`"
+                raise JackSyntaxError(f"Expected {expected}, got `{token}` instead", token)
 
-        return Variable(scope, type, names)
+        return (Variable(scope, type, names), tokens_consumed)
 
     def print_verbose(self):
-        print(f"Declare {len(self.names)} variables:")
+        print(f"Declare {len(self.names)} variable(s):")
         for name in self.names:
             print(self.scope, self.type, name)
 
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