diff --git a/src/fun/parser.rs b/src/fun/parser.rs
index 747f0219..95935098 100644
--- a/src/fun/parser.rs
+++ b/src/fun/parser.rs
@@ -62,8 +62,10 @@ impl<'a> TermParser<'a> {
   pub fn parse_book(&mut self, default_book: Book, builtin: bool) -> ParseResult<Book> {
     let mut book = default_book;
     let mut indent = self.advance_newlines();
+    let mut last_rule = None;
     while !self.is_eof() {
       let ini_idx = *self.index();
+
       // Imp type definition
       if self.try_parse_keyword("type") {
         let mut prs = PyParser { input: self.input, index: *self.index() };
@@ -72,6 +74,7 @@ impl<'a> TermParser<'a> {
         let end_idx = *self.index();
         prs.add_type(enum_, &mut book, ini_idx, end_idx, builtin)?;
         indent = nxt_indent;
+        last_rule = None;
         continue;
       }
       // Imp record type definition
@@ -82,8 +85,10 @@ impl<'a> TermParser<'a> {
         let end_idx = *self.index();
         prs.add_object(obj, &mut book, ini_idx, end_idx, builtin)?;
         indent = nxt_indent;
+        last_rule = None;
         continue;
       }
+
       // Imp function definition
       if self.try_parse_keyword("def") {
         let mut prs = PyParser { input: self.input, index: *self.index() };
@@ -92,20 +97,46 @@ impl<'a> TermParser<'a> {
         let end_idx = *self.index();
         prs.add_def(def, &mut book, ini_idx, end_idx)?;
         indent = nxt_indent;
+        last_rule = None;
         continue;
       }
+
       // Fun type definition
       if self.try_parse_keyword("data") {
         let (nam, adt) = self.parse_datatype(builtin)?;
         let end_idx = *self.index();
         self.with_ctx(book.add_adt(nam, adt), ini_idx, end_idx)?;
         indent = self.advance_newlines();
+        last_rule = None;
         continue;
       }
+
       // Fun function definition
+      let ini_idx = *self.index();
       let (name, rule) = self.parse_rule()?;
-      book.add_rule(name, rule, builtin);
+      let end_idx = *self.index();
+      // Add to book
+      if let Some(def) = book.defs.get_mut(&name) {
+        if let Some(last_rule) = last_rule {
+          if last_rule == name {
+            // Continuing with a new rule to the current definition
+            def.rules.push(rule);
+          } else {
+            // Trying to add a new rule to a previous definition, coming from a different rule.
+            let msg = format!("Redefinition of function '{name}'");
+            return self.with_ctx(Err(msg), ini_idx, end_idx);
+          }
+        } else {
+          // Trying to add a new rule to a previous definition, coming from another kind of top-level.
+          let msg = format!("Redefinition of function '{name}'");
+          return self.with_ctx(Err(msg), ini_idx, end_idx);
+        }
+      } else {
+        // Adding the first rule of a new definition
+        book.defs.insert(name.clone(), Definition { name: name.clone(), rules: vec![rule], builtin });
+      }
       indent = self.advance_newlines();
+      last_rule = Some(name);
     }
 
     Ok(book)
@@ -756,14 +787,6 @@ impl Book {
     }
     Ok(())
   }
-
-  fn add_rule(&mut self, name: Name, rule: Rule, builtin: bool) {
-    if let Some(def) = self.defs.get_mut(&name) {
-      def.rules.push(rule);
-    } else {
-      self.defs.insert(name.clone(), Definition { name, rules: vec![rule], builtin });
-    }
-  }
 }
 
 impl<'a> ParserCommons<'a> for TermParser<'a> {}
@@ -789,13 +812,8 @@ pub trait ParserCommons<'a>: Parser<'a> {
   }
 
   fn parse_bend_name(&mut self) -> ParseResult<Name> {
-    let nam = self.parse_exactly_name()?;
-    Ok(Name::new(nam))
-  }
-
-  fn parse_exactly_name(&mut self) -> ParseResult<String> {
     let name = self.take_while(|c| c.is_ascii_alphanumeric() || c == '_' || c == '.' || c == '-' || c == '/');
-    if name.is_empty() { self.expected("name") } else { Ok(name.to_owned()) }
+    if name.is_empty() { self.expected("name") } else { Ok(Name::new(name.to_owned())) }
   }
 
   /// Consumes exactly the text without skipping.
@@ -862,14 +880,6 @@ pub trait ParserCommons<'a>: Parser<'a> {
     self.advance_trivia_inline();
   }
 
-  fn skip_trivia_maybe_inline(&mut self, inline: bool) {
-    if inline {
-      self.skip_trivia_inline();
-    } else {
-      self.skip_trivia();
-    }
-  }
-
   fn expected_spanned<T>(&mut self, exp: &str, ini_idx: usize, end_idx: usize) -> ParseResult<T> {
     let is_eof = self.is_eof();
     let detected = DisplayFn(|f| if is_eof { write!(f, " end of input") } else { Ok(()) });
diff --git a/src/imp/parser.rs b/src/imp/parser.rs
index 2c1e1a9c..dfffbb14 100644
--- a/src/imp/parser.rs
+++ b/src/imp/parser.rs
@@ -90,7 +90,11 @@ impl<'a> PyParser<'a> {
   /// <var> <postfix>?
   ///
   fn parse_simple_expr(&mut self, inline: bool) -> ParseResult<Expr> {
-    self.skip_trivia_maybe_inline(inline);
+    if inline {
+      self.skip_trivia_inline();
+    } else {
+      self.skip_trivia();
+    }
     let Some(head) = self.peek_one() else { return self.expected("expression")? };
 
     let ini_idx = *self.index();
@@ -133,7 +137,7 @@ impl<'a> PyParser<'a> {
         }
       }
       // List or Comprehension
-      '[' => self.list_or_comprehension()?,
+      '[' => self.parse_list_or_comprehension()?,
       // Symbol
       '`' => Expr::Num { val: Num::U24(self.parse_quoted_symbol()?) },
       // String
@@ -173,7 +177,11 @@ impl<'a> PyParser<'a> {
     let end_idx = *self.index();
 
     // postfixes
-    self.skip_trivia_maybe_inline(inline);
+    if inline {
+      self.skip_trivia_inline();
+    } else {
+      self.skip_trivia();
+    }
     // call
     if self.starts_with("(") {
       self.advance_one();
@@ -265,7 +273,7 @@ impl<'a> PyParser<'a> {
     Ok((key, val))
   }
 
-  fn list_or_comprehension(&mut self) -> ParseResult<Expr> {
+  fn parse_list_or_comprehension(&mut self) -> ParseResult<Expr> {
     self.consume_exactly("[")?;
 
     // Empty list
@@ -316,7 +324,11 @@ impl<'a> PyParser<'a> {
       }
     }
 
-    self.skip_trivia_maybe_inline(inline);
+    if inline {
+      self.skip_trivia_inline();
+    } else {
+      self.skip_trivia();
+    }
 
     // lambda
     if self.try_parse_keyword("lambda") | self.try_consume_exactly("λ") {
@@ -350,18 +362,26 @@ impl<'a> PyParser<'a> {
   /// <simple> (<infix_op> <infix>)?
   fn parse_infix_expr(&mut self, prec: usize, inline: bool) -> ParseResult<Expr> {
     maybe_grow(|| {
-      self.skip_trivia_maybe_inline(inline);
+      if inline {
+        self.skip_trivia_inline();
+      } else {
+        self.skip_trivia();
+      }
       if prec > PREC.len() - 1 {
         return self.parse_simple_expr(inline);
       }
       let mut lhs = self.parse_infix_expr(prec + 1, inline)?;
-      self.skip_trivia_maybe_inline(inline);
+      if inline {
+        self.skip_trivia_inline();
+      } else {
+        self.skip_trivia();
+      }
       while let Some(op) = self.peek_oper() {
         if PREC[prec].iter().any(|r| *r == op) {
           self.parse_oper()?;
           let rhs = self.parse_infix_expr(prec + 1, inline)?;
           lhs = Expr::Bin { op, lhs: Box::new(lhs), rhs: Box::new(rhs) };
-          self.advance_trivia_inline();
+          self.skip_trivia_inline();
         } else {
           break;
         }
@@ -423,7 +443,7 @@ impl<'a> PyParser<'a> {
     let ini_idx = *self.index();
     let pat = self.parse_assign_pattern()?;
     let end_idx = *self.index();
-    self.advance_trivia_inline();
+    self.skip_trivia_inline();
 
     // Assignment
     if self.starts_with("=") {
@@ -472,7 +492,7 @@ impl<'a> PyParser<'a> {
   }
 
   fn parse_in_place_op(&mut self) -> ParseResult<Option<InPlaceOp>> {
-    self.advance_trivia_inline();
+    self.skip_trivia_inline();
     let op = if self.starts_with("+=") {
       self.consume("+=")?;
       Some(InPlaceOp::Add)
@@ -579,7 +599,7 @@ impl<'a> PyParser<'a> {
     let arg = self.parse_expr(true)?;
     let end_idx = *self.index();
 
-    self.advance_trivia_inline();
+    self.skip_trivia_inline();
     match (arg, self.starts_with("=")) {
       (Expr::Var { nam }, true) => {
         self.advance_one();
@@ -591,24 +611,15 @@ impl<'a> PyParser<'a> {
     }
   }
 
-  fn name_or_wildcard(&mut self) -> ParseResult<Option<Name>> {
-    self.labelled(
-      |p| {
-        if p.try_consume_exactly("_") {
-          Ok(None)
-        } else {
-          let nam = p.parse_bend_name()?;
-          Ok(Some(nam))
-        }
-      },
-      "name or '_'",
-    )
-  }
-
   fn parse_match_case(&mut self, indent: &mut Indent) -> ParseResult<(MatchArm, Indent)> {
     self.parse_keyword("case")?;
     self.skip_trivia_inline();
-    let pat = self.name_or_wildcard()?;
+    let pat = if self.try_consume_exactly("_") {
+      None
+    } else {
+      let nam = self.labelled(|p| p.parse_bend_name(), "name or '_'")?;
+      Some(nam)
+    };
     self.skip_trivia_inline();
     self.consume_exactly(":")?;
     self.consume_new_line()?;
@@ -683,7 +694,7 @@ impl<'a> PyParser<'a> {
       return self.expected("number or '_'")?;
     };
 
-    self.advance_trivia_inline();
+    self.skip_trivia_inline();
     self.consume_exactly(":")?;
     self.consume_new_line()?;
     indent.enter_level();
@@ -853,7 +864,7 @@ impl<'a> PyParser<'a> {
     // Chn pattern
     if self.starts_with("$") {
       self.advance_one();
-      self.advance_trivia_inline();
+      self.skip_trivia_inline();
       let nam = self.parse_bend_name()?;
       return Ok(AssignPattern::Chn(nam));
     }
diff --git a/tests/golden_tests/parse_file/redefinition_fun_imp.bend b/tests/golden_tests/parse_file/redefinition_fun_imp.bend
new file mode 100644
index 00000000..a9790a2c
--- /dev/null
+++ b/tests/golden_tests/parse_file/redefinition_fun_imp.bend
@@ -0,0 +1,4 @@
+# We shouldn't allow a fun rule to be extended by an imp function
+(A) = @x x
+def A:
+  return 0
\ No newline at end of file
diff --git a/tests/golden_tests/parse_file/redefinition_imp_fun.bend b/tests/golden_tests/parse_file/redefinition_imp_fun.bend
new file mode 100644
index 00000000..1e28f3c8
--- /dev/null
+++ b/tests/golden_tests/parse_file/redefinition_imp_fun.bend
@@ -0,0 +1,5 @@
+# We shouldn't allow an imp function to have a fun rule
+def A:
+  return 0
+
+(A) = 1
\ No newline at end of file
diff --git a/tests/golden_tests/parse_file/redefinition_with_def_between.bend b/tests/golden_tests/parse_file/redefinition_with_def_between.bend
new file mode 100644
index 00000000..b0215744
--- /dev/null
+++ b/tests/golden_tests/parse_file/redefinition_with_def_between.bend
@@ -0,0 +1,4 @@
+# We shouldn't allow rules of other functions in the middle of a definition
+(A) = @x x
+(B) = @x x
+(A) = @x x
\ No newline at end of file
diff --git a/tests/golden_tests/parse_file/redefinition_with_object_between.bend b/tests/golden_tests/parse_file/redefinition_with_object_between.bend
new file mode 100644
index 00000000..37150485
--- /dev/null
+++ b/tests/golden_tests/parse_file/redefinition_with_object_between.bend
@@ -0,0 +1,3 @@
+A = 0
+object B
+A = 1
\ No newline at end of file
diff --git a/tests/golden_tests/parse_file/redefinition_with_type_between.bend b/tests/golden_tests/parse_file/redefinition_with_type_between.bend
new file mode 100644
index 00000000..5a32ccae
--- /dev/null
+++ b/tests/golden_tests/parse_file/redefinition_with_type_between.bend
@@ -0,0 +1,3 @@
+A = 0
+data B = B
+A = 1
\ No newline at end of file
diff --git a/tests/snapshots/parse_file__redefinition_fun_imp.bend.snap b/tests/snapshots/parse_file__redefinition_fun_imp.bend.snap
new file mode 100644
index 00000000..01b3a8b5
--- /dev/null
+++ b/tests/snapshots/parse_file__redefinition_fun_imp.bend.snap
@@ -0,0 +1,9 @@
+---
+source: tests/golden_tests.rs
+input_file: tests/golden_tests/parse_file/redefinition_fun_imp.bend
+---
+Errors:
+In tests/golden_tests/parse_file/redefinition_fun_imp.bend :
+Redefinition of function 'A'.
+  3 | def A:
+  4 |   return 0
diff --git a/tests/snapshots/parse_file__redefinition_imp_fun.bend.snap b/tests/snapshots/parse_file__redefinition_imp_fun.bend.snap
new file mode 100644
index 00000000..e14ae79d
--- /dev/null
+++ b/tests/snapshots/parse_file__redefinition_imp_fun.bend.snap
@@ -0,0 +1,8 @@
+---
+source: tests/golden_tests.rs
+input_file: tests/golden_tests/parse_file/redefinition_imp_fun.bend
+---
+Errors:
+In tests/golden_tests/parse_file/redefinition_imp_fun.bend :
+Redefinition of function 'A'
+  5 | (A) = 1
diff --git a/tests/snapshots/parse_file__redefinition_with_def_between.bend.snap b/tests/snapshots/parse_file__redefinition_with_def_between.bend.snap
new file mode 100644
index 00000000..aca21a52
--- /dev/null
+++ b/tests/snapshots/parse_file__redefinition_with_def_between.bend.snap
@@ -0,0 +1,8 @@
+---
+source: tests/golden_tests.rs
+input_file: tests/golden_tests/parse_file/redefinition_with_def_between.bend
+---
+Errors:
+In tests/golden_tests/parse_file/redefinition_with_def_between.bend :
+Redefinition of function 'A'
+   4 | (A) = @x x
diff --git a/tests/snapshots/parse_file__redefinition_with_object_between.bend.snap b/tests/snapshots/parse_file__redefinition_with_object_between.bend.snap
new file mode 100644
index 00000000..a95e8146
--- /dev/null
+++ b/tests/snapshots/parse_file__redefinition_with_object_between.bend.snap
@@ -0,0 +1,8 @@
+---
+source: tests/golden_tests.rs
+input_file: tests/golden_tests/parse_file/redefinition_with_object_between.bend
+---
+Errors:
+In tests/golden_tests/parse_file/redefinition_with_object_between.bend :
+Redefinition of function 'A'
+  3 | A = 1
diff --git a/tests/snapshots/parse_file__redefinition_with_type_between.bend.snap b/tests/snapshots/parse_file__redefinition_with_type_between.bend.snap
new file mode 100644
index 00000000..264ad129
--- /dev/null
+++ b/tests/snapshots/parse_file__redefinition_with_type_between.bend.snap
@@ -0,0 +1,8 @@
+---
+source: tests/golden_tests.rs
+input_file: tests/golden_tests/parse_file/redefinition_with_type_between.bend
+---
+Errors:
+In tests/golden_tests/parse_file/redefinition_with_type_between.bend :
+Redefinition of function 'A'
+  3 | A = 1