diff --git a/src/ast/operations.rs b/src/ast/operations.rs
index 045bad7852..90ea91f7c5 100644
--- a/src/ast/operations.rs
+++ b/src/ast/operations.rs
@@ -1,3 +1,4 @@
+use once_cell::unsync::OnceCell;
 use rustpython_parser::ast::{Constant, Expr, ExprKind, Location, Stmt, StmtKind};
 
 use crate::ast::types::{BindingKind, Range, Scope};
@@ -120,15 +121,15 @@ pub fn is_unpacking_assignment(stmt: &Stmt) -> bool {
 
 /// Struct used to efficiently slice source code at (row, column) Locations.
 pub struct SourceCodeLocator<'a> {
-    content: &'a str,
-    offsets: Vec<Vec<usize>>,
+    contents: &'a str,
+    offsets: OnceCell<Vec<Vec<usize>>>,
 }
 
 impl<'a> SourceCodeLocator<'a> {
-    pub fn new(content: &'a str) -> Self {
+    pub fn new(contents: &'a str) -> Self {
         SourceCodeLocator {
-            content,
-            offsets: Self::compute_offsets(content),
+            contents,
+            offsets: OnceCell::new(),
         }
     }
 
@@ -145,15 +146,22 @@ impl<'a> SourceCodeLocator<'a> {
         offsets
     }
 
+    fn get_or_init_offsets(&self) -> &Vec<Vec<usize>> {
+        self.offsets
+            .get_or_init(|| Self::compute_offsets(self.contents))
+    }
+
     pub fn slice_source_code_at(&self, location: &Location) -> &'a str {
-        let offset = self.offsets[location.row() - 1][location.column() - 1];
-        &self.content[offset..]
+        let offsets = self.get_or_init_offsets();
+        let offset = offsets[location.row() - 1][location.column() - 1];
+        &self.contents[offset..]
     }
 
     pub fn slice_source_code_range(&self, range: &Range) -> &'a str {
-        let start = self.offsets[range.location.row() - 1][range.location.column() - 1];
-        let end = self.offsets[range.end_location.row() - 1][range.end_location.column() - 1];
-        &self.content[start..end]
+        let offsets = self.get_or_init_offsets();
+        let start = offsets[range.location.row() - 1][range.location.column() - 1];
+        let end = offsets[range.end_location.row() - 1][range.end_location.column() - 1];
+        &self.contents[start..end]
     }
 
     pub fn partition_source_code_at(
@@ -161,14 +169,15 @@ impl<'a> SourceCodeLocator<'a> {
         outer: &Range,
         inner: &Range,
     ) -> (&'a str, &'a str, &'a str) {
-        let outer_start = self.offsets[outer.location.row() - 1][outer.location.column() - 1];
-        let outer_end = self.offsets[outer.end_location.row() - 1][outer.end_location.column() - 1];
-        let inner_start = self.offsets[inner.location.row() - 1][inner.location.column() - 1];
-        let inner_end = self.offsets[inner.end_location.row() - 1][inner.end_location.column() - 1];
+        let offsets = self.get_or_init_offsets();
+        let outer_start = offsets[outer.location.row() - 1][outer.location.column() - 1];
+        let outer_end = offsets[outer.end_location.row() - 1][outer.end_location.column() - 1];
+        let inner_start = offsets[inner.location.row() - 1][inner.location.column() - 1];
+        let inner_end = offsets[inner.end_location.row() - 1][inner.end_location.column() - 1];
         (
-            &self.content[outer_start..inner_start],
-            &self.content[inner_start..inner_end],
-            &self.content[inner_end..outer_end],
+            &self.contents[outer_start..inner_start],
+            &self.contents[inner_start..inner_end],
+            &self.contents[inner_end..outer_end],
         )
     }
 }
@@ -181,20 +190,19 @@ mod tests {
     fn source_code_locator_init() {
         let content = "x = 1\ny = 2\nz = x + y\n";
         let locator = SourceCodeLocator::new(content);
-        assert_eq!(locator.offsets.len(), 4);
-        assert_eq!(locator.offsets[0], [0, 1, 2, 3, 4, 5]);
-        assert_eq!(locator.offsets[1], [6, 7, 8, 9, 10, 11]);
-        assert_eq!(locator.offsets[2], [12, 13, 14, 15, 16, 17, 18, 19, 20, 21]);
-        assert!(locator.offsets[3].is_empty());
+        let offsets = locator.get_or_init_offsets();
+        assert_eq!(offsets.len(), 4);
+        assert_eq!(offsets[0], [0, 1, 2, 3, 4, 5]);
+        assert_eq!(offsets[1], [6, 7, 8, 9, 10, 11]);
+        assert_eq!(offsets[2], [12, 13, 14, 15, 16, 17, 18, 19, 20, 21]);
+        assert!(offsets[3].is_empty());
 
         let content = "# \u{4e9c}\nclass Foo:\n    \"\"\".\"\"\"";
         let locator = SourceCodeLocator::new(content);
-        assert_eq!(locator.offsets.len(), 3);
-        assert_eq!(locator.offsets[0], [0, 1, 2, 5]);
-        assert_eq!(locator.offsets[1], [6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16]);
-        assert_eq!(
-            locator.offsets[2],
-            [17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27]
-        );
+        let offsets = locator.get_or_init_offsets();
+        assert_eq!(offsets.len(), 3);
+        assert_eq!(offsets[0], [0, 1, 2, 5]);
+        assert_eq!(offsets[1], [6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16]);
+        assert_eq!(offsets[2], [17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27]);
     }
 }
diff --git a/src/check_ast.rs b/src/check_ast.rs
index 756df1b1a6..bebdf95cb3 100644
--- a/src/check_ast.rs
+++ b/src/check_ast.rs
@@ -5,7 +5,6 @@ use std::ops::Deref;
 use std::path::Path;
 
 use log::error;
-use once_cell::unsync::OnceCell;
 use rustpython_parser::ast::{
     Arg, Arguments, Constant, Excepthandler, ExcepthandlerKind, Expr, ExprContext, ExprKind,
     KeywordData, Operator, Stmt, StmtKind, Suite,
@@ -39,13 +38,11 @@ pub const GLOBAL_SCOPE_INDEX: usize = 0;
 pub struct Checker<'a> {
     // Input data.
     path: &'a Path,
-    content: &'a str,
     autofix: &'a fixer::Mode,
     pub(crate) settings: &'a Settings,
+    pub(crate) locator: &'a SourceCodeLocator<'a>,
     // Computed checks.
     checks: Vec<Check>,
-    // Efficient source-code slicing.
-    locator: OnceCell<SourceCodeLocator<'a>>,
     // Docstring tracking.
     docstrings: Vec<(Definition<'a>, Visibility)>,
     // Edit tracking.
@@ -79,14 +76,13 @@ impl<'a> Checker<'a> {
         settings: &'a Settings,
         autofix: &'a fixer::Mode,
         path: &'a Path,
-        content: &'a str,
+        locator: &'a SourceCodeLocator,
     ) -> Checker<'a> {
         Checker {
             settings,
             autofix,
             path,
-            content,
-            locator: OnceCell::new(),
+            locator,
             checks: Default::default(),
             docstrings: Default::default(),
             deletions: Default::default(),
@@ -114,12 +110,6 @@ impl<'a> Checker<'a> {
         }
     }
 
-    /// Get access to a lazily-initialized `SourceCodeLocator` for the file contents.
-    pub fn get_locator(&self) -> &SourceCodeLocator {
-        self.locator
-            .get_or_init(|| SourceCodeLocator::new(self.content))
-    }
-
     /// Return `true` if a patch should be generated under the given autofix `Mode`.
     pub fn patch(&self) -> bool {
         self.autofix.patch()
@@ -2146,7 +2136,7 @@ impl<'a> Checker<'a> {
                             ImportKind::ImportFrom => pyflakes::fixes::remove_unused_import_froms,
                         };
 
-                        match removal_fn(self.get_locator(), &full_names, child, parent, &deleted) {
+                        match removal_fn(self.locator, &full_names, child, parent, &deleted) {
                             Ok(fix) => Some(fix),
                             Err(e) => {
                                 error!("Failed to fix unused imports: {}", e);
@@ -2306,12 +2296,12 @@ impl<'a> Checker<'a> {
 
 pub fn check_ast(
     python_ast: &Suite,
-    contents: &str,
+    locator: &SourceCodeLocator,
     settings: &Settings,
     autofix: &fixer::Mode,
     path: &Path,
 ) -> Vec<Check> {
-    let mut checker = Checker::new(settings, autofix, path, contents);
+    let mut checker = Checker::new(settings, autofix, path, locator);
     checker.push_scope(Scope::new(ScopeKind::Module));
     checker.bind_builtins();
 
diff --git a/src/check_tokens.rs b/src/check_tokens.rs
index fd29e04456..7c37098186 100644
--- a/src/check_tokens.rs
+++ b/src/check_tokens.rs
@@ -9,7 +9,7 @@ use crate::{flake8_quotes, pycodestyle, Settings};
 
 pub fn check_tokens(
     checks: &mut Vec<Check>,
-    contents: &str,
+    locator: &SourceCodeLocator,
     tokens: &[LexResult],
     settings: &Settings,
 ) {
@@ -19,16 +19,13 @@ pub fn check_tokens(
         | settings.enabled.contains(&CheckCode::Q002)
         | settings.enabled.contains(&CheckCode::Q003);
 
-    // TODO(charlie): Use a shared SourceCodeLocator between this site and the AST traversal.
-    let locator = SourceCodeLocator::new(contents);
-
     let mut state_machine = StateMachine::new();
     for (start, tok, end) in tokens.iter().flatten() {
         // W605
         if enforce_invalid_escape_sequence {
             if matches!(tok, Tok::String { .. }) {
                 checks.extend(pycodestyle::checks::invalid_escape_sequence(
-                    &locator, start, end,
+                    locator, start, end,
                 ));
             }
         }
@@ -38,7 +35,7 @@ pub fn check_tokens(
             let is_docstring = state_machine.consume(tok);
             if matches!(tok, Tok::String { .. }) {
                 if let Some(check) = flake8_quotes::checks::quotes(
-                    &locator,
+                    locator,
                     start,
                     end,
                     is_docstring,
diff --git a/src/docstrings/helpers.rs b/src/docstrings/helpers.rs
index 29b0758530..ebdf23f9d8 100644
--- a/src/docstrings/helpers.rs
+++ b/src/docstrings/helpers.rs
@@ -27,7 +27,7 @@ pub fn leading_space(line: &str) -> String {
 /// Extract the leading indentation from a docstring.
 pub fn indentation<'a>(checker: &'a Checker, docstring: &Expr) -> &'a str {
     let range = Range::from_located(docstring);
-    checker.get_locator().slice_source_code_range(&Range {
+    checker.locator.slice_source_code_range(&Range {
         location: Location::new(range.location.row(), 1),
         end_location: Location::new(range.location.row(), range.location.column()),
     })
diff --git a/src/linter.rs b/src/linter.rs
index f601189092..ee3983a0f3 100644
--- a/src/linter.rs
+++ b/src/linter.rs
@@ -9,6 +9,7 @@ use log::debug;
 use rustpython_parser::lexer::LexResult;
 use rustpython_parser::{lexer, parser};
 
+use crate::ast::operations::SourceCodeLocator;
 use crate::ast::types::Range;
 use crate::autofix::fixer;
 use crate::autofix::fixer::fix_file;
@@ -46,13 +47,16 @@ pub(crate) fn check_path(
     // Aggregate all checks.
     let mut checks: Vec<Check> = vec![];
 
+    // Initialize the SourceCodeLocator (which computes offsets lazily).
+    let locator = SourceCodeLocator::new(contents);
+
     // Run the token-based checks.
     if settings
         .enabled
         .iter()
         .any(|check_code| matches!(check_code.lint_source(), LintSource::Tokens))
     {
-        check_tokens(&mut checks, contents, &tokens, settings);
+        check_tokens(&mut checks, &locator, &tokens, settings);
     }
 
     // Run the AST-based checks.
@@ -63,7 +67,7 @@ pub(crate) fn check_path(
     {
         match parser::parse_program_tokens(tokens, "<filename>") {
             Ok(python_ast) => {
-                checks.extend(check_ast(&python_ast, contents, settings, autofix, path))
+                checks.extend(check_ast(&python_ast, &locator, settings, autofix, path))
             }
             Err(parse_error) => {
                 if settings.enabled.contains(&CheckCode::E999) {
diff --git a/src/pydocstyle/plugins.rs b/src/pydocstyle/plugins.rs
index c36377168c..1f81af1655 100644
--- a/src/pydocstyle/plugins.rs
+++ b/src/pydocstyle/plugins.rs
@@ -162,7 +162,7 @@ pub fn blank_before_after_function(checker: &mut Checker, definition: &Definitio
             } = &docstring.node
             {
                 if checker.settings.enabled.contains(&CheckCode::D201) {
-                    let (before, _, _) = checker.get_locator().partition_source_code_at(
+                    let (before, _, _) = checker.locator.partition_source_code_at(
                         &Range::from_located(parent),
                         &Range::from_located(docstring),
                     );
@@ -190,7 +190,7 @@ pub fn blank_before_after_function(checker: &mut Checker, definition: &Definitio
                 }
 
                 if checker.settings.enabled.contains(&CheckCode::D202) {
-                    let (_, _, after) = checker.get_locator().partition_source_code_at(
+                    let (_, _, after) = checker.locator.partition_source_code_at(
                         &Range::from_located(parent),
                         &Range::from_located(docstring),
                     );
@@ -253,7 +253,7 @@ pub fn blank_before_after_class(checker: &mut Checker, definition: &Definition)
                 if checker.settings.enabled.contains(&CheckCode::D203)
                     || checker.settings.enabled.contains(&CheckCode::D211)
                 {
-                    let (before, _, _) = checker.get_locator().partition_source_code_at(
+                    let (before, _, _) = checker.locator.partition_source_code_at(
                         &Range::from_located(parent),
                         &Range::from_located(docstring),
                     );
@@ -300,7 +300,7 @@ pub fn blank_before_after_class(checker: &mut Checker, definition: &Definition)
                 }
 
                 if checker.settings.enabled.contains(&CheckCode::D204) {
-                    let (_, _, after) = checker.get_locator().partition_source_code_at(
+                    let (_, _, after) = checker.locator.partition_source_code_at(
                         &Range::from_located(parent),
                         &Range::from_located(docstring),
                     );
@@ -530,7 +530,7 @@ pub fn newline_after_last_paragraph(checker: &mut Checker, definition: &Definiti
                 }
                 if line_count > 1 {
                     let content = checker
-                        .get_locator()
+                        .locator
                         .slice_source_code_range(&Range::from_located(docstring));
                     if let Some(last_line) = content.lines().last().map(|line| line.trim()) {
                         if last_line != "\"\"\"" && last_line != "'''" {
@@ -583,7 +583,7 @@ pub fn no_surrounding_whitespace(checker: &mut Checker, definition: &Definition)
                     );
                     if checker.patch() {
                         if let Some(first_line) = checker
-                            .get_locator()
+                            .locator
                             .slice_source_code_range(&Range::from_located(docstring))
                             .lines()
                             .next()
@@ -629,7 +629,7 @@ pub fn multi_line_summary_start(checker: &mut Checker, definition: &Definition)
         {
             if string.lines().nth(1).is_some() {
                 if let Some(first_line) = checker
-                    .get_locator()
+                    .locator
                     .slice_source_code_range(&Range::from_located(docstring))
                     .lines()
                     .next()
@@ -665,7 +665,7 @@ pub fn triple_quotes(checker: &mut Checker, definition: &Definition) {
         } = &docstring.node
         {
             if let Some(first_line) = checker
-                .get_locator()
+                .locator
                 .slice_source_code_range(&Range::from_located(docstring))
                 .lines()
                 .next()
diff --git a/src/pyupgrade/plugins/super_call_with_parameters.rs b/src/pyupgrade/plugins/super_call_with_parameters.rs
index b93f629250..31fe9c6c6f 100644
--- a/src/pyupgrade/plugins/super_call_with_parameters.rs
+++ b/src/pyupgrade/plugins/super_call_with_parameters.rs
@@ -17,9 +17,7 @@ pub fn super_call_with_parameters(checker: &mut Checker, expr: &Expr, func: &Exp
             .collect();
         if let Some(mut check) = checks::super_args(scope, &parents, expr, func, args) {
             if checker.patch() {
-                if let Some(fix) =
-                    pyupgrade::fixes::remove_super_arguments(checker.get_locator(), expr)
-                {
+                if let Some(fix) = pyupgrade::fixes::remove_super_arguments(checker.locator, expr) {
                     check.amend(fix);
                 }
             }
diff --git a/src/pyupgrade/plugins/useless_object_inheritance.rs b/src/pyupgrade/plugins/useless_object_inheritance.rs
index 073f6d18e6..c3cf4d23f8 100644
--- a/src/pyupgrade/plugins/useless_object_inheritance.rs
+++ b/src/pyupgrade/plugins/useless_object_inheritance.rs
@@ -15,7 +15,7 @@ pub fn useless_object_inheritance(
     if let Some(mut check) = checks::useless_object_inheritance(name, bases, scope) {
         if checker.patch() {
             if let Some(fix) = pyupgrade::fixes::remove_class_def_base(
-                checker.get_locator(),
+                checker.locator,
                 &stmt.location,
                 check.location,
                 bases,