diff --git a/clippy_lints/src/strings.rs b/clippy_lints/src/strings.rs
index 509ad4e4fcb3..d14a56115cbd 100644
--- a/clippy_lints/src/strings.rs
+++ b/clippy_lints/src/strings.rs
@@ -417,6 +417,8 @@ impl<'tcx> LateLintPass<'tcx> for StrToString {
             && args.iter().any(|a| a.hir_id == expr.hir_id)
             && let Res::Def(DefKind::AssocFn, def_id) = expr.res(cx)
             && cx.tcx.is_diagnostic_item(sym::to_string_method, def_id)
+            && let Some(args) = cx.typeck_results().node_args_opt(expr.hir_id)
+            && args.type_at(0).is_str()
         {
             // Detected `ToString::to_string` passed as an argument (generic: any call or method call)
             span_lint_and_sugg(
@@ -425,7 +427,7 @@ impl<'tcx> LateLintPass<'tcx> for StrToString {
                 expr.span,
                 "`ToString::to_string` used as `&str` to `String` converter",
                 "try",
-                "ToOwned::to_owned".to_string(),
+                "str::to_owned".to_string(),
                 Applicability::MachineApplicable,
             );
         }
diff --git a/tests/ui/str_to_string.fixed b/tests/ui/str_to_string.fixed
index 5b76cf78f069..a8950ab70e56 100644
--- a/tests/ui/str_to_string.fixed
+++ b/tests/ui/str_to_string.fixed
@@ -1,10 +1,10 @@
 #![warn(clippy::str_to_string)]
 
 fn main() {
-    let hello = "hello world".to_owned();
+    let hello: String = "hello world".to_owned();
     //~^ str_to_string
 
-    let msg = &hello[..];
+    let msg: &str = &hello[..];
     msg.to_owned();
     //~^ str_to_string
 }
@@ -19,7 +19,7 @@ fn issue16271(key: &[u8]) {
         };
     }
 
-    let _value = t!(str::from_utf8(key)).to_owned();
+    let _value: String = t!(str::from_utf8(key)).to_owned();
     //~^ str_to_string
 }
 
@@ -32,22 +32,27 @@ impl<T> GenericWrapper<T> {
 }
 
 fn issue16511(x: Option<&str>) {
-    let _ = x.map(ToOwned::to_owned);
+    let _: Option<String> = x.map(str::to_owned);
     //~^ str_to_string
 
-    let _ = x.map(ToOwned::to_owned);
+    let _: Option<String> = x.map(str::to_owned);
     //~^ str_to_string
 
-    let _ = ["a", "b"].iter().map(ToOwned::to_owned);
-    //~^ str_to_string
+    // This should not trigger the lint because ToOwned::to_owned would produce &str, not String.
+    let _: Vec<String> = ["a", "b"].iter().map(ToString::to_string).collect();
 
     fn mapper<F: Fn(&str) -> String>(f: F) -> String {
         f("hello")
     }
-    let _ = mapper(ToOwned::to_owned);
+    let _: String = mapper(str::to_owned);
     //~^ str_to_string
 
-    let w = GenericWrapper("hello");
-    let _ = w.mapper(ToOwned::to_owned);
+    let w: GenericWrapper<&str> = GenericWrapper("hello");
+    let _: String = w.mapper(str::to_owned);
     //~^ str_to_string
 }
+
+// No lint: non-str types should not trigger str_to_string. See #16569
+fn no_lint_non_str() {
+    let _: Vec<String> = [1, 2].iter().map(i32::to_string).collect();
+}
diff --git a/tests/ui/str_to_string.rs b/tests/ui/str_to_string.rs
index f099eb29b1b5..5d78893f53f6 100644
--- a/tests/ui/str_to_string.rs
+++ b/tests/ui/str_to_string.rs
@@ -1,10 +1,10 @@
 #![warn(clippy::str_to_string)]
 
 fn main() {
-    let hello = "hello world".to_string();
+    let hello: String = "hello world".to_string();
     //~^ str_to_string
 
-    let msg = &hello[..];
+    let msg: &str = &hello[..];
     msg.to_string();
     //~^ str_to_string
 }
@@ -19,7 +19,7 @@ fn issue16271(key: &[u8]) {
         };
     }
 
-    let _value = t!(str::from_utf8(key)).to_string();
+    let _value: String = t!(str::from_utf8(key)).to_string();
     //~^ str_to_string
 }
 
@@ -32,22 +32,27 @@ impl<T> GenericWrapper<T> {
 }
 
 fn issue16511(x: Option<&str>) {
-    let _ = x.map(ToString::to_string);
+    let _: Option<String> = x.map(ToString::to_string);
     //~^ str_to_string
 
-    let _ = x.map(str::to_string);
+    let _: Option<String> = x.map(str::to_string);
     //~^ str_to_string
 
-    let _ = ["a", "b"].iter().map(ToString::to_string);
-    //~^ str_to_string
+    // This should not trigger the lint because ToOwned::to_owned would produce &str, not String.
+    let _: Vec<String> = ["a", "b"].iter().map(ToString::to_string).collect();
 
     fn mapper<F: Fn(&str) -> String>(f: F) -> String {
         f("hello")
     }
-    let _ = mapper(ToString::to_string);
+    let _: String = mapper(ToString::to_string);
     //~^ str_to_string
 
-    let w = GenericWrapper("hello");
-    let _ = w.mapper(ToString::to_string);
+    let w: GenericWrapper<&str> = GenericWrapper("hello");
+    let _: String = w.mapper(ToString::to_string);
     //~^ str_to_string
 }
+
+// No lint: non-str types should not trigger str_to_string. See #16569
+fn no_lint_non_str() {
+    let _: Vec<String> = [1, 2].iter().map(i32::to_string).collect();
+}
diff --git a/tests/ui/str_to_string.stderr b/tests/ui/str_to_string.stderr
index 296b8e36f28c..cd4db83e6370 100644
--- a/tests/ui/str_to_string.stderr
+++ b/tests/ui/str_to_string.stderr
@@ -1,8 +1,8 @@
 error: `to_string()` called on a `&str`
-  --> tests/ui/str_to_string.rs:4:17
+  --> tests/ui/str_to_string.rs:4:25
    |
-LL |     let hello = "hello world".to_string();
-   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `"hello world".to_owned()`
+LL |     let hello: String = "hello world".to_string();
+   |                         ^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `"hello world".to_owned()`
    |
    = note: `-D clippy::str-to-string` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(clippy::str_to_string)]`
@@ -14,40 +14,34 @@ LL |     msg.to_string();
    |     ^^^^^^^^^^^^^^^ help: try: `msg.to_owned()`
 
 error: `to_string()` called on a `&str`
-  --> tests/ui/str_to_string.rs:22:18
+  --> tests/ui/str_to_string.rs:22:26
    |
-LL |     let _value = t!(str::from_utf8(key)).to_string();
-   |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `t!(str::from_utf8(key)).to_owned()`
+LL |     let _value: String = t!(str::from_utf8(key)).to_string();
+   |                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `t!(str::from_utf8(key)).to_owned()`
 
 error: `ToString::to_string` used as `&str` to `String` converter
-  --> tests/ui/str_to_string.rs:35:19
+  --> tests/ui/str_to_string.rs:35:35
    |
-LL |     let _ = x.map(ToString::to_string);
-   |                   ^^^^^^^^^^^^^^^^^^^ help: try: `ToOwned::to_owned`
+LL |     let _: Option<String> = x.map(ToString::to_string);
+   |                                   ^^^^^^^^^^^^^^^^^^^ help: try: `str::to_owned`
 
 error: `ToString::to_string` used as `&str` to `String` converter
-  --> tests/ui/str_to_string.rs:38:19
+  --> tests/ui/str_to_string.rs:38:35
    |
-LL |     let _ = x.map(str::to_string);
-   |                   ^^^^^^^^^^^^^^ help: try: `ToOwned::to_owned`
+LL |     let _: Option<String> = x.map(str::to_string);
+   |                                   ^^^^^^^^^^^^^^ help: try: `str::to_owned`
 
 error: `ToString::to_string` used as `&str` to `String` converter
-  --> tests/ui/str_to_string.rs:41:35
+  --> tests/ui/str_to_string.rs:47:28
    |
-LL |     let _ = ["a", "b"].iter().map(ToString::to_string);
-   |                                   ^^^^^^^^^^^^^^^^^^^ help: try: `ToOwned::to_owned`
+LL |     let _: String = mapper(ToString::to_string);
+   |                            ^^^^^^^^^^^^^^^^^^^ help: try: `str::to_owned`
 
 error: `ToString::to_string` used as `&str` to `String` converter
-  --> tests/ui/str_to_string.rs:47:20
+  --> tests/ui/str_to_string.rs:51:30
    |
-LL |     let _ = mapper(ToString::to_string);
-   |                    ^^^^^^^^^^^^^^^^^^^ help: try: `ToOwned::to_owned`
+LL |     let _: String = w.mapper(ToString::to_string);
+   |                              ^^^^^^^^^^^^^^^^^^^ help: try: `str::to_owned`
 
-error: `ToString::to_string` used as `&str` to `String` converter
-  --> tests/ui/str_to_string.rs:51:22
-   |
-LL |     let _ = w.mapper(ToString::to_string);
-   |                      ^^^^^^^^^^^^^^^^^^^ help: try: `ToOwned::to_owned`
-
-error: aborting due to 8 previous errors
+error: aborting due to 7 previous errors