From 2bd9f0f0205e03f95ab83e8f579742618b97a609 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Lauren=C8=9Biu=20Nicola?= <lnicola@dend.ro>
Date: Wed, 24 Jun 2020 12:57:28 +0300
Subject: Fix string literal inference in match

---
 crates/ra_hir_ty/src/infer/pat.rs      | 33 ++++++++++++--------
 crates/ra_hir_ty/src/tests/patterns.rs | 57 ++++++++++++++++++++++++++++++++++
 2 files changed, 77 insertions(+), 13 deletions(-)

diff --git a/crates/ra_hir_ty/src/infer/pat.rs b/crates/ra_hir_ty/src/infer/pat.rs
index 4006f595d..23de2bd6b 100644
--- a/crates/ra_hir_ty/src/infer/pat.rs
+++ b/crates/ra_hir_ty/src/infer/pat.rs
@@ -4,7 +4,7 @@ use std::iter::repeat;
 use std::sync::Arc;
 
 use hir_def::{
-    expr::{BindingAnnotation, Pat, PatId, RecordFieldPat},
+    expr::{BindingAnnotation, Expr, Literal, Pat, PatId, RecordFieldPat},
     path::Path,
     type_ref::Mutability,
     FieldId,
@@ -90,18 +90,7 @@ impl<'a> InferenceContext<'a> {
     ) -> Ty {
         let body = Arc::clone(&self.body); // avoid borrow checker problem
 
-        let is_non_ref_pat = match &body[pat] {
-            Pat::Tuple { .. }
-            | Pat::Or(..)
-            | Pat::TupleStruct { .. }
-            | Pat::Record { .. }
-            | Pat::Range { .. }
-            | Pat::Slice { .. } => true,
-            // FIXME: Path/Lit might actually evaluate to ref, but inference is unimplemented.
-            Pat::Path(..) | Pat::Lit(..) => true,
-            Pat::Wild | Pat::Bind { .. } | Pat::Ref { .. } | Pat::Missing => false,
-        };
-        if is_non_ref_pat {
+        if is_non_ref_pat(&body, pat) {
             while let Some((inner, mutability)) = expected.as_reference() {
                 expected = inner;
                 default_bm = match default_bm {
@@ -227,3 +216,21 @@ impl<'a> InferenceContext<'a> {
         ty
     }
 }
+
+fn is_non_ref_pat(body: &hir_def::body::Body, pat: PatId) -> bool {
+    match &body[pat] {
+        Pat::Tuple { .. }
+        | Pat::TupleStruct { .. }
+        | Pat::Record { .. }
+        | Pat::Range { .. }
+        | Pat::Slice { .. } => true,
+        Pat::Or(pats) => pats.iter().all(|p| is_non_ref_pat(body, *p)),
+        // FIXME: Path/Lit might actually evaluate to ref, but inference is unimplemented.
+        Pat::Path(..) => true,
+        Pat::Lit(expr) => match body[*expr] {
+            Expr::Literal(Literal::String(..)) => false,
+            _ => true,
+        },
+        Pat::Wild | Pat::Bind { .. } | Pat::Ref { .. } | Pat::Missing => false,
+    }
+}
diff --git a/crates/ra_hir_ty/src/tests/patterns.rs b/crates/ra_hir_ty/src/tests/patterns.rs
index 8fa296137..e5ef241ca 100644
--- a/crates/ra_hir_ty/src/tests/patterns.rs
+++ b/crates/ra_hir_ty/src/tests/patterns.rs
@@ -270,6 +270,63 @@ fn test() {
     );
 }
 
+#[test]
+fn infer_pattern_match_string_literal() {
+    assert_snapshot!(
+        infer_with_mismatches(r#"
+fn test() {
+    let s: &str = "hello";
+    match s {
+        "hello" => {}
+        _ => {}
+    }
+}
+"#, true),
+    @r###"
+    10..98 '{     ...   } }': ()
+    20..21 's': &str
+    30..37 '"hello"': &str
+    43..96 'match ...     }': ()
+    49..50 's': &str
+    61..68 '"hello"': &str
+    61..68 '"hello"': &str
+    72..74 '{}': ()
+    83..84 '_': &str
+    88..90 '{}': ()
+    "###
+    );
+}
+
+#[test]
+fn infer_pattern_match_or() {
+    assert_snapshot!(
+        infer_with_mismatches(r#"
+fn test() {
+    let s: &str = "hello";
+    match s {
+        "hello" | "world" => {}
+        _ => {}
+    }
+}
+"#, true),
+    @r###"
+    10..108 '{     ...   } }': ()
+    20..21 's': &str
+    30..37 '"hello"': &str
+    43..106 'match ...     }': ()
+    49..50 's': &str
+    61..68 '"hello"': &str
+    61..68 '"hello"': &str
+    61..78 '"hello...world"': &str
+    71..78 '"world"': &str
+    71..78 '"world"': &str
+    82..84 '{}': ()
+    93..94 '_': &str
+    98..100 '{}': ()
+    "###
+    );
+}
+
 #[test]
 fn infer_pattern_match_arr() {
     assert_snapshot!(
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