perf: less allocations when using string patterns (#11255)

This PR reduces the allocations when using string patterns. In
particular
`startsWith`, `dropPrefix?`, `endsWith`, `dropSuffix?` are optimized.

Author: hargoniX

src/Init/Data/String/Defs.lean

@@ -435,7 +435,7 @@ theorem endExclusive_toSlice {s : String} : s.toSlice.endExclusive = s.endValidP
 theorem str_toSlice {s : String} : s.toSlice.str = s := rfl
 
 /-- The number of bytes of the UTF-8 encoding of the string slice. -/
-@[expose]
+@[expose, inline]
 def Slice.utf8ByteSize (s : Slice) : Nat :=
   s.startInclusive.offset.byteDistance s.endExclusive.offset
 
@@ -464,7 +464,7 @@ theorem Pos.Raw.byteIdx_sub_slice {p : Pos.Raw} {s : Slice} :
     (p - s).byteIdx = p.byteIdx - s.utf8ByteSize := rfl
 
 /-- The end position of a slice, as a `Pos.Raw`. -/
-@[expose]
+@[expose, inline]
 def Slice.rawEndPos (s : Slice) : Pos.Raw where
   byteIdx := s.utf8ByteSize
 

src/Init/Data/String/Pattern/Basic.lean

@@ -74,8 +74,8 @@ class ForwardPattern (ρ : Type) where
 
 namespace Internal
 
-@[extern "lean_slice_memcmp"]
-def memcmp (lhs rhs : @& Slice) (lstart : @& String.Pos.Raw) (rstart : @& String.Pos.Raw)
+@[extern "lean_string_memcmp"]
+def memcmpStr (lhs rhs : @& String) (lstart : @& String.Pos.Raw) (rstart : @& String.Pos.Raw)
     (len : @& String.Pos.Raw) (h1 : len.offsetBy lstart ≤ lhs.rawEndPos)
     (h2 : len.offsetBy rstart ≤ rhs.rawEndPos) : Bool :=
   go 0
@@ -99,6 +99,27 @@ where
     simp [Pos.Raw.lt_iff] at h ⊢
     omega
 
+@[inline]
+def memcmpSlice (lhs rhs : Slice) (lstart : String.Pos.Raw) (rstart : String.Pos.Raw)
+    (len : String.Pos.Raw) (h1 : len.offsetBy lstart ≤ lhs.rawEndPos)
+    (h2 : len.offsetBy rstart ≤ rhs.rawEndPos) : Bool :=
+  memcmpStr
+    lhs.str
+    rhs.str
+    (lstart.offsetBy lhs.startInclusive.offset)
+    (rstart.offsetBy rhs.startInclusive.offset)
+    len
+    (by
+      have := lhs.startInclusive_le_endExclusive
+      have := lhs.endExclusive.isValid.le_utf8ByteSize
+      simp [ValidPos.le_iff, Pos.Raw.le_iff, Slice.utf8ByteSize_eq] at *
+      omega)
+    (by
+      have := rhs.startInclusive_le_endExclusive
+      have := rhs.endExclusive.isValid.le_utf8ByteSize
+      simp [ValidPos.le_iff, Pos.Raw.le_iff, Slice.utf8ByteSize_eq] at *
+      omega)
+
 end Internal
 
 namespace ForwardPattern

src/Init/Data/String/Pattern/String.lean

@@ -270,7 +270,7 @@ def startsWith (s : Slice) (pat : Slice) : Bool :=
       omega
     have hp := by
       simp [Pos.Raw.le_iff]
-    Internal.memcmp s pat s.startPos.offset pat.startPos.offset pat.rawEndPos hs hp
+    Internal.memcmpSlice s pat s.startPos.offset pat.startPos.offset pat.rawEndPos hs hp
   else
     false
 
@@ -306,7 +306,7 @@ def endsWith (s : Slice) (pat : Slice) : Bool :=
       omega
     have hp := by
       simp [patStart, Pos.Raw.le_iff] at h ⊢
-    Internal.memcmp s pat sStart patStart pat.rawEndPos hs hp
+    Internal.memcmpSlice s pat sStart patStart pat.rawEndPos hs hp
   else
     false
 

src/Init/Data/String/Slice.lean

@@ -68,7 +68,7 @@ def beq (s1 s2 : Slice) : Bool :=
   if h : s1.utf8ByteSize = s2.utf8ByteSize then
     have h1 := by simp [h, String.Pos.Raw.le_iff]
     have h2 := by simp [h, String.Pos.Raw.le_iff]
-    Internal.memcmp s1 s2 s1.startPos.offset s2.startPos.offset s1.rawEndPos h1 h2
+    Internal.memcmpSlice s1 s2 s1.startPos.offset s2.startPos.offset s1.rawEndPos h1 h2
   else
     false
 

src/include/lean/lean.h

@@ -1163,7 +1163,7 @@ static inline uint8_t lean_string_dec_eq(b_lean_obj_arg s1, b_lean_obj_arg s2) {
 static inline uint8_t lean_string_dec_lt(b_lean_obj_arg s1, b_lean_obj_arg s2) { return lean_string_lt(s1, s2); }
 LEAN_EXPORT uint64_t lean_string_hash(b_lean_obj_arg);
 LEAN_EXPORT lean_obj_res lean_string_of_usize(size_t);
-LEAN_EXPORT uint8_t lean_slice_memcmp(b_lean_obj_arg s1, b_lean_obj_arg s2, b_lean_obj_arg lstart, b_lean_obj_arg rstart, b_lean_obj_arg len);
+LEAN_EXPORT uint8_t lean_string_memcmp(b_lean_obj_arg s1, b_lean_obj_arg s2, b_lean_obj_arg lstart, b_lean_obj_arg rstart, b_lean_obj_arg len);
 LEAN_EXPORT uint64_t lean_slice_hash(b_lean_obj_arg);
 LEAN_EXPORT uint8_t lean_slice_dec_lt(b_lean_obj_arg s1, b_lean_obj_arg s2);
 

src/lake/Lake/Util/FilePath.lean

@@ -82,13 +82,4 @@ where
         removeExts s i' e
   termination_by i.1
 
--- sanity check
-example :
-  modOfFilePath "Foo/Bar" = `Foo.Bar
-  ∧ modOfFilePath "Foo/Bar/" = `Foo.Bar
-  ∧ modOfFilePath "Foo/Bar.lean" = `Foo.Bar
-  ∧ modOfFilePath "Foo/Bar.tar.gz" = `Foo.Bar
-  ∧ modOfFilePath "Foo/Bar.lean/" = `Foo.«Bar.lean»
-:= by native_decide
-
 attribute [deprecated "Deprecated without replacement." (since := "2025-08-01")] modOfFilePath

src/runtime/object.cpp

@@ -2362,6 +2362,17 @@ extern "C" LEAN_EXPORT obj_res lean_string_of_usize(size_t n) {
     return mk_ascii_string_unchecked(std::to_string(n));
 }
 
+extern "C" LEAN_EXPORT uint8_t lean_string_memcmp(b_obj_arg s1, b_obj_arg s2, b_obj_arg lstart, b_obj_arg rstart, b_obj_arg len) {
+    // Thanks to the proof arguments we know that lstart, rstart and len are all scalars.
+    lean_assert(lean_is_scalar(lstart));
+    lean_assert(lean_is_scalar(rstart));
+    lean_assert(lean_is_scalar(len));
+
+    char const * lbase = lean_string_cstr(s1) + lean_unbox(lstart);
+    char const * rbase = lean_string_cstr(s2) + lean_unbox(rstart);
+    return std::memcmp(lbase, rbase, lean_unbox(len)) == 0;
+}
+
 size_t lean_slice_size(b_obj_arg slice) {
    b_obj_res start = lean_ctor_get(slice, 1);
    lean_assert(lean_is_scalar(start));
@@ -2377,17 +2388,6 @@ char const * lean_slice_base(b_obj_arg slice) {
    return lean_string_cstr(string) + lean_unbox(offset);
 }
 
-extern "C" LEAN_EXPORT uint8_t lean_slice_memcmp(b_obj_arg s1, b_obj_arg s2, b_obj_arg lstart, b_obj_arg rstart, b_obj_arg len) {
-    // Thanks to the proof arguments we know that lstart, rstart and len are all scalars.
-    lean_assert(lean_is_scalar(lstart));
-    lean_assert(lean_is_scalar(rstart));
-    lean_assert(lean_is_scalar(len));
-
-    char const * lbase = lean_slice_base(s1) + lean_unbox(lstart);
-    char const * rbase = lean_slice_base(s2) + lean_unbox(rstart);
-    return std::memcmp(lbase, rbase, lean_unbox(len)) == 0;
-}
-
 extern "C" LEAN_EXPORT uint64_t lean_slice_hash(b_obj_arg s) {
     size_t sz = lean_slice_size(s);
     char const * str = lean_slice_base(s);

stage0/src/stdlib_flags.h

@@ -11,7 +11,7 @@ options get_default_options() {
     opts = opts.update({"debug", "terminalTacticsAsSorry"}, false);
     // switch to `true` for ABI-breaking changes affecting meta code;
     // see also next option!
-    opts = opts.update({"interpreter", "prefer_native"}, false);
+    opts = opts.update({"interpreter", "prefer_native"}, true);
     // switch to `false` when enabling `prefer_native` should also affect use
     // of built-in parsers in quotations; this is usually the case, but setting
     // both to `true` may be necessary for handling non-builtin parsers with