diff --git a/Makefile b/Makefile
index 03a1aafd34ff..7e8070d16921 100644
--- a/Makefile
+++ b/Makefile
@@ -139,31 +139,9 @@ llvm_ext: $(LLVM_EXT_OBJ)
 format: ## Format sources
 	./bin/crystal tool format$(if $(check), --check) src spec samples scripts
 
-generate_data: ## Run generator scripts for Unicode, SSL config, ... (usually with `-B`/`--always-make` flag)
-
-generate_data: spec/std/string/graphemes_break_spec.cr
-spec/std/string/graphemes_break_spec.cr: scripts/generate_grapheme_break_specs.cr
-	$(CRYSTAL) run $<
-
-generate_data: src/string/grapheme/properties.cr
-src/string/grapheme/properties.cr: scripts/generate_grapheme_properties.cr
-	$(CRYSTAL) run $<
-
-generate_data: src/openssl/ssl/defaults.cr
-src/openssl/ssl/defaults.cr: scripts/generate_ssl_server_defaults.cr
-	$(CRYSTAL) run $<
-
-generate_data: src/unicode/data.cr
-src/unicode/data.cr: scripts/generate_unicode_data.cr
-	$(CRYSTAL) run $<
-
-generate_data: src/crystal/system/win32/zone_names.cr
-src/crystal/system/win32/zone_names.cr: scripts/generate_windows_zone_names.cr
-	$(CRYSTAL) run $<
-
-generate_data: src/html/entities.cr
-src/html/entities.cr: scripts/generate_html_entities.cr scripts/html_entities.ecr
-	$(CRYSTAL) run $<
+.PHONY: generate_data
+generate_data: ## Run generator scripts for Unicode, SSL config, ...
+	$(MAKE) -B -f scripts/generate_data.mk
 
 .PHONY: install
 install: $(O)/crystal man/crystal.1.gz ## Install the compiler at DESTDIR
diff --git a/Makefile.win b/Makefile.win
index 595a26f5fd00..e2b18741657e 100644
--- a/Makefile.win
+++ b/Makefile.win
@@ -35,7 +35,7 @@ static ?=       ## Enable static linking
 target ?=       ## Cross-compilation target
 interpreter ?=  ## Enable interpreter feature
 check ?=        ## Enable only check when running format
-order ?=        ## Enable order for spec execution (values: "default" | "random" | seed number)
+order ?=random  ## Enable order for spec execution (values: "default" | "random" | seed number)
 
 MAKEFLAGS += --no-builtin-rules
 .SUFFIXES:
@@ -141,31 +141,9 @@ llvm_ext: $(LLVM_EXT_OBJ)
 format: ## Format sources
 	.\bin\crystal tool format$(if $(check), --check) src spec samples scripts
 
-generate_data: ## Run generator scripts for Unicode, SSL config, ... (usually with `-B`/`--always-make` flag)
-
-generate_data: spec\std\string\graphemes_break_spec.cr
-spec\std\string\graphemes_break_spec.cr: scripts\generate_grapheme_break_specs.cr
-	$(CRYSTAL) run $<
-
-generate_data: src\string\grapheme\properties.cr
-src\string\grapheme\properties.cr: scripts\generate_grapheme_properties.cr
-	$(CRYSTAL) run $<
-
-generate_data: src\openssl\ssl\defaults.cr
-src\openssl\ssl\defaults.cr: scripts\generate_ssl_server_defaults.cr
-	$(CRYSTAL) run $<
-
-generate_data: src\unicode\data.cr
-src\unicode\data.cr: scripts\generate_unicode_data.cr
-	$(CRYSTAL) run $<
-
-generate_data: src\crystal\system\win32\zone_names.cr
-src\crystal\system\win32\zone_names.cr: scripts\generate_windows_zone_names.cr
-	$(CRYSTAL) run $<
-
-generate_data: src\html\entities.cr
-src\html\entities.cr: scripts\generate_html_entities.cr scripts\html_entities.ecr
-	$(CRYSTAL) run $<
+.PHONY: generate_data
+generate_data: ## Run generator scripts for Unicode, SSL config, ...
+	$(MAKE) -B -f scripts/generate_data.mk
 
 .PHONY: install
 install: $(O)\crystal.exe ## Install the compiler at prefix
diff --git a/scripts/generate_data.mk b/scripts/generate_data.mk
new file mode 100644
index 000000000000..ad04f0fd0c82
--- /dev/null
+++ b/scripts/generate_data.mk
@@ -0,0 +1,37 @@
+
+## Run all data generators
+##   $ make -f scripts/generate_data.mk
+
+ifeq ($(OS),Windows_NT)
+  BIN_CRYSTAL=bin\crystal
+else
+  BIN_CRYSTAL=bin/crystal
+endif
+
+.PHONY: all
+all: ## Run all generators
+	$(BIN_CRYSTAL) run scripts/generate_grapheme_break_specs.cr
+	$(BIN_CRYSTAL) run scripts/generate_grapheme_properties.cr
+	$(BIN_CRYSTAL) run scripts/generate_ssl_server_defaults.cr
+	$(BIN_CRYSTAL) run scripts/generate_unicode_data.cr
+	$(BIN_CRYSTAL) run scripts/generate_windows_zone_names.cr
+	$(BIN_CRYSTAL) run scripts/generate_html_entities.cr
+
+ifneq ($(OS),Windows_NT)
+.PHONY: help
+help: ## Show this help
+	@echo
+	@printf '\033[34mtargets:\033[0m\n'
+	@grep -hE '^[a-zA-Z_-]+:.*?## .*$$' $(MAKEFILE_LIST) |\
+		sort |\
+		awk 'BEGIN {FS = ":.*?## "}; {printf "  \033[36m%-15s\033[0m %s\n", $$1, $$2}'
+	@echo
+	@printf '\033[34moptional variables:\033[0m\n'
+	@grep -hE '^[a-zA-Z_-]+ \?=.*?## .*$$' $(MAKEFILE_LIST) |\
+		sort |\
+		awk 'BEGIN {FS = " \\?=.*?## "}; {printf "  \033[36m%-15s\033[0m %s\n", $$1, $$2}'
+	@echo
+	@printf '\033[34mrecipes:\033[0m\n'
+	@grep -hE '^##.*$$' $(MAKEFILE_LIST) |\
+		awk 'BEGIN {FS = "## "}; /^## [a-zA-Z_-]/ {printf "  \033[36m%s\033[0m\n", $$2}; /^##  / {printf "  %s\n", $$2}'
+endif
diff --git a/spec/compiler/interpreter/sizeof_spec.cr b/spec/compiler/interpreter/sizeof_spec.cr
index 4eb5216b28e5..4c52247b9687 100644
--- a/spec/compiler/interpreter/sizeof_spec.cr
+++ b/spec/compiler/interpreter/sizeof_spec.cr
@@ -7,4 +7,16 @@ describe Crystal::Repl::Interpreter do
       interpret("sizeof(typeof(1))").should eq(4)
     end
   end
+
+  context "instance_sizeof" do
+    it "interprets instance_sizeof typeof" do
+      interpret(<<-CRYSTAL).should eq(16)
+        class Foo
+          @x = 0_i64
+        end
+
+        instance_sizeof(typeof(Foo.new))
+        CRYSTAL
+    end
+  end
 end
diff --git a/spec/compiler/semantic/c_type_spec.cr b/spec/compiler/semantic/c_type_spec.cr
index dd034ae231e7..cb2e367a9593 100644
--- a/spec/compiler/semantic/c_type_spec.cr
+++ b/spec/compiler/semantic/c_type_spec.cr
@@ -2,24 +2,50 @@ require "../../spec_helper"
 
 describe "Semantic: type" do
   it "can call methods of original type" do
-    assert_type("
+    assert_type(<<-CRYSTAL, inject_primitives: true) { uint64 }
       lib Lib
         type X = Void*
         fun foo : X
       end
 
       Lib.foo.address
-    ", inject_primitives: true) { uint64 }
+      CRYSTAL
   end
 
   it "can call methods of parent type" do
-    assert_error("
+    assert_error(<<-CRYSTAL, "undefined method 'baz'")
       lib Lib
         type X = Void*
         fun foo : X
       end
 
       Lib.foo.baz
-    ", "undefined method 'baz'")
+      CRYSTAL
+  end
+
+  it "can access instance variables of original type" do
+    assert_type(<<-CRYSTAL) { int32 }
+      lib Lib
+        struct X
+          x : Int32
+        end
+
+        type Y = X
+        fun foo : Y
+      end
+
+      Lib.foo.@x
+      CRYSTAL
+  end
+
+  it "errors if original type doesn't support instance variables" do
+    assert_error(<<-CRYSTAL, "can't use instance variables inside primitive types (at Int32)")
+      lib Lib
+        type X = Int32
+        fun foo : X
+      end
+
+      Lib.foo.@x
+      CRYSTAL
   end
 end
diff --git a/spec/std/big/big_int_spec.cr b/spec/std/big/big_int_spec.cr
index 8a86939efbac..68eba643a571 100644
--- a/spec/std/big/big_int_spec.cr
+++ b/spec/std/big/big_int_spec.cr
@@ -283,6 +283,34 @@ describe "BigInt" do
     -5.to_big_i.remainder(-3).should eq(-2)
   end
 
+  it "#bit" do
+    x = 123.to_big_i
+    x.bit(-10.to_big_i ** 99).should eq(0)
+    x.bit(-(2.to_big_i ** 64)).should eq(0)
+    x.bit(-1).should eq(0)
+    x.bit(0).should eq(1)
+    x.bit(2).should eq(0)
+    x.bit(3).should eq(1)
+    x.bit(6).should eq(1)
+    x.bit(7).should eq(0)
+    x.bit(64).should eq(0)
+    x.bit(2.to_big_i ** 64).should eq(0)
+    x.bit(10.to_big_i ** 99).should eq(0)
+
+    x = ~(123.to_big_i)
+    x.bit(-10.to_big_i ** 99).should eq(0)
+    x.bit(-(2.to_big_i ** 64)).should eq(0)
+    x.bit(-1).should eq(0)
+    x.bit(0).should eq(0)
+    x.bit(2).should eq(1)
+    x.bit(3).should eq(0)
+    x.bit(6).should eq(0)
+    x.bit(7).should eq(1)
+    x.bit(64).should eq(1)
+    x.bit(2.to_big_i ** 64).should eq(1)
+    x.bit(10.to_big_i ** 99).should eq(1)
+  end
+
   it "does bitwise and" do
     (123.to_big_i & 321).should eq(65)
     (BigInt.new("96238761238973286532") & 86325735648).should eq(69124358272)
diff --git a/spec/std/file_spec.cr b/spec/std/file_spec.cr
index 53d28bdcee4e..3c020fee36a1 100644
--- a/spec/std/file_spec.cr
+++ b/spec/std/file_spec.cr
@@ -941,7 +941,7 @@ describe "File" do
             pending! "Spec cannot run as superuser"
           end
         {% end %}
-        expect_raises(File::AccessDeniedError) { File.read(path) }
+        expect_raises(File::AccessDeniedError, "Error opening file with mode 'r': '#{path.inspect_unquoted}'") { File.read(path) }
       end
     end
   {% end %}
@@ -958,7 +958,7 @@ describe "File" do
           pending! "Spec cannot run as superuser"
         end
       {% end %}
-      expect_raises(File::AccessDeniedError) { File.write(path, "foo") }
+      expect_raises(File::AccessDeniedError, "Error opening file with mode 'w': '#{path.inspect_unquoted}'") { File.write(path, "foo") }
     end
   end
 
diff --git a/spec/std/string_spec.cr b/spec/std/string_spec.cr
index 8a372a370677..178fa81a172c 100644
--- a/spec/std/string_spec.cr
+++ b/spec/std/string_spec.cr
@@ -2343,6 +2343,33 @@ describe "String" do
     "foo".matches?(/bar/).should eq(false)
   end
 
+  it "#matches_full?" do
+    pending! if {{ Regex::Engine.resolve.name == "Regex::PCRE" }}
+    "foo".matches_full?(/foo/).should be_true
+    "fooo".matches_full?(/foo/).should be_false
+    "ofoo".matches_full?(/foo/).should be_false
+    "pattern".matches_full?(/(\A)?pattern(\z)?/).should be_true
+    "_pattern_".matches_full?(/(\A)?pattern(\z)?/).should be_false
+  end
+
+  it "#match_full" do
+    pending! if {{ Regex::Engine.resolve.name == "Regex::PCRE" }}
+    "foo".match_full(/foo/).not_nil![0].should eq "foo"
+    "fooo".match_full(/foo/).should be_nil
+    "ofoo".match_full(/foo/).should be_nil
+    "pattern".match_full(/(\A)?pattern(\z)?/).not_nil![0].should eq "pattern"
+    "_pattern_".match_full(/(\A)?pattern(\z)?/).should be_nil
+  end
+
+  it "#match_full!" do
+    pending! if {{ Regex::Engine.resolve.name == "Regex::PCRE" }}
+    "foo".match_full!(/foo/).not_nil![0].should eq "foo"
+    expect_raises(Regex::Error) { "fooo".match_full!(/foo/) }
+    expect_raises(Regex::Error) { "ofoo".match_full!(/foo/) }
+    "pattern".match_full!(/(\A)?pattern(\z)?/).not_nil![0].should eq "pattern"
+    expect_raises(Regex::Error) { "_pattern_".match_full!(/(\A)?pattern(\z)?/) }
+  end
+
   it "has size (same as size)" do
     "テスト".size.should eq(3)
   end
diff --git a/src/big/big_int.cr b/src/big/big_int.cr
index b0530c7b7592..e6b5f0214297 100644
--- a/src/big/big_int.cr
+++ b/src/big/big_int.cr
@@ -385,6 +385,12 @@ struct BigInt < Int
     BigInt.new { |mpz| LibGMP.com(mpz, self) }
   end
 
+  def bit(bit : Int)
+    return 0 if bit < 0
+    return self < 0 ? 1 : 0 if bit > LibGMP::BitcntT::MAX
+    LibGMP.tstbit(self, LibGMP::BitcntT.new!(bit))
+  end
+
   def &(other : BigInt) : BigInt
     BigInt.new { |mpz| LibGMP.and(mpz, self, other) }
   end
diff --git a/src/big/lib_gmp.cr b/src/big/lib_gmp.cr
index 9caf408f1494..3cae0de64b77 100644
--- a/src/big/lib_gmp.cr
+++ b/src/big/lib_gmp.cr
@@ -116,6 +116,8 @@ lib LibGMP
   fun xor = __gmpz_xor(rop : MPZ*, op1 : MPZ*, op2 : MPZ*)
   fun com = __gmpz_com(rop : MPZ*, op : MPZ*)
 
+  fun tstbit = __gmpz_tstbit(op : MPZ*, bit_index : BitcntT) : Int
+
   fun fdiv_q_2exp = __gmpz_fdiv_q_2exp(q : MPZ*, n : MPZ*, b : BitcntT)
   fun mul_2exp = __gmpz_mul_2exp(rop : MPZ*, op1 : MPZ*, op2 : BitcntT)
 
diff --git a/src/compiler/crystal/interpreter/compiler.cr b/src/compiler/crystal/interpreter/compiler.cr
index 1faf5db32bb6..03d7430a0fe6 100644
--- a/src/compiler/crystal/interpreter/compiler.cr
+++ b/src/compiler/crystal/interpreter/compiler.cr
@@ -1422,6 +1422,14 @@ class Crystal::Repl::Compiler < Crystal::Visitor
     false
   end
 
+  def visit(node : InstanceSizeOf)
+    return false unless @wants_value
+
+    put_i32 inner_instance_sizeof_type(node.exp), node: node
+
+    false
+  end
+
   def visit(node : TypeNode)
     return false unless @wants_value
 
@@ -3361,25 +3369,8 @@ class Crystal::Repl::Compiler < Crystal::Visitor
     @instructions.instructions.size
   end
 
-  private def aligned_sizeof_type(node : ASTNode) : Int32
-    @context.aligned_sizeof_type(node)
-  end
-
-  private def aligned_sizeof_type(type : Type?) : Int32
-    @context.aligned_sizeof_type(type)
-  end
-
-  private def inner_sizeof_type(node : ASTNode) : Int32
-    @context.inner_sizeof_type(node)
-  end
-
-  private def inner_sizeof_type(type : Type?) : Int32
-    @context.inner_sizeof_type(type)
-  end
-
-  private def aligned_instance_sizeof_type(type : Type) : Int32
-    @context.aligned_instance_sizeof_type(type)
-  end
+  private delegate inner_sizeof_type, aligned_sizeof_type,
+    inner_instance_sizeof_type, aligned_instance_sizeof_type, to: @context
 
   private def ivar_offset(type : Type, name : String) : Int32
     if type.extern_union?
diff --git a/src/compiler/crystal/interpreter/context.cr b/src/compiler/crystal/interpreter/context.cr
index e91b615713f2..268d67448125 100644
--- a/src/compiler/crystal/interpreter/context.cr
+++ b/src/compiler/crystal/interpreter/context.cr
@@ -316,7 +316,19 @@ class Crystal::Repl::Context
   end
 
   def aligned_instance_sizeof_type(type : Type) : Int32
-    align(@program.instance_size_of(type.sizeof_type).to_i32)
+    align(inner_instance_sizeof_type(type))
+  end
+
+  def inner_instance_sizeof_type(node : ASTNode) : Int32
+    inner_instance_sizeof_type(node.type?)
+  end
+
+  def inner_instance_sizeof_type(type : Type) : Int32
+    @program.instance_size_of(type.sizeof_type).to_i32
+  end
+
+  def inner_instance_sizeof_type(type : Nil) : Int32
+    0
   end
 
   def offset_of(type : Type, index : Int32) : Int32
diff --git a/src/compiler/crystal/tools/doc/html/type.html b/src/compiler/crystal/tools/doc/html/type.html
index cd8115e74f5c..10c7e51fedd3 100644
--- a/src/compiler/crystal/tools/doc/html/type.html
+++ b/src/compiler/crystal/tools/doc/html/type.html
@@ -95,8 +95,8 @@ <h2>
 
 <%= MethodSummaryTemplate.new("Constructors", type.constructors) %>
 <%= MethodSummaryTemplate.new(type.program? ? "Method Summary" : "Class Method Summary", type.class_methods) %>
-<%= MethodSummaryTemplate.new("Instance Method Summary", type.instance_methods) %>
 <%= MethodSummaryTemplate.new("Macro Summary", type.macros) %>
+<%= MethodSummaryTemplate.new("Instance Method Summary", type.instance_methods) %>
 
 <div class="methods-inherited">
   <% type.ancestors.each do |ancestor| %>
@@ -109,8 +109,8 @@ <h2>
 
 <%= MethodDetailTemplate.new("Constructor Detail", type.constructors) %>
 <%= MethodDetailTemplate.new(type.program? ? "Method Detail" : "Class Method Detail", type.class_methods) %>
-<%= MethodDetailTemplate.new("Instance Method Detail", type.instance_methods) %>
 <%= MethodDetailTemplate.new("Macro Detail", type.macros) %>
+<%= MethodDetailTemplate.new("Instance Method Detail", type.instance_methods) %>
 </div>
 
 </body>
diff --git a/src/compiler/crystal/types.cr b/src/compiler/crystal/types.cr
index 7d4bc9795a7f..ad9f3d391fa6 100644
--- a/src/compiler/crystal/types.cr
+++ b/src/compiler/crystal/types.cr
@@ -2700,7 +2700,7 @@ module Crystal
     end
 
     delegate remove_typedef, pointer?, defs,
-      macros, reference_like?, parents, to: typedef
+      macros, reference_like?, parents, lookup_instance_var, to: typedef
 
     def remove_indirection
       self
diff --git a/src/crystal/system/unix/file.cr b/src/crystal/system/unix/file.cr
index 665a61b22493..ca04693d0b1a 100644
--- a/src/crystal/system/unix/file.cr
+++ b/src/crystal/system/unix/file.cr
@@ -239,7 +239,7 @@ module Crystal::System::File
         sleep 0.1
       end
     else
-      flock(op) || raise IO::Error.from_errno("Error applying file lock: file is already locked")
+      flock(op) || raise IO::Error.from_errno("Error applying file lock: file is already locked", target: self)
     end
   end
 
@@ -251,7 +251,7 @@ module Crystal::System::File
       if errno.in?(Errno::EAGAIN, Errno::EWOULDBLOCK)
         false
       else
-        raise IO::Error.from_os_error("Error applying or removing file lock", errno)
+        raise IO::Error.from_os_error("Error applying or removing file lock", errno, target: self)
       end
     end
   end
@@ -269,7 +269,7 @@ module Crystal::System::File
       end
 
     if ret != 0
-      raise IO::Error.from_errno("Error syncing file")
+      raise IO::Error.from_errno("Error syncing file", target: self)
     end
   end
 end
diff --git a/src/crystal/system/unix/file_descriptor.cr b/src/crystal/system/unix/file_descriptor.cr
index d77708f314bb..d3995c205c3e 100644
--- a/src/crystal/system/unix/file_descriptor.cr
+++ b/src/crystal/system/unix/file_descriptor.cr
@@ -15,7 +15,7 @@ module Crystal::System::FileDescriptor
     evented_read(slice, "Error reading file") do
       LibC.read(fd, slice, slice.size).tap do |return_code|
         if return_code == -1 && Errno.value == Errno::EBADF
-          raise IO::Error.new "File not open for reading"
+          raise IO::Error.new "File not open for reading", target: self
         end
       end
     end
@@ -25,7 +25,7 @@ module Crystal::System::FileDescriptor
     evented_write(slice, "Error writing file") do |slice|
       LibC.write(fd, slice, slice.size).tap do |return_code|
         if return_code == -1 && Errno.value == Errno::EBADF
-          raise IO::Error.new "File not open for writing"
+          raise IO::Error.new "File not open for writing", target: self
         end
       end
     end
@@ -90,13 +90,13 @@ module Crystal::System::FileDescriptor
     seek_value = LibC.lseek(fd, offset, whence)
 
     if seek_value == -1
-      raise IO::Error.from_errno "Unable to seek"
+      raise IO::Error.from_errno "Unable to seek", target: self
     end
   end
 
   private def system_pos
     pos = LibC.lseek(fd, 0, IO::Seek::Current).to_i64
-    raise IO::Error.from_errno "Unable to tell" if pos == -1
+    raise IO::Error.from_errno("Unable to tell", target: self) if pos == -1
     pos
   end
 
@@ -147,7 +147,7 @@ module Crystal::System::FileDescriptor
       when Errno::EINTR, Errno::EINPROGRESS
         # ignore
       else
-        raise IO::Error.from_errno("Error closing file")
+        raise IO::Error.from_errno("Error closing file", target: self)
       end
     end
   end
diff --git a/src/crystal/system/win32/file.cr b/src/crystal/system/win32/file.cr
index 4fceee02c6d4..43b2dd8142ec 100644
--- a/src/crystal/system/win32/file.cr
+++ b/src/crystal/system/win32/file.cr
@@ -493,7 +493,7 @@ module Crystal::System::File
       if winerror == WinError::ERROR_LOCK_VIOLATION
         false
       else
-        raise IO::Error.from_os_error("LockFileEx", winerror)
+        raise IO::Error.from_os_error("LockFileEx", winerror, target: self)
       end
     end
   end
@@ -509,7 +509,7 @@ module Crystal::System::File
 
   private def system_fsync(flush_metadata = true) : Nil
     if LibC._commit(fd) != 0
-      raise IO::Error.from_errno("Error syncing file")
+      raise IO::Error.from_errno("Error syncing file", target: self)
     end
   end
 end
diff --git a/src/crystal/system/win32/file_descriptor.cr b/src/crystal/system/win32/file_descriptor.cr
index 84cfe12c6650..6e4f42d46b17 100644
--- a/src/crystal/system/win32/file_descriptor.cr
+++ b/src/crystal/system/win32/file_descriptor.cr
@@ -15,9 +15,9 @@ module Crystal::System::FileDescriptor
       bytes_read = LibC._read(fd, slice, slice.size)
       if bytes_read == -1
         if Errno.value == Errno::EBADF
-          raise IO::Error.new "File not open for reading"
+          raise IO::Error.new "File not open for reading", target: self
         else
-          raise IO::Error.from_errno("Error reading file")
+          raise IO::Error.from_errno("Error reading file", target: self)
         end
       end
       bytes_read
@@ -36,9 +36,9 @@ module Crystal::System::FileDescriptor
         bytes_written = LibC._write(fd, slice, slice.size)
         if bytes_written == -1
           if Errno.value == Errno::EBADF
-            raise IO::Error.new "File not open for writing"
+            raise IO::Error.new "File not open for writing", target: self
           else
-            raise IO::Error.from_errno("Error writing file")
+            raise IO::Error.from_errno("Error writing file", target: self)
           end
         end
       else
@@ -106,7 +106,7 @@ module Crystal::System::FileDescriptor
 
       if file_type == LibC::FILE_TYPE_UNKNOWN
         error = WinError.value
-        raise IO::Error.from_os_error("Unable to get info", error) unless error == WinError::ERROR_SUCCESS
+        raise IO::Error.from_os_error("Unable to get info", error, target: self) unless error == WinError::ERROR_SUCCESS
       end
     end
 
@@ -129,13 +129,13 @@ module Crystal::System::FileDescriptor
     seek_value = LibC._lseeki64(fd, offset, whence)
 
     if seek_value == -1
-      raise IO::Error.from_errno "Unable to seek"
+      raise IO::Error.from_errno "Unable to seek", target: self
     end
   end
 
   private def system_pos
     pos = LibC._lseeki64(fd, 0, IO::Seek::Current)
-    raise IO::Error.from_errno "Unable to tell" if pos == -1
+    raise IO::Error.from_errno("Unable to tell", target: self) if pos == -1
     pos
   end
 
@@ -165,7 +165,7 @@ module Crystal::System::FileDescriptor
       when Errno::EINTR
         # ignore
       else
-        raise IO::Error.from_errno("Error closing file")
+        raise IO::Error.from_errno("Error closing file", target: self)
       end
     end
   end
@@ -204,7 +204,7 @@ module Crystal::System::FileDescriptor
     if LibC.ReadFile(handle, buffer, buffer.size, out bytes_read, pointerof(overlapped)) == 0
       error = WinError.value
       return 0_i64 if error == WinError::ERROR_HANDLE_EOF
-      raise IO::Error.from_os_error "Error reading file", error
+      raise IO::Error.from_os_error "Error reading file", error, target: self
     end
 
     bytes_read.to_i64
diff --git a/src/file/error.cr b/src/file/error.cr
index 79a0ec5978dc..355496488bc4 100644
--- a/src/file/error.cr
+++ b/src/file/error.cr
@@ -2,9 +2,12 @@ class File < IO::FileDescriptor
 end
 
 class File::Error < IO::Error
-  getter file : String
   getter other : String?
 
+  def file : String
+    target.not_nil!
+  end
+
   private def self.new_from_os_error(message, os_error, **opts)
     case os_error
     when Errno::ENOENT, WinError::ERROR_FILE_NOT_FOUND, WinError::ERROR_PATH_NOT_FOUND
@@ -20,6 +23,10 @@ class File::Error < IO::Error
     end
   end
 
+  def initialize(message, *, file : String | Path, @other : String? = nil)
+    super message, target: file
+  end
+
   protected def self.build_message(message, *, file : String) : String
     "#{message}: '#{file.inspect_unquoted}'"
   end
@@ -38,11 +45,6 @@ class File::Error < IO::Error
       end
     end
   {% end %}
-
-  def initialize(message, *, file : String | Path, @other : String? = nil)
-    @file = file.to_s
-    super message
-  end
 end
 
 class File::NotFoundError < File::Error
diff --git a/src/io/error.cr b/src/io/error.cr
index b611dc523818..4c6d30952f13 100644
--- a/src/io/error.cr
+++ b/src/io/error.cr
@@ -1,6 +1,26 @@
 class IO
   class Error < Exception
     include SystemError
+
+    getter target : String?
+
+    protected def self.build_message(message, *, target : File) : String
+      build_message(message, target: target.path)
+    end
+
+    protected def self.build_message(message, *, target : Nil) : String
+      message
+    end
+
+    protected def self.build_message(message, *, target) : String
+      "#{message} (#{target})"
+    end
+
+    def initialize(message : String? = nil, *, target = nil)
+      @target = target.try(&.to_s)
+
+      super message
+    end
   end
 
   # Raised when an `IO` operation times out.
diff --git a/src/io/evented.cr b/src/io/evented.cr
index c490f3b5939f..191f136466a1 100644
--- a/src/io/evented.cr
+++ b/src/io/evented.cr
@@ -58,7 +58,7 @@ module IO::Evented
       if Errno.value == Errno::EAGAIN
         wait_readable
       else
-        raise IO::Error.from_errno(errno_msg)
+        raise IO::Error.from_errno(errno_msg, target: self)
       end
     end
   ensure
@@ -79,7 +79,7 @@ module IO::Evented
           if Errno.value == Errno::EAGAIN
             wait_writable
           else
-            raise IO::Error.from_errno(errno_msg)
+            raise IO::Error.from_errno(errno_msg, target: self)
           end
         end
       end
diff --git a/src/io/overlapped.cr b/src/io/overlapped.cr
index d4b9f5f0cb6f..d7ed8aa516ec 100644
--- a/src/io/overlapped.cr
+++ b/src/io/overlapped.cr
@@ -211,9 +211,9 @@ module IO::Overlapped
         when .error_io_pending?
           # the operation is running asynchronously; do nothing
         when .error_access_denied?
-          raise IO::Error.new "File not open for #{writing ? "writing" : "reading"}"
+          raise IO::Error.new "File not open for #{writing ? "writing" : "reading"}", target: self
         else
-          raise IO::Error.from_os_error(method, error)
+          raise IO::Error.from_os_error(method, error, target: self)
         end
       else
         operation.synchronous = true
@@ -245,7 +245,7 @@ module IO::Overlapped
         when .wsa_io_pending?
           # the operation is running asynchronously; do nothing
         else
-          raise IO::Error.from_os_error(method, error)
+          raise IO::Error.from_os_error(method, error, target: self)
         end
       else
         operation.synchronous = true
diff --git a/src/string.cr b/src/string.cr
index 3c378bd1d455..98b7ec3884fd 100644
--- a/src/string.cr
+++ b/src/string.cr
@@ -3416,9 +3416,19 @@ class String
     self.match(search, offset, options: options).try &.begin
   end
 
-  # :ditto:
+  # Returns the index of the _first_ occurrence of *search* in the string. If *offset* is present,
+  # it defines the position to start the search.
   #
   # Raises `Enumerable::NotFoundError` if *search* does not occur in `self`.
+  #
+  # ```
+  # "Hello, World".index!('o')    # => 4
+  # "Hello, World".index!('Z')    # raises Enumerable::NotFoundError
+  # "Hello, World".index!("o", 5) # => 8
+  # "Hello, World".index!("H", 2) # raises Enumerable::NotFoundError
+  # "Hello, World".index!(/[ ]+/) # => 6
+  # "Hello, World".index!(/\d+/)  # raises Enumerable::NotFoundError
+  # ```
   def index!(search, offset = 0) : Int32
     index(search, offset) || raise Enumerable::NotFoundError.new
   end
@@ -4687,6 +4697,48 @@ class String
     regex.matches? self, pos, options: options
   end
 
+  # Matches the regular expression *regex* against the entire string and returns
+  # the resulting `MatchData`.
+  # It also updates `$~` with the result.
+  #
+  # ```
+  # "foo".match_full(/foo/)  # => Regex::MatchData("foo")
+  # $~                       # => Regex::MatchData("foo")
+  # "fooo".match_full(/foo/) # => nil
+  # $~                       # raises Exception
+  # ```
+  def match_full(regex : Regex) : Regex::MatchData?
+    match(regex, options: Regex::MatchOptions::ANCHORED | Regex::MatchOptions::ENDANCHORED)
+  end
+
+  # Matches the regular expression *regex* against the entire string and returns
+  # the resulting `MatchData`.
+  # It also updates `$~` with the result.
+  # Raises `Regex::Error` if there are no matches.
+  #
+  # ```
+  # "foo".match_full!(/foo/)  # => Regex::MatchData("foo")
+  # $~                        # => Regex::MatchData("foo")
+  # "fooo".match_full!(/foo/) # Regex::Error
+  # $~                        # raises Exception
+  # ```
+  def match_full!(regex : Regex) : Regex::MatchData?
+    match!(regex, options: Regex::MatchOptions::ANCHORED | Regex::MatchOptions::ENDANCHORED)
+  end
+
+  # Returns `true` if the regular expression *regex* matches this string entirely.
+  #
+  # ```
+  # "foo".matches_full?(/foo/)  # => true
+  # "fooo".matches_full?(/foo/) # => false
+  #
+  # # `$~` is not set even if last match succeeds.
+  # $~ # raises Exception
+  # ```
+  def matches_full?(regex : Regex) : Bool
+    matches?(regex, options: Regex::MatchOptions::ANCHORED | Regex::MatchOptions::ENDANCHORED)
+  end
+
   # Searches the string for instances of *pattern*,
   # yielding a `Regex::MatchData` for each match.
   def scan(pattern : Regex, *, options : Regex::MatchOptions = Regex::MatchOptions::None, &) : self