patch 9.0.2104: wast filetype should be replaced by wat filetype

Problem:  wast filetype should be replaced by wat filetype
Solution: start using the official wat filetype name

runtime: rename `wast` filetype to `wat` (Wasm text format)

The problem is the name of the current filetype wast. When the plugin
was initially created, the file extension for Wasm text format was not
fixed and .wast was more popular.

However, recently .wat became the official file extension for
WebAssembly text (WAT) format and .wast is now a file extension for the
unofficial WAST format, which is a superset of .wat for the convenience
to describe the Wasm specification conformance tests.

https://webassembly.js.org/docs/contrib-wat-vs-wast.html

However for now, let's keep using the `wat` filetype even for the .wast
extension, so that we at least do not lose the filetype settings and
syntax highlighting. This can be adjusted later, if it turns out to have
a separate need for.

closes: #13533

Signed-off-by: rhysd <lin90162@yahoo.co.jp>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/syntax/wat.vim b/runtime/syntax/wat.vim
new file mode 100644
index 0000000..a6b926b
--- /dev/null
+++ b/runtime/syntax/wat.vim
@@ -0,0 +1,97 @@
+" Vim syntax file
+" Language:     WebAssembly
+" Maintainer:   rhysd <lin90162@yahoo.co.jp>
+" Last Change:  Nov 14, 2023
+" For bugs, patches and license go to https://github.com/rhysd/vim-wasm
+
+if exists("b:current_syntax")
+    finish
+endif
+
+let s:cpo_save = &cpo
+set cpo&vim
+
+syn cluster watNotTop contains=watModule,watInstWithType,watInstGetSet,watInstGeneral,watParamInst,watControlInst,watSimdInst,watString,watNamedVar,watUnnamedVar,watFloat,watNumber,watComment,watList,watType
+
+" Instructions
+" https://webassembly.github.io/spec/core/text/instructions.html
+" Note: memarg (align=,offset=) can be added to memory instructions
+syn match   watInstWithType  "\%((\s*\)\@<=\<\%(i32\|i64\|f32\|f64\|memory\)\.[[:alnum:]_]\+\%(/\%(i32\|i64\|f32\|f64\)\)\=\>\%(\s\+\%(align\|offset\)=\)\=" contained display
+syn match   watInstGeneral   "\%((\s*\)\@<=\<[[:alnum:]_]\+\>" contained display
+syn match   watInstGetSet    "\%((\s*\)\@<=\<\%(local\|global\)\.\%(get\|set\)\>" contained display
+" https://webassembly.github.io/spec/core/text/instructions.html#control-instructions
+syn match   watControlInst   "\%((\s*\)\@<=\<\%(block\|end\|loop\|if\|then\|else\|unreachable\|nop\|br\|br_if\|br_table\|return\|call\|call_indirect\)\>" contained display
+" https://webassembly.github.io/spec/core/text/instructions.html#parametric-instructions
+syn match   watParamInst     "\%((\s*\)\@<=\<\%(drop\|select\)\>" contained display
+" SIMD instructions
+" https://webassembly.github.io/simd/core/text/instructions.html#simd-instructions
+syn match   watSimdInst      "\<\%(v128\|i8x16\|i16x8\|i32x4\|i64x2\|f32x4\|f64x2)\)\.[[:alnum:]_]\+\%(\s\+\%(i8x16\|i16x8\|i32x4\|i64x2\|f32x4\|f64x2\)\)\=\>" contained display
+
+" Identifiers
+" https://webassembly.github.io/spec/core/text/values.html#text-id
+syn match   watNamedVar      "$\+[[:alnum:]!#$%&'∗./:=><?@\\^_`~+-]*" contained contains=watEscapeUtf8
+syn match   watUnnamedVar    "$\+\d\+[[:alnum:]!#$%&'∗./:=><?@\\^_`~+-]\@!" contained display
+" Presuming the source text is itself encoded correctly, strings that do not
+" contain any uses of hexadecimal byte escapes are always valid names.
+" https://webassembly.github.io/spec/core/text/values.html#names
+syn match   watEscapedUtf8   "\\\x\{1,6}" contained containedin=watNamedVar display
+
+" String literals
+" https://webassembly.github.io/spec/core/text/values.html#strings
+syn region  watString        start=+"+ skip=+\\\\\|\\"+ end=+"+ contained contains=watStringSpecial
+syn match   watStringSpecial "\\\x\x\|\\[tnr'\\\"]\|\\u\x\+" contained containedin=watString display
+
+" Float literals
+" https://webassembly.github.io/spec/core/text/values.html#floating-point
+syn match   watFloat         "\<-\=\d\%(_\=\d\)*\%(\.\d\%(_\=\d\)*\)\=\%([eE][-+]\=\d\%(_\=\d\)*\)\=" display contained
+syn match   watFloat         "\<-\=0x\x\%(_\=\x\)*\%(\.\x\%(_\=\x\)*\)\=\%([pP][-+]\=\d\%(_\=\d\)*\)\=" display contained
+syn keyword watFloat         inf nan contained
+syn match   watFloat         "nan:0x\x\%(_\=\x\)*" display contained
+
+" Integer literals
+" https://webassembly.github.io/spec/core/text/values.html#integers
+syn match   watNumber        "\<-\=\d\%(_\=\d\)*\>" display contained
+syn match   watNumber        "\<-\=0x\x\%(_\=\x\)*\>" display contained
+
+" Comments
+" https://webassembly.github.io/spec/core/text/lexical.html#comments
+syn region  watComment       start=";;" end="$"
+syn region  watComment       start="(;;\@!" end=";)"
+
+syn region  watList          matchgroup=watListDelimiter start="(;\@!" matchgroup=watListDelimiter end=";\@<!)" contains=@watNotTop
+
+" Types
+" https://webassembly.github.io/spec/core/text/types.html
+" Note: `mut` was changed to `const`/`var` at Wasm 2.0
+syn keyword watType          i64 i32 f64 f32 param result funcref func externref extern mut v128 const var contained
+syn match   watType          "\%((\_s*\)\@<=func\%(\_s*[()]\)\@=" display contained
+
+" Modules
+" https://webassembly.github.io/spec/core/text/modules.html
+syn keyword watModule        module type export import table memory global data elem contained
+syn match   watModule        "\%((\_s*\)\@<=func\%(\_s\+\$\)\@=" display contained
+
+syn sync maxlines=100
+
+hi def link watModule        PreProc
+hi def link watListDelimiter Delimiter
+hi def link watInstWithType  Operator
+hi def link watInstGetSet    Operator
+hi def link watInstGeneral   Operator
+hi def link watControlInst   Statement
+hi def link watSimdInst      Operator
+hi def link watParamInst     Conditional
+hi def link watString        String
+hi def link watStringSpecial Special
+hi def link watNamedVar      Identifier
+hi def link watUnnamedVar    PreProc
+hi def link watFloat         Float
+hi def link watNumber        Number
+hi def link watComment       Comment
+hi def link watType          Type
+hi def link watEscapedUtf8   Special
+
+let b:current_syntax = "wat"
+
+let &cpo = s:cpo_save
+unlet s:cpo_save