Improve go highlighting for type assertions

after/syntax/go.vim

@@ -20,9 +20,9 @@ if g:go_highlight_types != 0
   syn clear goTypeName
   syn clear goDeclType
 
-  syn cluster validTypeContains          contains=goComment,goNewDeclType,goDeclTypeField,goDeclTypeW,goDeclTypeFieldSlice,goDeclTypeFieldPointerOp,goString,goRawString,OperatorChars,goContainer
-  syn cluster validStructContains        contains=goComment,goNewDeclType,goDeclTypeField,goDeclTypeW,goString,goRawString,OperatorChars,goContainer
-  syn cluster validInterfaceContains     contains=goComment,goFunction,OperatorChars,goContainer,goType,goNestedInterfaceType
+  syn cluster validTypeContains          contains=goComment,goNewDeclType,goDeclTypeField
+  syn cluster validStructContains        contains=goComment,goNewDeclType,goDeclTypeField,goString,goRawString
+  syn cluster validInterfaceContains     contains=goComment,goFunction,goNestedInterfaceType
 
   syn match goTypeDecl                   /\<type\>/ nextgroup=goNewDeclType,goTypeRegion skipwhite skipnl
   syn region goTypeRegion                matchgroup=goContainer start=/(/ end=/)/ contains=@validTypeContains fold contained
@@ -30,27 +30,38 @@ if g:go_highlight_types != 0
   syn region goDeclInterfaceRegion       matchgroup=goContainer start=/{/ end=/}/ contains=@validInterfaceContains fold contained
   syn match goNestedInterfaceType        /\w\+/ contained
 
-  " I think I hate this
-  syn cluster goDeclTypeContains         contains=goDeclTypeNS,goDeclTypeType,goDeclTypeMapType,goDeclTypeMap,ContainerChars,OperatorChars,goDeclaration,goDeclStruct,goDeclInterface
+  " I think I hate this and could be better
+  syn cluster goDeclTypeContains         contains=goDeclTypeNS,goDeclTypeType,goMapKeyRegion,ContainerChars,OperatorChars,goDeclaration,goDeclStruct,goDeclInterface,goExtraType
   " Match \w+\.\w+ but only highlight lone \w+ or (?>\.)\w+
   syn match goDeclTypeW                  /\(\[.*\]\|\*\)*\(\w\+\.\)\?\w\+\(\[.*\]\S\+\)\?/ contains=@goDeclTypeContains skipwhite contained
-  " this is actually horribly broken for nested maps but appears to work.. 🤷
-  syn match goDeclTypeType               /\w\+/ contains=@goNumber nextgroup=goDeclTypeMap skipwhite contained
-  syn region goDeclTypeMap               matchgroup=goContainer start=/\[/ end=/\]/ contains=goDeclTypeW,ContainerChars nextgroup=goDeclTypeW skipwhite contained
+  " this is actually horribly broken for nested maps but appears to work..
+  " NOTE: I think fixing goDeclTypeW would fix mismatched brackets
+  syn match goDeclTypeType               /\w\+/ contains=@goNumber nextgroup=goMapKeyRegion skipwhite contained
+  syn region goMapKeyRegion              matchgroup=goContainer start=/\[/ end=/\]/ contains=goDeclTypeW,ContainerChars nextgroup=goDeclTypeW skipwhite contained
   syn match goDeclTypeNS                 /\w\+\(\.\)\@1=/ skipwhite contained
 
+  syn keyword goMapType                  map nextgroup=goMapKeyRegion
+
   syn match goDeclTypeFieldPointerOp     /\*/ nextgroup=goDeclTypeFieldPointerOp,goDeclTypeFieldSlice,goDeclTypeW,goDeclStruct,goDeclInterface skipwhite contained
-  syn region goDeclTypeFieldSlice        matchgroup=goContainer start=/\[/ end=/\]/ contains=goDecimalInt,goHexadecimalInt,goOctalInt nextgroup=goDeclTypeFieldPointerOp,goDeclTypeFieldSlice,goDeclTypeW,goDeclStruct,goDeclInterface skipwhite keepend contained
+  syn region goDeclTypeFieldSlice        matchgroup=goContainer start=/\[/ end=/\]/ nextgroup=goDeclTypeFieldPointerOp,goDeclTypeFieldSlice,goDeclTypeW,goDeclStruct,goDeclInterface skipwhite transparent contained
 
   syn match goDeclTypeField              /\w\+/ nextgroup=goDeclTypeW skipwhite contained
 
+  " This is important in order to differentiate "field type" from "field struct"
+  " and "field interface"
   syn match goNewDeclType                /\w\+\(\s\([*\[\] ]\)*\<\(struct\|interface\)\>\)\@=/ nextgroup=goDeclTypeFieldPointerOp,goDeclTypeFieldSlice,goDeclStruct,goDeclInterface skipwhite contained
   syn match goDeclStruct                 /\<struct\>/ nextgroup=goDeclStructRegion skipwhite skipnl
   syn match goDeclInterface              /\<interface\>/ nextgroup=goDeclInterfaceRegion skipwhite skipnl
 
   syn match goVarVar                     /[^, ]\+/ nextgroup=goVarSep,goDeclTypeW skipwhite contained
   syn match goVarSep                     /,/ nextgroup=goVarVar skipwhite contained
-  syn keyword goVarDecl                  var nextgroup=goVarVar skipwhite
+  " TODO:
+  syn region goVarRegion                 matchgroup=goContainer start=/(/ end=/)/ transparent contained
+  syn keyword goVarDecl                  var nextgroup=goVarVar,goVarRegion skipwhite
+
+  " NOTE: incomplete, but good enough for now
+  syn region goTypeAssertionRegion       matchgroup=goContainer start=/(/ end=/)/ contains=goDeclTypeW skipwhite contained
+  syn match goTypeAssertionOp            /\.\((\)\@=/ nextgroup=goTypeAssertionRegion skipwhite
 endif
 
 if !exists("g:go_highlight_functions")
@@ -61,23 +72,27 @@ if g:go_highlight_functions != 0
   syn clear goFunction
   syn clear goReceiverType
 
-  syn match goFunctionCall          /\(\.\)\@1<!\w\+\((\)\@1=/
+  syn match goFunctionCall          /\(\.\)\@1<!\w\+\((\)\@1=/ nextgroup=goFuncMethCallRegion
 
   " This works but much like everything else, it is quite fragile. It doesn't
   " handle inline interfaces or structs (but should it, really?). Though, that
   " is probably more because of the terrible goDeclTypeW.. who knows...
   " Whatever.. it seems to fit 98% of my use cases
+  " NOTE: I think fixing goDeclTypeW would fix inlined interface/structs
   syn match listOfTypes             /\(\S\+\ze[,)]\)\+/ contains=goDeclTypeW,ContainerChars contained
-  syn match listOfVars              /\(, \|(\)\@<=\w\+\(\(, \w\+\)*, \w\+ \)\@=/ contained
+  syn match listOfVars              /\([,(]\s*\)\@<=\w\+\(\(, \w\+\)*, \w\+ \)\@=/ contained
 
+  " TODO: change to "does not start with , or {"
   syn match goFunctionReturn        /[^{, ]\+/ contains=goDeclaration,goDeclTypeW skipwhite contained
+  " NOTE: I think fixing goDeclTypeW would the need for "keepend extend"
+  " Also transparent might help... (use only contains=listOfTypes,listOfVars ?)
   syn region goFunctionParamRegion  matchgroup=goContainer start=/(/ end=/)/ contains=goDeclaration,listOfTypes,listOfVars,ContainerChars,OperatorChars nextgroup=goFunctionReturn,goFunctionReturnRegion skipwhite keepend extend contained
   syn region goFunctionReturnRegion matchgroup=goContainer start=/(/ end=/)/ contains=goDeclaration,listOfTypes,listOfVars,ContainerChars,OperatorChars skipwhite keepend extend contained
   syn match goFunction              /\w\+\((\)\@1=/ nextgroup=goFunctionParamRegion skipwhite contained
 
   syn match goDeclaration           /\<func\>/ nextgroup=goReceiverRegion,goFunction,goFunctionParamRegion skipwhite skipnl
   " Use the space between func and ( to determine if the next group is a
-  " receiver or an inlined function
+  " receiver or an inlined function (which matches gofmt)
   syn region goReceiverRegion       matchgroup=goContainer start=/ (/ end=/)/ contains=goReceiver nextgroup=goFunction skipwhite contained
   syn match goReceiver              /\(\w\|[ *]\)\+/ contains=goReceiverVar,goPointerOperator skipwhite skipnl contained
   syn match goReceiverVar           /\w\+/ nextgroup=goPointerOperator,goDeclTypeW skipwhite skipnl contained
@@ -89,17 +104,21 @@ if !exists("g:go_highlight_methods")
 endif
 if g:go_highlight_methods != 0
   syn clear goMethodCall
-  syn match goMethodCall            /\(\.\)\@1<=\w\+\((\)\@1=/
+  syn match goMethodCall            /\(\.\)\@1<=\w\+\((\)\@1=/ nextgroup=goFuncMethCallRegion
 endif
 
+syn region goFuncMethCallRegion   matchgroup=goContainer start=/(/ end=/)/ contained transparent
+
 syn match goLiteralStructField /\w\+\ze:[^=]/
 
 " Order is important, so redefine
-syn match goBuiltins /\<\v(append|cap|close|complex|copy|delete|imag|len)\ze\(/
-syn match goBuiltins /\<\v(make|new|panic|print|println|real|recover)\ze\(/
+syn match goBuiltins /\<\(append\|cap\|close\|complex\|copy\|delete\|imag\|len\)\((\)\@=/ nextgroup=goBuiltinRegion
+syn match goBuiltins /\<\(make\|new\|panic\|print\|println\|real\|recover\)\((\)\@=/ nextgroup=goBuiltinRegion
+syn region goBuiltinRegion matchgroup=goContainer start=/(/ end=/)/ transparent contained
 
 hi link goPointerOperator        Operator
 hi link goDeclTypeFieldPointerOp Operator
+hi link goTypeAssertionOp        Operator
 
 hi link goTypeConstructor        Type
 hi link goTypeOpen               goContainer