diff --git a/packages/DomainCode-Parser/DCBlock.class.st b/packages/DomainCode-Parser/DCBlock.class.st
index afc3400..cea1785 100644
--- a/packages/DomainCode-Parser/DCBlock.class.st
+++ b/packages/DomainCode-Parser/DCBlock.class.st
@@ -257,7 +257,7 @@ DCBlock class >> smalltalkCollapseBlocks [
 	^ {
 		[:x | x language = SBTSSmalltalk].
 		[:x | x type = #block].
-		[:x | x sourceString size > 400].
+		[:x | x sourceString size > 3000].
 		[:x | x installPassiveReplacement: DCCollapsed new]}
 ]
 
@@ -271,6 +271,16 @@ DCBlock class >> smalltalkCollapseBlocksOnDoubleClick [
 		[:x | x installPassiveReplacement: DCCollapsed new]}
 ]
 
+{ #category : #'smalltalk - helpers' }
+DCBlock class >> smalltalkCreateClassFor: aBlock [
+
+	aBlock sandblockEditor do: (SBStCreateClassCommand new
+		name: aBlock contents;
+		source: aBlock;
+		editor: aBlock sandblockEditor;
+		artefact: aBlock containingArtefact)
+]
+
 { #category : #smalltalk }
 DCBlock class >> smalltalkCreateNewMethod [
 	<query: #shortcut>
@@ -323,6 +333,78 @@ DCBlock class >> smalltalkDeclaration [
 			{#args. id. decl}]}
 ]
 
+{ #category : #'smalltalk - helpers' }
+DCBlock class >> smalltalkDeclareBlockLocal: aBlock [
+
+	| block decl |
+	decl := DCBlock new
+		type: #identifier;
+		addMorphBack: (DCText new contents: aBlock contents).
+	block := aBlock orAnyParent: {#block. #method}.
+	block childSandblocks
+		detect: [:b | b type = #temporaries]
+		ifFound: [:temporaries |
+			aBlock sandblockEditor do: (SBInsertCommand new
+				morph: decl;
+				container: temporaries;
+				index: temporaries submorphCount)]
+		ifNone: [ | index |
+			index := block children findFirst: [:s | s treeLabel = '|'].
+			aBlock sandblockEditor do: (SBInsertCommand new
+				morph: (DCBlock new
+					type: #temporaries;
+					addMorphBack: (DCText new contents: '|');
+					addMorphBack: decl;
+					addMorphBack: (DCText new contents: '|'));
+				index: (index = 0 ifTrue: [2] ifFalse: [index + 1]);
+				container: block)]
+]
+
+{ #category : #'smalltalk - helpers' }
+DCBlock class >> smalltalkDeclareClassVariable: aBlock [
+
+	aBlock sandblockEditor do: (SBStDeclareClassVarCommand new
+		class: aBlock containingArtefact methodClass theNonMetaClass;
+		name: aBlock contents;
+		source: aBlock)
+]
+
+{ #category : #'smalltalk - helpers' }
+DCBlock class >> smalltalkDeclareInstanceVariable: aBlock [
+
+	aBlock sandblockEditor do: (SBStDeclareInstVarCommand new
+		class: aBlock containingArtefact methodClass;
+		name: aBlock contents;
+		source: aBlock)
+]
+
+{ #category : #'smalltalk - helpers' }
+DCBlock class >> smalltalkDeclareTemporary: aBlock [
+
+	| block decl |
+	decl := DCBlock new
+		type: #identifier;
+		addMorphBack: (DCText new contents: aBlock contents).
+	block := aBlock orAnyParent: {#method}.
+	block childSandblocks
+		detect: [:b | b type = #temporaries]
+		ifFound: [:temporaries |
+			aBlock sandblockEditor do: (SBInsertCommand new
+				morph: decl;
+				container: temporaries;
+				index: temporaries submorphCount)]
+		ifNone: [ | index |
+			index := block children findFirst: [:s | s treeLabel = '|'].
+			aBlock sandblockEditor do: (SBInsertCommand new
+				morph: (DCBlock new
+					type: #temporaries;
+					addMorphBack: (DCText new contents: '|');
+					addMorphBack: decl;
+					addMorphBack: (DCText new contents: '|'));
+				index: (index = 0 ifTrue: [2] ifFalse: [index + 1]);
+				container: block)]
+]
+
 { #category : #smalltalk }
 DCBlock class >> smalltalkFlagMarker [
 	<query: #always>
@@ -398,13 +480,11 @@ DCBlock class >> smalltalkInsertArg [
 			#(#First #Second #Third #Fourth #Fifith) withIndexDo: [:name :index |
 				x registerShortcut: #use, name, #Argument do: [
 					{
-						[:block | | id |
-							id := DCQuery
-								script: {self smalltalkMethodArguments. [:args | (args at: index) contents]}
-								with: block.
-							(block type = #identifier or: [block sandblockEditor mode = #command])
-								ifTrue: [block replaceWith: id, ' ']
-								ifFalse: [block insert: id, ' ']]}]]]}
+						[:block |
+							(DCQuery script: {self smalltalkMethodArguments. [:args | (args at: index) contents]} with: block) ifNotNil: [:id |
+								(block type = #identifier or: [block sandblockEditor mode = #command])
+									ifTrue: [block replaceWith: id, ' ']
+									ifFalse: [block insert: id, ' ']]]}]]]}
 ]
 
 { #category : #smalltalk }
@@ -448,13 +528,19 @@ DCBlock class >> smalltalkMessageSendAutoCompletion [
 
 	^ {
 		[:x | x isSelected].
+		[:x | "only autocomplete for the first message part (just after receiver)"
+		x siblingIndex = 2].
 		[:x | (DCQuery script: self smalltalkMessageSendSelector with: x) ifNotNil: [:res | res, {x}]].
 		[:selector :message :part |
 			part addSuggestions: ((self sortedSuggestions: Symbol allSymbols for: selector addAll: false max: 10) collect: [:sel |
 				DCSuggestionItem new
 					selector: sel label: 'send' source: ((sel allSatisfy: #isSpecial) ifTrue: [sel, ' __sb'] ifFalse: [
 						(sel includes: $:)
-							ifTrue: [((sel splitBy: ':') allButLast collect: [:p | p, ': __sb']) joinSeparatedBy: ' ']
+							ifTrue: [
+								((sel splitBy: ':') allButLast collectWithIndex: [:p :index |
+									p, ((index = 1 and: [part nextBlock ifNotNil: #isExpression ifNil: [false]])
+										ifTrue: [':']
+										ifFalse: [': __sb'])]) joinSeparatedBy: ' ']
 							ifFalse: [sel]]);
 					completionAction: [:editor |
 						editor selection parent
@@ -492,7 +578,7 @@ DCBlock class >> smalltalkMethodSelector [
 				ifNone: [nil]]}
 ]
 
-{ #category : #nil }
+{ #category : #smalltalk }
 DCBlock class >> smalltalkRunTest [
 	<query: #save>
 
@@ -536,6 +622,25 @@ DCBlock class >> smalltalkSelector [
 				with: x]}
 ]
 
+{ #category : #'smalltalk - helpers' }
+DCBlock class >> smalltalkSelectorWithPlaceholders: aString [
+
+	(aString allSatisfy: #isSpecial) ifTrue: [^ aString, ' __sb'].
+	(aString includes: $:) ifFalse: [^ aString].
+	^ ((aString splitBy: ':') allButLast collect: [:part | part, ': __sb']) joinSeparatedBy: ' '
+]
+
+{ #category : #smalltalk }
+DCBlock class >> smalltalkSymbolAutocompletion [
+	<query: #type>
+
+	^ {
+		[:x | x isSelected].
+		[:x | x language = SBTSSmalltalk].
+		[:x | x type = #symbol].
+		[:x | x addSuggestions: ((self sortedSuggestions: Symbol allSymbols for: x contents allButFirst addAll: false max: 10) collect: [:sel | DCSuggestionItem new selector: sel label: 'symbol' source: sel])]}
+]
+
 { #category : #smalltalk }
 DCBlock class >> smalltalkToggleBoolean [
 	<query: #doubleClick>
@@ -560,29 +665,57 @@ DCBlock class >> smalltalkUndeclaredVariable [
 		[:x |
 			x reportError: (SBErrorDecorator new
 				message: 'undeclared variable';
+				fixActions: (x contents first isUppercase
+					ifTrue: [
+						{
+							SBCodeAction
+								labeled: 'Declare class var'
+								for: x
+								do: [:block | self smalltalkDeclareClassVariable: block].
+							SBCodeAction
+								labeled: 'Create class ', x contents
+								for: x
+								do: [:block | self smalltalkCreateClassFor: block]}]
+					ifFalse: [
+						{
+							SBCodeAction
+								labeled: 'Declare block-local'
+								for: x
+								do: [:block | self smalltalkDeclareBlockLocal: block].
+							SBCodeAction
+								labeled: 'Declare method temporary'
+								for: x
+								do: [:block | self smalltalkDeclareTemporary block].
+							SBCodeAction
+								labeled: 'Declare instance variable'
+								for: x
+								do: [:block | self smalltalkDeclareInstanceVariable: block]}]))]}
+]
+
+{ #category : #smalltalk }
+DCBlock class >> smalltalkUnknownSelector [
+	<query: #type>
+
+	^ {
+		self smalltalkMessageSendSelector.
+		[:selector :message | (Symbol lookup: selector) isNil].
+		[:selector :message |
+			message children second reportError: (SBErrorDecorator new
+				message: 'unknown message';
 				fixActions: {
-					SBCodeAction labeled: 'Declare block-local' for: x do: [:node | | block decl |
-						decl := DCBlock new
-							type: #identifier;
-							addMorphBack: (DCText new contents: node contents).
-						block := node orAnyParent: {#block. #method}.
-						block childSandblocks
-							detect: [:b | b type = #temporaries]
-							ifFound: [:temporaries |
-								node sandblockEditor do: (SBInsertCommand new
-									morph: decl;
-									container: temporaries;
-									index: temporaries submorphCount)]
-							ifNone: [ | index |
-								index := block children findFirst: [:s | s treeLabel = '|'].
-								node sandblockEditor do: (SBInsertCommand new
-									morph: (DCBlock new
-										type: #temporaries;
-										addMorphBack: (DCText new contents: '|');
-										addMorphBack: decl;
-										addMorphBack: (DCText new contents: '|'));
-									index: (index = 0 ifTrue: [2] ifFalse: [index + 1]);
-									container: block)]]})]}
+					SBCodeAction labeled: 'Create method on ...' for: message do: [:node | | method class |
+						class := UIManager default chooseClassOrTrait.
+						class ifNotNil: [
+							self halt.
+							method := DCSmalltalkMethod
+								newWith: (self smalltalkSelectorWithPlaceholders: selector)
+								in: class.
+							node sandblockEditor do: (SBEditorOpenMorphCommand new
+								morph: method;
+								editor: node sandblockEditor;
+								isUnsaved: true;
+								yourself)]].
+					SBCodeAction labeled: 'Confirm selector' for: message do: [:node | node selector asSymbol]})]}
 ]
 
 { #category : #smalltalk }
@@ -638,7 +771,7 @@ DCBlock class >> smalltalkWatch [
 					expr := message children third.
 					{
 						expr type = 'parenthesized_expression'
-							ifTrue: [expr children first]
+							ifTrue: [expr children second]
 							ifFalse: [expr]}]
 				initDo: [:w :expr | w addMorphBack: expr]]}
 ]
@@ -1213,6 +1346,14 @@ DCBlock >> isBlockBody [
 	^ self language ifNotNil: [:l | l blockBodyTypes includes: self type] ifNil: [false]
 ]
 
+{ #category : #'as yet unclassified' }
+DCBlock >> isExpression [
+
+	(self type = #ERROR and: [self submorphCount = 1]) ifTrue: [^ self firstSubmorph isExpression].
+	
+	^ self language expressionTypes anySatisfy: [:type | self language instance grammar is: self type subtypeOf: type]
+]
+
 { #category : #hierarchy }
 DCBlock >> isOrHasParent: aCollectionOrSymbol [
 
@@ -1503,6 +1644,8 @@ DCBlock >> printTreeOn: aStream indent: aNumber [
 { #category : #'as yet unclassified' }
 DCBlock >> queryAll: aString [
 
+	self assert: (aString includes: $@) description: 'query needs a capture (@) to be useful'.
+	
 	^ Array streamContents: [:stream |
 		self allChildrenDo: [:block |
 			block isTSMorph ifTrue: [
diff --git a/packages/DomainCode-Parser/DCEditTest.class.st b/packages/DomainCode-Parser/DCEditTest.class.st
index 8acb875..00a2153 100644
--- a/packages/DomainCode-Parser/DCEditTest.class.st
+++ b/packages/DomainCode-Parser/DCEditTest.class.st
@@ -62,6 +62,44 @@ c.' language: SBTSSmalltalk.
 c .' equals: editor childSandblocks first sourceString
 ]
 
+{ #category : #'as yet unclassified' }
+DCEditTest >> testSmalltalkEditMessageWithAutoCompl [
+
+	| block editor |
+	block := DCSmalltalkMethod newWith: 'a
+
+a with: 3' in: self class.
+	editor := self editorAndWorldFor: block.
+	(block method queryAll: '(keyword) @') first
+		select;
+		clearInput.
+	self type: 'with' in: editor.
+	self tick.
+	editor handle: (SBTest keyboardEvent: Character tab).
+	self assert: 'a
+
+a with: 3' equals: block method sourceString
+]
+
+{ #category : #'as yet unclassified' }
+DCEditTest >> testSmalltalkFillPlaceholderWithArg [
+
+	| block editor |
+	block := DCSmalltalkMethod newWith: 'a: arg
+
+a' in: self class.
+	editor := self editorAndWorldFor: block.
+	block lastDeepChild startInputAtEnd.
+	self type: ' with' in: editor.
+	self tick.
+	editor handle: (SBTest keyboardEvent: Character tab).
+	self tick.
+	editor handle: (SBTest keyboardEvent: $1 shift: false command: true).
+	self assert: 'a: arg
+
+a with: arg' equals: block method sourceString
+]
+
 { #category : #'as yet unclassified' }
 DCEditTest >> testSmalltalkSwapStatementsWithEmpty [
 
diff --git a/packages/DomainCode-Parser/DCJumpPlaceholder.class.st b/packages/DomainCode-Parser/DCJumpPlaceholder.class.st
index 4a09519..3253d6d 100644
--- a/packages/DomainCode-Parser/DCJumpPlaceholder.class.st
+++ b/packages/DomainCode-Parser/DCJumpPlaceholder.class.st
@@ -44,6 +44,12 @@ DCJumpPlaceholder >> pasteReplace [
 			do: [:new :edit | self applyEdit: edit source: new cursorAt: cursorIndex + str size]]
 ]
 
+{ #category : #'as yet unclassified' }
+DCJumpPlaceholder >> type [
+
+	^ #identifier
+]
+
 { #category : #'as yet unclassified' }
 DCJumpPlaceholder >> valid [
 
diff --git a/packages/DomainCode-Parser/DCQueryState.class.st b/packages/DomainCode-Parser/DCQueryState.class.st
index 534d05e..6e6e253 100644
--- a/packages/DomainCode-Parser/DCQueryState.class.st
+++ b/packages/DomainCode-Parser/DCQueryState.class.st
@@ -122,7 +122,9 @@ DCQueryState >> queueUpdateQueriesFor: aSymbol [
 { #category : #'as yet unclassified' }
 DCQueryState >> reportError: aDecorator for: aBlock [
 
-	(newDecorators at: aBlock ifAbsentPut: [OrderedCollection new]) add: aDecorator
+	| errors |
+	errors := newDecorators at: aBlock ifAbsentPut: [OrderedCollection new].
+	(errors noneSatisfy: [:e | e message = aDecorator message]) ifTrue: [errors add: aDecorator]
 ]
 
 { #category : #'as yet unclassified' }
diff --git a/packages/DomainCode-Parser/DCSmalltalkMethod.class.st b/packages/DomainCode-Parser/DCSmalltalkMethod.class.st
index 60756bd..2febc16 100644
--- a/packages/DomainCode-Parser/DCSmalltalkMethod.class.st
+++ b/packages/DomainCode-Parser/DCSmalltalkMethod.class.st
@@ -19,6 +19,12 @@ DCSmalltalkMethod class >> for: aCompiledMethod [
 	^ aCompiledMethod isSandblock ifFalse: [self new for: aCompiledMethod] ifTrue: [self new emptyIn: aCompiledMethod methodClass]
 ]
 
+{ #category : #'as yet unclassified' }
+DCSmalltalkMethod class >> newWith: aString in: aClass [
+
+	^ self new in: aClass with: aString
+]
+
 { #category : #'as yet unclassified' }
 DCSmalltalkMethod >> browse [
 	<action>
@@ -26,6 +32,12 @@ DCSmalltalkMethod >> browse [
 	Browser newOnClass: self methodClass selector: self selector
 ]
 
+{ #category : #'as yet unclassified' }
+DCSmalltalkMethod >> category [
+
+	^ self methodClass organization categoryOfElement: self selector
+]
+
 { #category : #'as yet unclassified' }
 DCSmalltalkMethod >> emptyIn: aClass [
 
@@ -60,6 +72,13 @@ DCSmalltalkMethod >> ignoreChangeNotifierDuring: aBlock [
 	aBlock ensure: [self removeProperty: #ignoreChangeNotifier]
 ]
 
+{ #category : #'as yet unclassified' }
+DCSmalltalkMethod >> in: aClass with: aString [
+
+	methodClass := aClass.
+	self addMorphBack: (DCBlock parseBlock: aString language: SBTSSmalltalk)
+]
+
 { #category : #'as yet unclassified' }
 DCSmalltalkMethod >> initialize [
 
@@ -134,6 +153,12 @@ DCSmalltalkMethod >> object [
 		ifAbsent: [self]
 ]
 
+{ #category : #'as yet unclassified' }
+DCSmalltalkMethod >> relatedClass [
+
+	^ self methodClass
+]
+
 { #category : #'as yet unclassified' }
 DCSmalltalkMethod >> reloadMethodInPlaceUndoable: aBoolean [
 
@@ -159,7 +184,10 @@ DCSmalltalkMethod >> saveTryFixing: aFixBoolean quick: aQuickBoolean [
 		ifTrue: [self externalModification: false]
 		ifFalse: [^ false].
 	
-	self firstSubmorph queryState errorsDo: [:error | aFixBoolean ifTrue: [error tryFixIfFail: [^ false]] ifFalse: [^ false]].
+	self firstSubmorph queryState errorsDo: [:error |
+		aFixBoolean ifTrue: [error tryFixIfFail: [^ false]] ifFalse: [^ false].
+		"errors are applied and removed on the next tick only"
+		self world ifNotNil: #doOneCycleNow].
 	
 	text := aQuickBoolean ifTrue: [self method sourceString] ifFalse: [
 		[
@@ -173,7 +201,7 @@ DCSmalltalkMethod >> saveTryFixing: aFixBoolean quick: aQuickBoolean [
 	self ignoreChangeNotifierDuring: [
 		newSelector := self methodClass
 			compile: text withSqueakLineEndings asText
-			classified: nil].
+			classified: self category].
 	
 	^ true
 ]
@@ -182,7 +210,7 @@ DCSmalltalkMethod >> saveTryFixing: aFixBoolean quick: aQuickBoolean [
 DCSmalltalkMethod >> selector [
 
 	| selector |
-	selector := (self method queryAll: '[(unary_selector) (binary_selector) (keyword_selector)] @') first.
+	selector := (self method queryAll: '[(unary_selector) (binary_selector) (keyword_selector)] @') ifEmpty: [^ ''] ifNotEmpty: #first.
 	
 	^ (((selector childSandblocks viewFrom: 1 by: 2) collect: [:p | p contents]) joinSeparatedBy: '') asSymbol
 ]
diff --git a/packages/DomainCode-Parser/DCText.class.st b/packages/DomainCode-Parser/DCText.class.st
index f35bd96..3619a45 100644
--- a/packages/DomainCode-Parser/DCText.class.st
+++ b/packages/DomainCode-Parser/DCText.class.st
@@ -104,6 +104,12 @@ DCText >> initialize [
 	range := SBTSRange null
 ]
 
+{ #category : #'as yet unclassified' }
+DCText >> isExpression [
+
+	^ false
+]
+
 { #category : #'as yet unclassified' }
 DCText >> isReplacement [
 
diff --git a/packages/Sandblocks-TSSmalltalk/SBTSSmalltalk.class.st b/packages/Sandblocks-TSSmalltalk/SBTSSmalltalk.class.st
index 590f5f6..b04c486 100644
--- a/packages/Sandblocks-TSSmalltalk/SBTSSmalltalk.class.st
+++ b/packages/Sandblocks-TSSmalltalk/SBTSSmalltalk.class.st
@@ -1305,10 +1305,7 @@ SBTSSmalltalk class >> spaceBetween: aBlock and: anotherBlock lastCharacterOfFir
 	(aBlock type = 'string' and: [anotherBlock type = 'string']) ifTrue: [^ true].
 	anotherBlock type = #'block_argument' ifTrue: [^ true].
 	aCharacter = $: ifTrue: [^ true].
-	(anotherBlock type = 'ERROR' and: [
-		anotherBlock firstDeepChild contents
-			ifNotEmpty: [:e | e first isLetter not]
-			ifEmpty: [false]]) ifTrue: [^ false].
+	"( anotherBlock type ='ERROR' and: [ anotherBlock firstDeepChild contents ifNotEmpty: [ :e| e first isLetter not ]ifEmpty: [ false ] ] )ifTrue: [ ^false ]"
 	(aBlock contents = ':=' or: [anotherBlock contents = ':=']) ifTrue: [^ true].
 	anotherBlock alias = #'unary_identifier' ifTrue: [^ true].
 	^ super spaceBetween: aBlock and: anotherBlock lastCharacterOfFirst: aCharacter
diff --git a/packages/Sandblocks-TreeSitter/SBTSGrammar.class.st b/packages/Sandblocks-TreeSitter/SBTSGrammar.class.st
index a422488..1f5bdd7 100644
--- a/packages/Sandblocks-TreeSitter/SBTSGrammar.class.st
+++ b/packages/Sandblocks-TreeSitter/SBTSGrammar.class.st
@@ -357,6 +357,14 @@ SBTSGrammar >> inlinedRules [
 	^ inlinedRules
 ]
 
+{ #category : #testing }
+SBTSGrammar >> is: aSymbol subtypeOf: anotherSymbol [
+
+	self assert: (self isSuperType: anotherSymbol).
+	aSymbol = anotherSymbol ifTrue: [^ true].
+	^ (self bodyNodeForRule: anotherSymbol) allSubTypesRecursive anySatisfy: [:node | node type = aSymbol]
+]
+
 { #category : #testing }
 SBTSGrammar >> isBlockInlined: aSymbol [
 
diff --git a/packages/Sandblocks-TreeSitter/SBTSLanguage.class.st b/packages/Sandblocks-TreeSitter/SBTSLanguage.class.st
index 113550f..498a5fa 100644
--- a/packages/Sandblocks-TreeSitter/SBTSLanguage.class.st
+++ b/packages/Sandblocks-TreeSitter/SBTSLanguage.class.st
@@ -146,6 +146,12 @@ SBTSLanguage class >> emptyLineSymbol [
 	^ #empty
 ]
 
+{ #category : #configuration }
+SBTSLanguage class >> expressionTypes [
+
+	^ #(#expression)
+]
+
 { #category : #'loading - helper' }
 SBTSLanguage class >> fetchLibrary: aGithubString branch: aString [
 
diff --git a/packages/Sandblocks-TreeSitter/SBTSNodeBase.class.st b/packages/Sandblocks-TreeSitter/SBTSNodeBase.class.st
index cd30691..a18ac49 100644
--- a/packages/Sandblocks-TreeSitter/SBTSNodeBase.class.st
+++ b/packages/Sandblocks-TreeSitter/SBTSNodeBase.class.st
@@ -57,6 +57,19 @@ SBTSNodeBase >> allSubTypesDo: aBlock parents: aCollection [
 	
 ]
 
+{ #category : #hierarchy }
+SBTSNodeBase >> allSubTypesRecursive [
+
+	| found pending |
+	found := OrderedCollection new.
+	pending := OrderedCollection with: self.
+	[pending notEmpty] whileTrue: [
+		pending removeFirst allSubTypes do: [:type |
+			found add: type.
+			pending add: type]].
+	^ found
+]
+
 { #category : #hierarchy }
 SBTSNodeBase >> allSuperTypesDo: aBlock [