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Author	SHA1	Message	Date
Daniel Grunwald	5526400b17	Extend InferType() to every ILInstruction Change InferType() to an abstract method and implement for every ILInstruction. With this change, we now always have enough information to create a variable of an appropriate type to store the result of evaluating the instruction. This previously was not the case for instructions producing "other value type", for which the stacktype-based fallback incorrectly produced `object`.	2 weeks ago
Siegfried Pammer	d22d4301e4	Expand nested conditional operators back into if-else HandleConditionalOperator collapses `if (c) a = x; else a = y;` into a conditional operator, innermost first, and keeps going for as long as the chain does. A source else-if ladder therefore comes back as one expression, however long it was: the sample in #2027 decompiles to a single 2095-character statement, and one NLog method to 2230 characters nested 29 brackets deep. ExpandNestedConditionals undoes that past one level, so a statement keeps at most a single conditional operator. It runs at the end of the pipeline rather than inside ExpressionTransforms, because every transform that needs its input to be a single expression has to see the collapsed form first: object and collection initializers, `with`, switch expressions, interpolated string handlers, and the query lambdas the C# stage later rewrites into clauses. Cutting the chain earlier leaves an if-else between the statements they pattern-match on and they silently stop matching - an object initializer assigning an init-only member then does not even compile. The same reasoning ReduceNestingTransform gives for walking back ConditionDetection's aggressive else-inlining once the structure is settled. A chain already stored to a variable is expanded into that variable, so nothing has to be decided: the variable carries its own type. A chain in any other position - an argument, a return value, a field store - has nothing to expand into, and ILExtraction can give it one. The temporary ILExtraction creates is typed from the stack type though, where `I4` is `int`, `bool`, `char` and every enum at once, so extracting on that basis turned a bool into `int num` with `if (num == 0)` and an enum into `dbType = (IsFixedLength ? 22 : 0)`. InferExpectedType is the counterpart to InferType that answers this: where InferType asks what a value is, it asks what the position the value flows into says it should be - a parameter, a return type, a field, all of which carry their type in metadata. Extraction is done only where that question has an answer, and the temporary is typed from it. The receiver of a call then reads `XPathNavigator xPathNavigator`, not `object obj` with a cast back, and a field store keeps its enum's member names. The Pretty fixture covers what must NOT change: an array initializer, a query lambda, a ref local, a switch expression, an object initializer with an init-only member, a `with` expression, a catch-when filter and both constructor-initializer forms. The positive case is an ILPretty test, because a Pretty fixture is its own input and expected output, and a chain that round-trips through collapse and expansion has no fixed point there. The PdbGen test records the cost in breakpoints: the compiler's single sequence point for the collapsed statement becomes one per expanded statement, which is inherent to splitting a statement in two. #2027 Assisted-by: Claude:claude-opus-5:Claude Code	3 weeks ago

Author

SHA1

Message

Date

Daniel Grunwald

5526400b17

Extend InferType() to every ILInstruction

Change InferType() to an abstract method and implement for every ILInstruction.
With this change, we now always have enough information to create a variable of an appropriate type to store the result of evaluating the instruction.
This previously was not the case for instructions producing "other value type", for which the stacktype-based fallback incorrectly produced `object`.

2 weeks ago

Siegfried Pammer

d22d4301e4

Expand nested conditional operators back into if-else

HandleConditionalOperator collapses `if (c) a = x; else a = y;` into a
conditional operator, innermost first, and keeps going for as long as the
chain does. A source else-if ladder therefore comes back as one expression,
however long it was: the sample in #2027 decompiles to a single
2095-character statement, and one NLog method to 2230 characters nested 29
brackets deep.

ExpandNestedConditionals undoes that past one level, so a statement keeps at
most a single conditional operator.

It runs at the end of the pipeline rather than inside ExpressionTransforms,
because every transform that needs its input to be a single expression has
to see the collapsed form first: object and collection initializers, `with`,
switch expressions, interpolated string handlers, and the query lambdas the
C# stage later rewrites into clauses. Cutting the chain earlier leaves an
if-else between the statements they pattern-match on and they silently stop
matching - an object initializer assigning an init-only member then does not
even compile. The same reasoning ReduceNestingTransform gives for walking
back ConditionDetection's aggressive else-inlining once the structure is
settled.

A chain already stored to a variable is expanded into that variable, so
nothing has to be decided: the variable carries its own type. A chain in any
other position - an argument, a return value, a field store - has nothing to
expand into, and ILExtraction can give it one. The temporary ILExtraction
creates is typed from the stack type though, where `I4` is `int`, `bool`,
`char` and every enum at once, so extracting on that basis turned a bool
into `int num` with `if (num == 0)` and an enum into
`dbType = (IsFixedLength ? 22 : 0)`.

InferExpectedType is the counterpart to InferType that answers this: where
InferType asks what a value is, it asks what the position the value flows
into says it should be - a parameter, a return type, a field, all of which
carry their type in metadata. Extraction is done only where that question
has an answer, and the temporary is typed from it. The receiver of a call
then reads `XPathNavigator xPathNavigator`, not `object obj` with a cast
back, and a field store keeps its enum's member names.

The Pretty fixture covers what must NOT change: an array initializer, a
query lambda, a ref local, a switch expression, an object initializer with
an init-only member, a `with` expression, a catch-when filter and both
constructor-initializer forms. The positive case is an ILPretty test,
because a Pretty fixture is its own input and expected output, and a chain
that round-trips through collapse and expansion has no fixed point there.
The PdbGen test records the cost in breakpoints: the compiler's single
sequence point for the collapsed statement becomes one per expanded
statement, which is inherent to splitting a statement in two.

#2027

Assisted-by: Claude:claude-opus-5:Claude Code

3 weeks ago

2 Commits (052aec9b89a8d79a50cb176b2a162c2ce676dafa)