langref: add missing return types to builtin functions

This should add all remaining missing return types to all builtin
functions.
For @clz, @ctz, and @popcount it uses anytype for the lack of a better
alternative. We already use this return type for other builtin functions in the langref
to indicate that the type is not always the same.
It is not possible to use anytype as the return type for regular
functions but builtin functions are special.

Author: wooster0

doc/langref.html.in

@@ -7814,7 +7814,7 @@ comptime {
       {#header_close#}
 
       {#header_open|@breakpoint#}
-      <pre>{#syntax#}@breakpoint(){#endsyntax#}</pre>
+      <pre>{#syntax#}@breakpoint() void{#endsyntax#}</pre>
       <p>
       This function inserts a platform-specific debug trap instruction which causes
       debuggers to break there.
@@ -7933,7 +7933,7 @@ pub const CallModifier = enum {
       {#header_close#}
 
       {#header_open|@cDefine#}
-      <pre>{#syntax#}@cDefine(comptime name: []u8, value){#endsyntax#}</pre>
+      <pre>{#syntax#}@cDefine(comptime name: []u8, value) void{#endsyntax#}</pre>
       <p>
       This function can only occur inside {#syntax#}@cImport{#endsyntax#}.
       </p>
@@ -7977,7 +7977,7 @@ pub const CallModifier = enum {
       {#see_also|Import from C Header File|@cInclude|@cDefine|@cUndef#}
       {#header_close#}
       {#header_open|@cInclude#}
-      <pre>{#syntax#}@cInclude(comptime path: []u8){#endsyntax#}</pre>
+      <pre>{#syntax#}@cInclude(comptime path: []u8) void{#endsyntax#}</pre>
       <p>
       This function can only occur inside {#syntax#}@cImport{#endsyntax#}.
       </p>
@@ -7989,7 +7989,7 @@ pub const CallModifier = enum {
       {#header_close#}
 
       {#header_open|@clz#}
-      <pre>{#syntax#}@clz(operand: anytype){#endsyntax#}</pre>
+      <pre>{#syntax#}@clz(operand: anytype) anytype{#endsyntax#}</pre>
       <p>{#syntax#}@TypeOf(operand){#endsyntax#} must be an integer type or an integer vector type.</p>
       <p>{#syntax#}operand{#endsyntax#} may be an {#link|integer|Integers#} or {#link|vector|Vectors#}.</p>
       <p>
@@ -8068,7 +8068,7 @@ fn cmpxchgWeakButNotAtomic(comptime T: type, ptr: *T, expected_value: T, new_val
       {#header_close#}
 
       {#header_open|@compileError#}
-      <pre>{#syntax#}@compileError(comptime msg: []u8){#endsyntax#}</pre>
+      <pre>{#syntax#}@compileError(comptime msg: []u8) noreturn{#endsyntax#}</pre>
       <p>
       This function, when semantically analyzed, causes a compile error with the
       message {#syntax#}msg{#endsyntax#}.
@@ -8081,7 +8081,7 @@ fn cmpxchgWeakButNotAtomic(comptime T: type, ptr: *T, expected_value: T, new_val
       {#header_close#}
 
       {#header_open|@compileLog#}
-      <pre>{#syntax#}@compileLog(args: ...){#endsyntax#}</pre>
+      <pre>{#syntax#}@compileLog(args: ...) void{#endsyntax#}</pre>
       <p>
       This function prints the arguments passed to it at compile-time.
       </p>
@@ -8139,7 +8139,7 @@ test "main" {
       {#header_close#}
 
       {#header_open|@ctz#}
-      <pre>{#syntax#}@ctz(operand: anytype){#endsyntax#}</pre>
+      <pre>{#syntax#}@ctz(operand: anytype) anytype{#endsyntax#}</pre>
       <p>{#syntax#}@TypeOf(operand){#endsyntax#} must be an integer type or an integer vector type.</p>
       <p>{#syntax#}operand{#endsyntax#} may be an {#link|integer|Integers#} or {#link|vector|Vectors#}.</p>
       <p>
@@ -8159,7 +8159,7 @@ test "main" {
       {#header_close#}
 
       {#header_open|@cUndef#}
-      <pre>{#syntax#}@cUndef(comptime name: []u8){#endsyntax#}</pre>
+      <pre>{#syntax#}@cUndef(comptime name: []u8) void{#endsyntax#}</pre>
       <p>
       This function can only occur inside {#syntax#}@cImport{#endsyntax#}.
       </p>
@@ -8370,7 +8370,7 @@ export fn @"A function name that is a complete sentence."() void {}
       {#header_close#}
 
       {#header_open|@fence#}
-      <pre>{#syntax#}@fence(order: AtomicOrder){#endsyntax#}</pre>
+      <pre>{#syntax#}@fence(order: AtomicOrder) void{#endsyntax#}</pre>
       <p>
       The {#syntax#}fence{#endsyntax#} function is used to introduce happens-before edges between operations.
       </p>
@@ -8622,7 +8622,7 @@ test "integer cast panic" {
       {#header_close#}
 
       {#header_open|@memcpy#}
-      <pre>{#syntax#}@memcpy(noalias dest: [*]u8, noalias source: [*]const u8, byte_count: usize){#endsyntax#}</pre>
+      <pre>{#syntax#}@memcpy(noalias dest: [*]u8, noalias source: [*]const u8, byte_count: usize) void{#endsyntax#}</pre>
       <p>
       This function copies bytes from one region of memory to another. {#syntax#}dest{#endsyntax#} and
           {#syntax#}source{#endsyntax#} are both pointers and must not overlap.
@@ -8641,7 +8641,7 @@ mem.copy(u8, dest[0..byte_count], source[0..byte_count]);{#endsyntax#}</pre>
       {#header_close#}
 
       {#header_open|@memset#}
-      <pre>{#syntax#}@memset(dest: [*]u8, c: u8, byte_count: usize){#endsyntax#}</pre>
+      <pre>{#syntax#}@memset(dest: [*]u8, c: u8, byte_count: usize) void{#endsyntax#}</pre>
       <p>
       This function sets a region of memory to {#syntax#}c{#endsyntax#}. {#syntax#}dest{#endsyntax#} is a pointer.
       </p>
@@ -8753,7 +8753,7 @@ test "@wasmMemoryGrow" {
       {#header_close#}
 
       {#header_open|@popCount#}
-      <pre>{#syntax#}@popCount(operand: anytype){#endsyntax#}</pre>
+      <pre>{#syntax#}@popCount(operand: anytype) anytype{#endsyntax#}</pre>
       <p>{#syntax#}@TypeOf(operand){#endsyntax#} must be an integer type.</p>
       <p>{#syntax#}operand{#endsyntax#} may be an {#link|integer|Integers#} or {#link|vector|Vectors#}.</p>
       <p>Counts the number of bits set in an integer.</p>
@@ -8767,7 +8767,7 @@ test "@wasmMemoryGrow" {
       {#header_close#}
 
       {#header_open|@prefetch#}
-      <pre>{#syntax#}@prefetch(ptr: anytype, comptime options: std.builtin.PrefetchOptions){#endsyntax#}</pre>
+      <pre>{#syntax#}@prefetch(ptr: anytype, comptime options: std.builtin.PrefetchOptions) void{#endsyntax#}</pre>
       <p>
       This builtin tells the compiler to emit a prefetch instruction if supported by the
       target CPU. If the target CPU does not support the requested prefetch instruction,
@@ -8881,21 +8881,21 @@ pub const PrefetchOptions = struct {
       {#header_close#}
 
       {#header_open|@setAlignStack#}
-      <pre>{#syntax#}@setAlignStack(comptime alignment: u29){#endsyntax#}</pre>
+      <pre>{#syntax#}@setAlignStack(comptime alignment: u29) void{#endsyntax#}</pre>
       <p>
       Ensures that a function will have a stack alignment of at least {#syntax#}alignment{#endsyntax#} bytes.
       </p>
       {#header_close#}
 
       {#header_open|@setCold#}
-      <pre>{#syntax#}@setCold(comptime is_cold: bool){#endsyntax#}</pre>
+      <pre>{#syntax#}@setCold(comptime is_cold: bool) void{#endsyntax#}</pre>
       <p>
       Tells the optimizer that a function is rarely called.
       </p>
       {#header_close#}
 
       {#header_open|@setEvalBranchQuota#}
-      <pre>{#syntax#}@setEvalBranchQuota(comptime new_quota: u32){#endsyntax#}</pre>
+      <pre>{#syntax#}@setEvalBranchQuota(comptime new_quota: u32) void{#endsyntax#}</pre>
       <p>
       Changes the maximum number of backwards branches that compile-time code
       execution can use before giving up and making a compile error.
@@ -8930,7 +8930,7 @@ test "foo" {
       {#header_close#}
 
       {#header_open|@setFloatMode#}
-      <pre>{#syntax#}@setFloatMode(comptime mode: @import("std").builtin.FloatMode){#endsyntax#}</pre>
+      <pre>{#syntax#}@setFloatMode(comptime mode: @import("std").builtin.FloatMode) void{#endsyntax#}</pre>
       <p>
       Sets the floating point mode of the current scope. Possible values are:
       </p>